T. Lori Stewart. CARBONATE PETROLOGY AND SEDIMENTOLOGY OF THE MIOCENE
FUNGO RIVER FORMATION, ONSLOW BAY, NORTH CAROLINA CONTINENTAL SHELF.
(Under the direction of Dr. Stanley R. Riggs) Department of Geology,
December 1985.
The Pungo River Formation in Onslow Bay,. North Carolina is
predominantly a slliciclastic sediment sequence with variable amounts of
authigenic and diagenetlc minerals including carbonates. Based on
examination of 14 of the 16 outcropping Pungo River seismic units, the
dominant carbonate component is carbonate mud (low-Mg calclte, dolomite,
or a mixture of the two). Calcareous fossils are the next most abundant
carbonate component. Calcite cements are a very minor component and are
only locally abundant.
Four patterns of carbonate sedimentation occur in the Pungo River
Formation in Onslow Bay. 1) Cyclic carbonate sediments overlying
noncarbonate lithologies and deposited as a couplet during the same
fourth-order sea-level cycle are common. Biomicrosparites which grade
into phosphorites of seismic unit FPF-1 represent deposition during a
fourth-order sea-level maximum when warm Gulf Stream waters flooded the
shelf. Calcite-cemented sandstone of BBF-2 grades down section into
unindurated quartz sand. Unlndurated, muddy, barnacle-rich sands
represent fourth-order sea-level regressions. These types of carbonate
cap rocks conform to the idealized llthic cycle of the Riggs model of
Neogene sedimentation (1984).
2) Sediments of the AF seismic sequence are largely carbonates in
northern Onslow Bay and siliciclastlcs in central Onslow Bay.
Carbonate content in each fourth-order seismic unit increases up section
from AF-1 to AF-4. AF-1 in northern Onslow Bay represents mid to outer
shelf sedimentation. AF-2 and AF-3 contain a predominantly reworked
fossil assemblage. AF-4 is a barnacle hash, representing formation on
shelf edge hardgrounds and deposition off the shelf edge.
3) Sparse fossils and minor carbonate mud occur disseminated in all
predominantly noncarbonate lithologies. The major source of calcareous
mud is probably from bio-mechanical degradation of larger carbonate
grains, primarily shell material.
4) Predominantly carbonate beds interbedded with noncarbonate
lithologies include: moldic microsparite which probably represents the
carbonate cap on FPF-1 in northern Onslow Bay; moldic microsparite in
BBF-1 which may be similar in origin to the carbonate cap of unit C in
the Aurora Area; and echinold-foramlniferal blosparltes in FPF-6, which
probably formed by winnowing of the fines by marine currents such as
Gulf Stream eddies.
Dlagenetic carbonates (calcite cements and dolomite) and silicates
(opal-CT, microcrystalline quartz, and clinoptllolite) exhibit vertical
dlagenetic profiles in some cores. Where carbonate sediments are
abundant, effects of fresh water calcite cementation decrease down
section. Because syntaxlal cement on echinoids is precipitated faster
than rim cements on other fossils, it is a good indicator of the degree
of diagenesis undergone by sediments. Dolomite abundance and
distribution are sporadic, prehaps reflecting presence or absence of
sulfate reducing bacteria in the sediment. Local chert nodule formation
is related to abundance of siliceous fossils and to permeability
barriers within the sediments.
CARBONATE PETROLOGY AND SEDIMENTOLOGY
OF THE MIOCENE PUNGO RIVER FORMATION,
ONSLOW BAY, NORTH CAROLINA CONTINENTAL SHELF
A Thesis
Presented to
the Faculty of the Department of Geology
East Carolina University
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Geology
by
T. Lori Stewart
December 1985
CARBONATE PETROLOGY AND SEDIMENTOLOGY
OF THE MIOCENE PUNGO RIVER FORMATION,
ONSLOW BAY, NORTH CAROLINA CONTINENTAL SHELF
by
T. Lori Stewart
APPROVED BY:
COMMITTEE
áííM. k<w.
Dr. Albert C. Hine
University of South Florida
CHAIRMAN OF THE DEPARTMENT OF GEOLOGY
Dr
DEAN OF THE GRADUATE SCHOOL
ACKNOWLEDGEMENTS
Financial support for this research was provided through National
Science Foundation grants OCE-7908949, OCE-8110907, and OCE-8342777 to
co-investigators Stanley R. Riggs and Albert C. Hlne. The North
Carolina Department of Natural Resources and Community Development,
Geological Survey Section, provided partial funding toward the
completion of this study.
I would like to express ray sincere gratitude to Dr. Stan Riggs for
all of his guidance, encouragement, and support during the evolution of
this thesis. Many thanks are extended to Drs. Don Neal and Scott Snyder
for their assistance as thesis committee members and to Dr. A1 Mine of
the University of South Florida for serving as outside reader.
I am very grateful to Dr. Victor Zullo of the University of North
Carolina at Wilmington for his identification of the barnacles and his
invaluble help in helping me to understand what "barnacliferous"
sediments mean.
I would especially like to thank Brian Gray and Don Neal for their
many thought provoking discussions on anything from dirty carbonates to
silicification. I would also like to acknowledge the contributions of
Tim Mooring, Mitch Landen, Mike Lyle, Randy Powers, Walter Hale, Teri
Moore, Doug Ellington, and Pat Mallette.
To my parents, I dedicate this thesis. Their love and support have
made it possible for me to complete my tenure as a graduate student at
ECU
TABLE OF CONTENTS
PAGE
INTRODUCTION 1
THE NORTH CAROLINA MIOCENE 4
Structural Setting 4
Stratigraphy 7
Coastal Plain 7
Continental Shelf 10
OBJECTIVES 18
METHODS OF INVESTIGATION 19
Sampling 19
Textural Analysis 19
Reflected Light Microscopy . 19
Insoluble Residue Analysis 23
X-Ray Dlf frac tome try 24
Thin Section Analysis 24
Scanning Electron Microscopy 25
PETROLOGY 26
Deposltlonal Components 26
Carbonate Allochems ... 26
Arthropods 26
Molluscs 33
Echlnoderms 33
Foramlnlfers 33
Bryozoans 34
Algae 34
Brachlopods 34
Coated Grains 34
Others 36
Siliceous Allochems 36
Phosphate Allochems 38
Glauconite 39
Slllclclastlc Sands 39
Matrix 39
Dlagenetlc Components 40
Introduction 40
Calclte Cements 42
Radial Rim Cements 42
Syntaxlal Cement 44
Pore Filling Cements 45
Microspar 48
Dolomite 51
Silicification 61
Zeolites 73
Summary 76
LITHOLOGIC DESCRIPTIONS 78
FPF Sequence 78
Seismic Unit FPF-1 78
Seismic Unit FPF-2 84
Seismic Unit FPF-3 86
Seismic Unit FPF-4 89
Seismic Unit FPF-5 89
Seismic Unit FPF-6 91
Summary 93
AF Sequence 97
Seismic Unit ÂF-1 97
Seismic Unit ÂF-2 101
Seismic Unit AF-3 104
Seismic Unit AF-4 104
Summary 106
BBF Sequence ..... 108
Seismic Unit BBF-1 108
Seismic Unit BBF-2 113
Seismic Unit BBF-3 116
Seismic Unit BBF-6 116
DISCUSSION 117
Cyclic Patterns of Carbonate Sedimentation 117
Carbonates Associated with the Idealized Cycle of Riggs 117
Barnacle-rich Carbonates 120
Barnacle Ecology 121
Inner Shelf Deposits 122
Outer Shelf-Slope Deposits 126
Carbonates in Noncarbonate Lithologies 130
Disseminated Carbonates ... 130
Interbedded Carbonates 132
Echinold-foraminlferal Biosparites 132
Moldlc Mlcrosparltes 133
SUMMARY 136
REFERENCES CITED 143
APPENDIX A - Reflected Light Microscopy Data 152
APPENDIX B - Insoluble Residue and X-ray Diffraction Data . . . 158
APPENDIX C - Thin Section Point Count Data 164
APPENDIX D - Textural Data 168
LIST OF TABLES
TABLE PAGE
1. Summary of the Pungo River carbonate sediments
described by Lewis (1981) 17
2. Summarization of sample analyses 21
3. Average composition of Pungo River sediments in
Onslow Bay 27
4. Compositional ranges of Pungo River sediments in
Onslow Bay 28
5. Abundances of diagenetic components 41
6. Distribution and abundance of dolomite 56
7. Major superstructure reflections of dolomite,
ankerite, and Pungo River dolomite 57
8. Microprobe analysis of dolomite from core OB-1
(seismic unit BBF-6) 59
9. Summary of abundance and distribution of mineralogical
and faunal components in FPF seismic units along each
seismic profile 79
10. Summary of major mineralogical components in the FPF
seismic units 80
11. Composition of the FPF-1 carbonate cap 82
12. Summary of abundance and distribution of mineralogical
and faunal components in AF seismic units along each
seismic profile 98
13. Summary of major mineralogical components in the AF
seismic units 99
14. Summary of abundance and distribution of mineralogical
and faunal components in BBF seismic units along each
seismic profile 109
15. Summary of major mineralogical components in the BBF
seismic units 110
16. Neogene sedimentation model for the southeastern
United States (Riggs, 198A) 119
17. Composition of barnacle cap rocks 124
18. Composition of moldlc mlcrosparltes 134
LIST OF FIGURES
FIGURE PAGE
1. Geologic map showing the subcrop pattern of Miocene
seismic sequences in Onslow Bay, N.C 2
2. Geologic map showing the location of the Mid-Carolina
Platform High and the outcrop pattern of Cretaceous
and Tertiary sediments 5
3. Structural contour map on the base of the Pungo River
Formation and the Miocene phosphate districts of the
southeastern North Carolina continental margin 6
4. Average concentrations of phosphate, siliciclastic, and
carbonate sediments from cores in the Aurora Area, N.C. ... 8
5. Chart showing the relationship of seismic sequences
present in Onslow Bay to relative global sea-level 12
6. Interpreted seismic profile through the Frying Pan Area ... 14
7. Interpreted seismic profiles through northern Onslow Bay . . 15
8. Map of Onslow Bay showing location of vibracores used in
this study and seismic lines discussed in text 20
9. Vertical distribution of siliceous fossils and chert
nodules in FPF-2, core OB-47 72
10. Relative timing of dlagenetic events 77
11. Vertical distribution of major mlneraloglcal components
in FPF-1, core OB-115 83
12. Lateral distribution of carbonate components in FPF-1 .... 85
13. Lateral distribution of siliciclastic components in FPF-1 . . 85
14. Vertical distribution of zeolites and foraminifers
in FPF-2, core OB-27 87
15. Lateral distribution of carbonate components in FPF-2 .... 88
16. Lateral distribution of siliciclastic components in FPF-2 . . 88
17. Lateral distribution of carbonate components in FPF-3 .... 90
18. Lateral distribution of siliciclastic components in FPF-3 . . 90
19. Lateral distribution of carbonate components in FPF-5 .... 92
20. Lateral distribution of siliciclastic components in FPF-5 . . 92
21. Lateral distribution of carbonate components in FPF-6 .... 94
22. Lateral distribution of siliciclastic components in FPF-6 . . 94
23. Lateral distribution of carbonate components in each
FPF seismic unit 95
24. Average carbonate content of the FPF sequence 95
25. Lateral distribution of carbonate components in AF-1 .... 102
26. Lateral distribution of siliciclastic components in AF-1 . . 102
27. Lateral distribution of carbonate components in AF-2 .... 103
28. Lateral distribution of siliciclastic components in AF-2 . . 103
29. Lateral distribution of carbonate components in AF-3 .... 105
30. Lateral distribution of siliciclastic components in AF-3 . . 105
31. Lateral distribution of carbonate components in each
AF seismic unit 107
32. Average carbonate content of the AF sequence 107
33. Lateral distribution of carbonate components in BBF-1 .... 114
34. Lateral distribution of siliciclastic and phosphatlc
components in BBF-1 114
35. Vertical distribution of carbonate and siliciclastic
components in BBF-2, core OB-92 115
36. Barnacle depositlonal model during transgression 125
37. Barnacle depositlonal model during regression 127
38. Sand-size siliceous vs. calcareous fossils 131
39. Sand-size siliceous fossils vs. matrix 131
40. Map of the Pungo River Formation showing the distribution
of carbonate sediments 137
41. Map of the Pungo River Formation showing the distribution
of carbonate mud 138
42. Map of the Pungo River Formation showing the distribution
of calcareous fossil assemblages 139
LIST OF PLATES
PLATE PAGE
1. Washed sediment of FPF-6, core OB-45 30
2. Washed sediment of FPF-1, core OB-115 30
3. Barnacle plates 31
4. Carbonate cap rock of FPF-1, core OB-115 31
5. Washed sediment of AF-1, core OB-35 32
6. Washed sediment of FPF-6, core OB-96 32
7. Coralline red algae 35
8. Washed sediment of AF-1, core OB-34 37
9. Diatomaceous mud 37
10. Isopachous rim cement ....... 43
11. Syntaxial cement 46
12. SEM photomicrograph of well preserved echinold
plate fragment 46
13. SEM photomicrograph of early stage syntaxial
cement on echinoid plate fragment 47
14. SEM photomicrograph of later stage syntaxial
cement on echinoid plate fragment 47
15. Blocky pore filling cement and microspar 49
16. Drusy pore filling cement 49
17. Euhedral dolomite rhombs 52
18. SEM photomicrograph of euhedral dolomite rhombs 52
19. SEM photomicrograph of dolomite rhombs showing
dissolution pitting 53
20. SEM photograph of dolomite rhomb showing "flame-texture"
and dissolution pitting 53
21. Zoned dolomite In chert nodule 55
22. SEM photomicrograph of hollow dolomite in chert nodule ... 55
23. Chert nodule from core OB-35, seismic unit AF-1 63
24. Photomicrograph of chert 64
25. Photomicrograph of chert 64
26. Void lining chalcedony 65
27. Clay-rich transition zone in chert nodule .. 65
28. Bedding preserved by silicification . 67
29. Contact between area of intense silicification
and rim of chert nodule 67
30. SEM photomicrograph of lepispheres 69
31. SEM photomicrograph of lepispheres ..... 69
32. SEM photomicrograph of spagetti-llke structures
in chert nodules 70
33. Chalcedonlc cement 70
34. Cllnoptilolite-filled internal molds of foraminlfers .... 75
35. SEM photomicrograph of clinoptilollte-ffiled internal
mold of a foraminlfer 75
INTRODUCTION
The Miocene Fungo River Formation is part of a southeast-dipping
sediment wedge that thickens seaward and underlies the coastal plain and
continental shelf of North Carolina. An economically important
sedimentary phosphorite deposit, it correlates with the Hawthorn
Formation of Florida, Georgia, and South Carolina (Riggs, 1984). Gibson
(1967) correlated molluscs and benthic foraminifers of the Fungo River
Formation in the Aurora Area with those of the Calvert Formation, the
basal portion of the Chesapeake Group, in Virginia and Maryland.
The Calvert-Fungo River-Hawthorn complex of the southeastern United
States Atlantic coastal plain and continental shelf contains an
anomalous sequence of authigenlc sediments (Riggs, 1984). Fhosphate
occurs throughout the Miocene section from North Carolina to Florida.
Diatoms increase northward until diatomltes are developed in Virglna.
The southern half of the southeastern Atlantic coastal region contains
abundant palygorskite and sepiolite (Weaver and Beck, 1977), while the
northern half contains abundant cllnoptilollte (Rooney and Kerr, 1967)
and glauconite (Riggs, 1984).
The study area is located in Onslow Bay, an area of approximately
2
10,000 km , on the southeastern North Carolina continental shelf
between Cape Lookout and Cape Fear (Fig. 1). Fungo River sediments crop
out across an area 40 km wide by 150 km long, thicken from 0 m at their
updip erosional limit to over 500 meters at the shelf edge, and dip
gently to the east and southeast (Riggs and others, 1985). In Onslow
Bay, the Fungo River Formation unconformably overlies moldic blomicrltes
2
Figure Geologic map showing the subcrop pattern of seismic
sequences in Onslow Bay, North Carolina continental
shelf (from Riggs and others, 1985).
3
and calcarenites of the Oligocène Belgrade Formation and calcareous
quartz sands of the lower Miocene Silverdale Formation (Baum and others,
1979; Lewis, 1981; S.W.P. Snyder, 1982). The Pungo River Formation is
unconformably overlain by Pliocene and Quaternary sediments.
This study is part of a larger investigation on phosphatic sediment
genesis along the Mid-Atlantic continental margin funded by the National
Science Foundation and coordinated by S.R. Riggs. Other studies address
the seismic stratigraphy, biostratigraphy, paleoecology,
lithostratigraphy, clay mineralogy, phosphate petrology, and
geochemistry of the Pungo River Formation.
This study examines Pungo River carbonate sediments in Onslow Bay,
using Riggs' (1984) depositional model for Neogene phosphates of the
southeastern United States as a frame of reference. The model relates a
systematic change in sedimentation regimes to sea-level and
paleoceanographic changes caused by multiple glacial cycles. An
idealized cyclical sequence of sediments produced in response to each
sea-level cycle would be predominantly siliciclastlc sands at the base,
grade upward into phosphatic sands, and culminate in carbonates. This
model is discussed in greater detail in a later section.
4
THE NORTH CAROLINA MIOCENE
Structural Setting
Tertiary sedimentation in North and South Carolina was controlled
by the Mid-Carolina Platform High (Fig. 2), a topographic high upon the
Carolina Platform, which extends from central Onslow Bay, North Carolina
to Cape Romain, South Carolina (S.W.P. Snyder, 1982; S.W.P. Snyder and
others, 1983). The Carolina Platform is a structural block of
pre-Jurassic crust on the trailing continental margin of North America
and extends from the Baltimore Canyon Trough to the Southeast Georgia
Embayment (Klitgord and Behrendt, 1979; Popenoe, 1983).
Neogene sediments of North Carolina were deposited on the northeast
flank of the Mid-Carolina Platform High. The Cape Lookout High (S.W.P.
Snyder, 1982; Riggs and others, 1985), an east-west trending topographic
high, divided this area into two embayments: Aurora Embayment, in which
the Aurora Phosphate District is located, and Onslow Embayment, in which
my study area is located (Fig. 3). Pungo River sediments in the Aurora
Area are currently being mined for phosphate.
The western updlp limit of Pungo River sediments in the Aurora Area
coincides with a north-south hinge line discussed by Brown and others
(1972) and Miller (1971, 1982). This same north-south line, seismlcally
traced into Onslow Bay, is an ancient erosional scarp with up to 25
meters of relief (S.W.P. Snyder, 1982; S.W.P. Snyder, and others, 1982,
1983), where it is called the White Oak Lineament. Pungo River
sediments thicken abruptly from 20 to 40+ m at the White Oak Lineament
and continue to thicken rapidly downdip to 500+ m in the subsurface at
79*00' 78*00' 77*00' 76*00'
35*00'
34*00'
33*00'
Figure 2. Geologic map showing the location of the Mid-Carolina Platform High
and the outcrop pattern of Cretaceous and Tertiary sediments (from
S.W.P. Snyder, 1982).
6
Figure 3 . Structural contour map on the base of the Pungo River Formation
and the Miocene phosphate districts of the southeastern North
Carolina continental margin (from Riggs and others, 1985).
The represents the location of active phosphate mining.
7
the shelf edge (Riggs and others, 1985). The Pungo River Formation
subcrops beneath surficial veneers of Pliocene and Quaternary sediments
throughout most of Onslow Bay (Fig. 2).
Stratigraphy
Coastal Plain
Phosphatic sediments of the Pungo River Formation have been
extensively studied since Brown (1958) first noted them in Beaufort
County, North Carolina. Kimrey (1964) named the formation and described
the type section from a core near the Pungo River in the vicinity of
Belhaven, Beaufort County, North Carolina. He defined the formation as
a series of Interbedded phosphatic sands, silts, and clays, diatomaceous
clays, and phosphatic limestones. Regional studies by Kimrey (1965),
Miller (1971, 1982), and Brown and others (1972) demonstrated that Pungo
River sediments occur throughout Aurora Embayment. Other investigators
who have studied phosphatic sediments of the Aurora Embayment area
include Leutze (1968), Potlurl (1971), Katrosh (1981), Scarborough
(1981), Riggs and others (1982b), Katrosh and S.W. Snyder (1982),
Scarborough and others (1982), S.W.P. Snyder and others (1982),
Sledlécki (1984), and Allen (1985). Geochemical studies of Aurora Area
phosphate Include those by Ellington (1984), Dolfi (1983), Indorf
(1982), and Tobiassen (1982).
Riggs and others (1982b) recognized four cyclic sediment sequences
in the Pungo River Formation of the Aurora Area (Fig. 4). Siltciclastic
AVE.
FORMAnON AVC. % AVE. % % FHOS^TE % TERRCENOUS % CATOO^TE
THCxrcss
AM) UMT mosmATC CARBONATE 0 10 20 30 40 90 00 70 00 90 100M
UPPER
VOlWTOVW 19 0 30
LOWCR
3 to 3
YORKIOWN
2 90
0 2
9 at
c 2
••qu«Ac«
62 6
DIVER c 9 49 011 71 v.'.vvt ' . t Í1 ; I f-I-; 1 ; i 7 P-l}. i-¡ j
B 3
o 33 4 1
o 39 0
z
8 7
3
& 36 0
1 1 00 Î * ? f V ? * ? !
A 4
21 40 ^j i j i j iP
CÂ51ke 60
HAYNC 0 .• Í ; ; ll}.I î ‘j ; I j I j I j rt
• 0 «0 70 «0 so 40 30 20 10 0
Figure 4 . Average concentrations of phosphate, terrigenous
(siliciclastic), and carbonate sediments from
cores in the Aurora Area, N.C. (from Riggs and
others, 1982b).
9
components decrease upward within units A, B, and C. Phosphate
correspondingly increases upward within each unit, and then decreases
within the overlying carbonate sediments. Carbonate increases upward
gradually or through increasing interbeds and culminates in a
predominantly carbonate sediment. The carbonate sediment capping unit C
contains a diverse, warm temperate to subtropical, molluscan fauna (J.
Carter, pers. comm, to S.R. Riggs). An unconformity, separating each
carbonate from sillciclastic sediment of the overlying unit, is denoted
by an indurated carbonate surface containing a rock-boring infauna,
molds produced by dissolution of shells within the carbonate sediments,
and infilling of the extensive bore-hole system by overlying sediments.
Based on foramlnlfers and molluscs, Gibson (1967) suggested water
depths of 100 to 200 m for phosphate formation in units A, B, and C, and
70 to 100 m for associated carbonate cap rocks. Katrosh and S.W. Snyder
(1982) and S.W. Snyder and others (1982) state that units A and B
contain inner to middle shelf foraminiferal assemblages predominated by
Buliminella elegantisslma, a species that flourishes in areas with a
high nutrient supply. Riggs and others (1982b) and Riggs (1984) suggest
that the phosphorite sands of units A and B probably represent upwelllng
conditions, cold and somewhat toxic at the sediment-water interface.
More diverse species assemblages occur within the carbonate caps,
suggesting the restoration of more normal marine conditions during
deposition of carbonates (S.W. Snyder and others, 1982; Riggs and
others, 1982b).
Unit D contains a thin basal phosphatic sediment which rapidly
grades into a very fossillferous dolosilt containing abundant bryozoans
10
and barnacles. Scarborough and others (1982) traced unit D laterally
into a bryozoan-barnacle hash with less than 20% calcareous mud in the
central portion of the Aurora Embayment. Miller (1971) attributed this
facies change to secondary dolomitizatlon by movement of Mg-bearlng
groundwaters through an original micrite matrix. Rooney and Kerr (1967)
attributed dolomite in the Aurora Area to dolomitizatlon of limestones
by hypersaline brines, a process called seepage refluxion by Adams and
Rhodes (1960). Gibson (1967) stated unit D formed at depths of less
than 70 meters.
Units C and D contain benthic foraminiferal assemblages indicating
middle to outer shelf environments (Katrosh and S.W. Snyder, 1982).
Foramlnifers are more abundant and diverse than in units A and B, and
are Interpreted to represent a change from nutrient-rich to more normal
marine waters, a marine transgression, or a combination of the two
(Katrosh and S.W. Snyder, 1982).
Continental Shelf
Pilkey and co-workers first noted phosphate from surface sediments
in the central part of Onslow Bay (Pilkey and Luternauer, 1967;
Luternauer and Pilkey, 1967). Meisburger (1979), during a seismic and
vlbracore survey to locate beach replenishment sands on the inner
continental shelf of southern North Carolina, encountered Pungo River
sediments in two vibracores 11 km south of Bogue Banks in northern
Onslow Bay. Steele (1980) found phosphatlc sands underlying Pleistocene
barrier island sediments in the Bogue Banks area. Blackwelder and
others (1982) dredged middle Miocene moldic calcareous quartz sandstones
11
(similar to limestones which alternate with phosphorite sands in the
Aurora Area) in northern and central Onslow Bay. They also stated that
Miocene rocks dredged in northeastern Onslow Bay are among the youngest
rock units in the Pungo River Formation, and may be in part be early
late Miocene, correlative to the Eastover Formation in Virginia.
Five research cruises have been conducted by S.R. Riggs from May
1980 to May 1983. Vibracoring of seismic sequences defined by high
resolution profiling during these cruises has shown that Pungo River
sediments occur as far south as Frying Pan Shoals (Lewis, 1981; Lewis
and others, 1982; Snyder, S.W.P., 1982; Riggs and others, 1982a, 1985).
Waters (1983) and Waters and S.W. Snyder (in press) studied the abundant
foraminifers in southern Onslow Bay.
The Pungo River Formation in Onslow Bay consists of three
third-order seismic sequences, separated by regional unconformities
(S.W.P. Snyder, 1982; Snyder and others, 1982), deposited during
third-order coastal onlap cycles that are part of the Miocene
second-order supercycle (Fig. 5). Third-order sequences consist of more
numerous, fourth-order seismic sequences separated by local
unconformities (S.W.P. Snyder, 1982; S.W.P. Snyder and others, 1982).
Figure 1 shows the northeast-southwest subcrop pattern of 16 of these
sequences.
The oldest third-order seismic sequence is the FPF sequence of late
Burdigalian age (late early Miocene). It is composed of six
fourth-order seismic units labeled FPF-1 to FPF-6 from oldest to
youngest. In the Frying Pan Area, units FPF-1 and FPF-2 correlate with
planktonic foramlnlferal Zone N6, and unit FPF-6 with Zone N7 (Waters,
Figure 5 Chart showing the relationship of seismic sequences present in Onslow Bay
(modified from S«W.P. Snyder, 1982) to relative global sea-level (from Vail
and Mltchum, 1979).
13
1983). Steínmetz (in S.W.P. Snyder, 1982) assigned FPF-4 to calcareous
nanofossil Zone NN4. In seismic profile, FPF-1 through FPF-5 form a
series of low dipping units, while FPF-6 has the morphology of a large
channel (Fig. 6). This channel is filled with marine sediments (Waters,
1983) and has been Interpreted to be a product of erosion and deposition
by a spin-off eddy of the Gulf Stream.
The overlying third-order seismic sequence, which is Langhian
(early middle Miocene) in age, is referred to as the AF sequence. It
has been divided into four fourth-order seismic units, AF-1 to AF-4.
These units have been dated by Steinmetz as nannofossil Zones NN4-NN5
(in S.W.P. Snyder, 1982). Moore (in prep.) has assigned AF-3 to
planktonic foraminiferal Zone N9. Units C and D of the Pungo River
Formation in the Aurora Area appear to be correlative with the AF
seismic sequence in Onslow Bay (Katrosh and S.W. Snyder, 1982; Gibson,
1983). In seismic profile, the AF sequence thickens abruptly from 20 m
to 40+ m at the White Oak Lineament, where it forms a series of
progradlng clinoforms (Fig. 7).
The youngest third-order seismic sequence, the BBF sequence, is
Serravallian age (middle middle Miocene) on the basi$ of Steinmetz's
nanofossil date of Zone NN6 its the lower part (in S.W.P. Snyder, 1982).
Moore and S.W. Snyder (1985) assigned BBF sediments to planktonic
foraminiferal Zones N11-N14. This sequence is divided into six
fourth-order seismic units (BBF-1 to BBF-6) on Figure 1, but additional
seismic units have been recognized in the subsurface by S.W.P. Snyder
(1982). The BBF sequence displays complex patterns suggesting extensive
cut and fill of preceding units (see Fig. 10 in Riggs and others, 1985).
14
Figure 6. West-east interpreted seismic profile in the Frying
Pan Area of southern Onslow Bay (from Riggs and others,
1985). Location of this profile is shown in Figure 8.
15 M SECTION
1*0 *4*
• •4vti fM
«MiiMCOMI»
?»Mtoaa>4i|
*t*rw4i
•CMt
MIOCENE PUNQO RIVER EM ECONOMIC UNITS (PHOSPHORITES)
SEQUENCE BBF UNDIFFERENTIATED UNIT BBF-6
m SEQUENCE AF UNDIFFERENTIATED E13 UNIT BBF-1U
SEQUENCE FPF UNDIFFERENTIATED UNIT BBF-1L
FOR IDENTIFICATION OF THE REFLECTOR NOMENCLATURE SEE SNYDER (ISS2)
Figure 7. West-east Interpreted seismic profiles In northern Onslow Bay (from Riggs and
others, 1985). Location of these profiles Is shown In Figure 8.
16
Riggs (198A) hypothesized that the 17 or more fourth-order seismic
units were each characterized by some variation of an idealized vertical
sequence (siliciclastics, to phosphate and associated authigenic
sediments, to carbonates). Each cycle was deposited during
transgressions with a frequency between 100,000 and 1,000,000 years.
Regressions subsequent to the deposition of each unit may have resulted
in erosion and diagenetic alteration of all or part of each deposit,
with diagenesls decreasing down section (Riggs, 1984; Riggs and others,
1983, 1984).
Lewis (1981), in a preliminary study of the Pungo River Formation
in Onslow Bay, described three informal depositional sequences in
northern Onslow Bay: quartz sand, biorudite, and phosphatic sand. He
defined two lithofacies within the biorudite: barnacle biorudite and
bioclastic dolosllt. He also recognized five lithofacies in southern
Onslow Bay: phosphorite sand, quartz phosphorite sand, phosphorite
quartz sand, sandy mud, and mud. Table 1 summarizes the types and
percentages of carbonate Lewis found in the Pungo River Formation in
Onslow Bay. Allen (1985) analyzed eight dolomite samples from Onslow
Bay for carbon and oxygen isotopes. To date, no detailed descriptive
work has been done with Pungo River carbonate sediments recovered by
vibracoring in Onslow Bay
17
SEISMIC LEWIS' LEWIS' AVG. % DOMINANT DESCRIPTION OF
UNIT(S) UNIT FACIES FOSSILS FOSSILS CARBONATE MUD
bivalves
BBF 1-6 D Phosphatlc 5 barnacles minor silt-
Mud echinoids sized dolomite
foraminifers
AF-4 E Dry Bioclastic 22 barnacles dolosilt (74%)
Dolosilt
AF-4 E Barnacle 63 barnacles dolomite mud at base
Biorudite grading upward into
calcite mud (30%)
AF 1+2, F Quartz 13 barnacles 90% of silt is
FPF 1-6 Sand dolomite and clay
FPF-3 G Mud 9 foraminifers dolosilt to dolo-
silty clay (86%)
FPF-2 H Sandy Mud 15 foraminifers none described
FPF-1 I Phosphorite 23 foraminifers none described
Quartz Sand
FPF-1 J Quartz Phos- 5 foraminifers none described
phorite Sand
FPF-1 K Phosphorite 5 foraminifers none described
Sand
Table 1. Summary of the Pungo River carbonate sediments described by
Lewis (1981).
18
OBJECTIVES
The primary objective of this study is to describe the carbonate
petrology and sedimentology of the Fungo River Formation in Onslow Bay.
More specifically, sub-objectives are:
1) to describe the types of carbonate sediments, determine their
spatial distribution, and establish their relationship with
other mineral components (i.e., phosphate and slliciclastlc
sediments) within the formation;
2) to interpret the environment of deposition and diagenetic
history of the carbonate sediments; and
3) to test Riggs* (1984) model of cyclic sediment deposition
against observed vertical and lateral facies relationships of
the carbonate sediments.
19
METHODS OF INVESTIGATION
Sampling
Of 144 vlbracores (9 m maximum length) recovered in Onslow Bay
during research cruises from 1980 to 1983, 60 were used in this study
(Fig. 8). These cores were selected to provide the best possible
vertical and lateral coverage through each seismic unit. Table 2
summarizes the cores and samples studied.
Textural Analysis
For textural analysis, the Miocene portion of each core was sampled
approximately every 2.0 m or at changes in lithology, whichever came
first. One hundred forty-seven samples were dried, weighed, and wet
sieved through a 4.0 phi sieve (230 mesh). Mud was saved for insoluble
residue and x-ray diffraction analyses. The sand fraction was then
dried, weighed, and rotapped at a 0.5 phi Interval. Each 0.5 phi
fraction was weighed. Individual and cumulative weight percentiles were
calculated for each sample and are presented in Appendix D.
Reflected Light Microscopy
Each sample used for textural analysis was also examined for fossil
and mineralogical components using reflected light microscopy. Each 0.5
phi fraction was point counted (300 counts) to determine the volume % of
20
Figure 8 Map of Onslow Bay showing location of vibracores used in this
study and seismic profiles discussed in text.
50/5.75-6.00 FPF-5 X X X X 97/6.50-6.75 FPF-2 X X
50/8.25-8.50 FPF-5 X K X X 100/8.60-8.70 BBF-6 X X X
51/2.00-2.25 AF-l X X X X 102/7.00-7.25 FPF-6 X
51/5.00-5.25 AF-1 X X X 102/7.75-8.00 FPF-6 X
51/8.00-8.25 AF-l X X 108/1.75-2.00 BBF-3 X
52/3.75-6.00 BBF-1 X X X X 108/2.25-3.00 BBF-3 X
53/1.50-1.75 BBF-1 X X X 108/2.75-3.00 BBF-3 X X X
53/3.75-6.00 BBF-1 X X X X 108/3.75-6.00 BBF-3 X X X
53/5.50-5.75 BBF-l X 108/5.00-5.25 BBF-3 X X X X
53/5.90-6.00 BBF-1 X 109/1.50-1.75 BBP-1 X X X
53/6.00-6.25 BBF-1 X X X X 109/3.00-3.25 BBF-l X X X
58/2.25-2.50 AF-2 X X X X 109/6.50-6.75 BBF-1 X X X
58/6.25-6.50 AF-2 X X X X 109/5.75-6.00 BBF-1 X X X
58/6.25-6.50 AF-l X X X X 110/1.00-1.25 FPF-2 K X X
58/7.60-7.50 AF-l X 110/6.66-6.75 FPF-2 X X X
58/8.25-8.50 AF-l X X X X 111/0.25-0.50 AF-4 X
59/6.50-6.75 BBF-1 X X X X 111/0.50-0.75 AF-4 X X X
59/7.75-8.00 BBF-1 X X X X 111/2.50-2.75 AF-4 X X X
60/1.50-1.75 BBP-1 X X 111/6.10-6.20 AP-4 X
60/6.00-6.25 BBP-1 X X 111/6.25-6.50 AF-4 X X X
60/6.25-6.50 BBF-1 X X 111/6.75-5.51 AF-4 X
62/3.75-6.00 FPF-3 X X X X 111/5.50-5.75 AF-4 X X X
62/5.50-5.75 FPF-3 X X X X 111/6.25-6.50 AF-4 X X X
63/0.75-1.00 FPF-2 X X X X 111/7.50-7.75 AF-4 X X X
63/2.00-2.25 FPF-2 X X 111/8.00-8.25 AF-4 X X X
66/0.75-1.00 FPF-l X 113/0.50-0.75 FPF-l X X X
66/1.75-2.00 FPF-1 X 113/1.50-1.75 FPF-l X X X
66/2.75-3.00 FPF-l X 116/2.10-2.20 FPF-l X
66/3.50-3.73 FPF-1 X X 116/5.75-6.00 FPF-l X X X
66/5.75-6.00 FPF-l X X 116/7.50-7.75 FPF-1 X X X X
66/6.25-6.36 FPF-1 X 115/1.50-1.75 FPF-1 X
66/6.37 FPF-1 X 115/2.50-2.75 FPF-l X
67/3.50-3.75 FPF-6 X X X X 115/3.00-3.25 FPF-l X
67/6.50-6.75 FPF-6 X X 115/6.25-6.50 FPF-l X
70/1.50-1.75 FPF-2 X X X X 115/6.75-5.51 FPF-l X
71/0.50-0.75 BBF-l X X X X 115/5.00-5.25 FPF-l X X X
91/3.50-3.75 BBF-l X X X X 115/5.50-5.75 FPF-l X X X
91/5.50-5.75 BBF-1 X X X X 115/7.00-7.25 FPF-l X X X
92/3.25-3.50 BBF-2 X 123/2.00-2.25 FPF-2 X
92/3.50-3.75 BBF-2 X 123/6.65-6.55 FPF-2 X
92/6.00-6.25 BBF-2 X X X X 131/3.00-3.25 AF-3 X
92/5.50-5.75 BBF-2 X X X X 131/3.75-6.00 AF-3 X X X
96/1.00-1.25 BBF-l X 131/6.75-5.00 AF-3 X X X
96/1.50-2.00 BBF-1 X 131/5.75-6.00 AF-3 X X X
96/1.50-1.75 FPF-6 X X X X 131/6.36-6.66 AF-3 X
96/3.50-3.75 FPF-6 X X X X 136/0.25-0.50 FPF-1 X
96/5.50-5.75 FPF-6 X X X X
97/0.50-0.75 FPF-2 X X
97/2.50-2.75 FPF-2 X X
97/4.50-4.75 FPF-2 X X
Table 2 (continued) Summarization of sample analyses
50/5.75-6.00 rPF-5 X X X X 97/6.50-6.75 FPF-2 X X
50/8.25-8.50 FPF-5 X X X X 100/8.60-8.70 BBF-6 X X X X
51/2.00-2.25 AF-l X K X X 102/7.00-7.25 FPP-6 X
51/5.00-5.25 AF-l X X X 102/7.75-8.00 FPF-6 X
51/8.00-8.25 AF-1 X X 108/1.75-2.00 BBF-3 X
52/3.75-6.00 BBF-l X X X X 108/2.25-3.00 BBF-3 X
53/1.50-1.75 BBF-1 X X X 108/2.75-3.00 BBF-3 X X X X
53/3.75-6.00 BBF-1 X X X X 108/3.75-6.00 BBF-3 X X X X
53/5.50-5.75 BBF-1 X 108/5.00-5.25 BBF-3 X X X X X
53/5.90-6.00 BBF-1 X 109/1.50-1.75 BBF-l X X X X
53/6.00-6.25 BBF-1 X X X X 109/3.00-3.25 BBF-l X X X X
58/2.25-2.50 AF-2 X X X X 109/6.50-6.75 BBF-l X X X X
58/6.25-6.50 AF-2 X X X X 109/5.75-6.00 BBF-l X X X X
58/6.25-6.50 AF-l X X X X 110/1.00-1.25 FPF-2 X X X X
58/7.60-7.50 AF-1 X 110/4.64-4.73 FPF-2 X X X X
S8/8«2^8.50 AF-l X X X X 111/0.25-0.50 AF-4 X
59/6.50-6.75 BBF-l X X X X ill/0.50-0.75 AF-4 X X X X
59/7.75-8.00 BBF-l X X X X 111/2.50-2.75 AF-4 X X X X
60/1.50-1.75 BBF-l X X 111/6.10-6.20 AF-4 X
60/6.00-6.25 BBF-l X X 111/6.25-6.50 AF-4 X X X X
60/6.25-6.50 BBF-l X X 111/6.75-5.51 AF-4 X
62/3.75-6.00 FPF-3 X X X X 111/5.50-5.75 AF-4 X X X X
62/5.50-5.75 FPF-3 X X X X 111/6.25-6.50 AF-4 X X X X
63/0.75-1.00 FPF-2 X X X X 111/7.50-7.75 AF-4 X X X X
63/2.00-2.25 FPF-2 X X 111/8.00-8.25 AF-4 X X X X
66/0.75-1.00 FPF-1 X 113/0.50-0.75 FPF-l X X X X
66/1.75-2.00 FPF-1 X 113/1.50-1.75 FPF-l X X X X
66/2.75-3.00 FPF-1 X 116/2.10-2.20 FPF-l X
66/3.50-3.73 FPF-l X X 116/5.75-6.00 FPF-l X X X X
66/5.75-6.00 FPF-1 X X 116/7.50-7.75 FPF-l X X X X X
66/6.25-6.36 FPF-l X 115/1.50-1.75 FPF-l X
66/6.37 FPF-l X 115/2.50-2.75 FPF-l X
67/3.50-3.75 FPF-6 X X X X 115/3.00-3.25 FPF-1 X
67/6.50-6.75 FPP-6 X X 115/6.25-6.50 FPF-l X
70/1.50-1.75 FPF-2 X X X X 115/6.75-5.51 FPF-l X
71/0.50-0.75 BBF-l X X X X 115/5.00-5.25 FPF-l X X X X
91/3.50-3.75 BBF-l X X X X 115/5.50-5.75 FPF-l X X X X
91/5.50-5.75 BBF-l X X X X 115/7.00-7.25 FPF-l X X X X
92/3.25-3.50 BBF-2 X 123/2.00-2.25 FFF-2 X
92/3.50-3.75 BBF-2 X 123/6.65-6.55 FFF-2 X
92/6.00-6.25 BBF-2 X X X X 131/3.00-3.25 AF-3 X
92/5.50-5.75 BBF-2 X X X K 131/3.75-6.00 AF-3 X X X X
96/1.00-1.25 BBF-l X 131/6.75-5.00 AF-3 X X X X
96/1.50-2.00 BBF-l X 131/5.75-6.00 AF-3 X X X X
96/1.50-1.75 FPF-6 X X X X 131/6.36-6.66 AF-3 X
96/3.50-3.75 FPF-6 X X X X 136/0.25-0.50 FPF-l X
96/5.50-5.75 FPF-6 X X X X
97/0.50-0.75 FPF-2 X X
97/2.50-2.75 FPF-2 X X
97/6.50-6.75 FPF-2 X X
ro
ho
Table 2 (continued) Summarization of sample analyses
23
fossils and mineraloglcal components in that size range. The sample was
then described in terms of fossil preservation and authigenic
mineralization.
Percentages of each compositional element in the total sediment for
each sample were calculated by: 1) multiplying the % of each component
in each 0.5 phi fraction by the weight % of that phi fraction, and 2)
totaling these numbers for each sample. This data was generated using
SAS (Statistical Analysis System) and the results are presented in
Appendix A.
Insoluble Residue Analysis
The mud fraction of each sample saved during wet sieving was
divided into two splits. The split used for insoluble residue analysis
was first dried and weighed. Dilute hydrochloric acid (10% HCl) was
added to each sample until calcite was dissolved. Each sample was then
heated to 75°C to dissolve any remaining dolomite. Spent acid was
then decanted. Samples were washed in distilled water and filtered.
Filters with insoluble residues were dried in an oven at 50°C, after
which they were weighed. Percentages of insoluble residues and
carbonate in the mud fraction were calculated. These figures were then
recalculated in terms of the total sediment. Appendix B contains these
results.
24
X-ray Diffractoraetry
X-ray diffractoraetry was done on a GE-700 Diffractoraeter with
nickel filtered copper K-alpha radiation using standard x-ray
techniques. Three types of saraples were x-rayed: bulk raud fraction to
determine the presence or absence of calcite and dolomite, dolomite
concentrates, and chert nodules.
The second split of the mud fraction was used to determine the
presence or absence of calcite and dolomite in the mud fraction.
However, calcite or dolomite must constitute approximately 5% or more of
the sample to produce peaks on diffractograms. Appendix B shows the
results of this study.
Dolomite concentrates were x-rayed at 1°20 per minute to
accurately determine dolomite peak postions. Chert nodules were x-rayed
to determine the variety of silica present in the nodules. The results
of these two studies are discussed in the sections on dolomite and
silicification, respectively.
Thin Section Analysis
Forty-six thin sections were prepared from indurated and
semi-indurated Pungo River sediments to study diagenetic features not
observable in the unconsolidated sediments. Semi-indurated sediments
were impregnated with Hillquist epoxy to prevent plucking of grains
while grinding and polishing. Thirteen non-lithified sediment samples
were commercially vacuum impregnated to observe structures and features
25
were commercially vacuum Impregnated to observe structures and features
not observable in reflected light microscopy. Cover glasses were not
affflxed to thin sections to permit later x-ray diffractometry.
Each thin section was stained for calcite, dolomite, and ferroan
dolomite according to the procedure of Katz and Friedman (1965). This
procedure stains calcite red, dolomite blue, and ferroan dolomite does
not stain. Each section was then point counted (300 counts) to
determine mineralogy and fossil content. These results are recorded in
Appendix C.
Scanning Electron Microscopy
Portions of chert nodules, selected dolomite rhombs, and fossils
were examined with an ISI-40 Scanning Electron Microscope to observe
surface textures of diagenetic features.
26
PETROLOGY
Both reflected light and petrographic microscopy were used to
identify constituents of the Pungo River Formation in Onslow Bay. Table
3 summarizes the average abundance and Table 4 summarizes the range of
abundances of the fossil and mineral constituents in each seismic unit.
Unless otherwise stated, all abundances are expressed as percentages of
the total sediment. Tables 3 and 4 are based on point counts of
sediment by reflected light microscopy (Appendix A). Constituents are
individually discussed below.
Deposltional Components
Carbonate Allochems
Carbonate allochems in the Pungo River Formation include fossils,
ooids, superficial ooids, and pelolds. Oolds, superficial ooids, and
peloids are rare. Fossils constitute up to 82% of the total sediment.
Calcareous fossils are diverse in the Pungo River Formation (Table 3);
however, only barnacles, molluscs, foramlnifers, and echlnoids are
common. Many authors (Horowitz and Potter, 1971; Milliman, 1974;
Bathurst, 1975; Scholle, 1978; Flugel, 1982) have published descriptions
and thin section photomicrographs of the ultrastructure of the common
fossils; therefore, they need not be repeated here.
Arthropods. Barnacles, the most abundant allochems in most Pungo
River sediments (Table 3), compose up to 70.3% of the sediment (Appendix
Seismic # of
Unit Samp Moll Barn Bry Ech Ost Bf Pf Garb Spar Dolo Cher Dlat Rads Splc Skel Phos Glau Opaq 0th Qtz Matr
BBF-6 6 0.1 tr 0 0.4 0 1.2 0 0.3 tr 1.0 0 0 0 0 2.8 6.6 0.1 tr tr 62.0 25.5
BBF-3 3 0.5 11.5 0.1 0.7 tr 1.6 0.1 3.0 5.0 0 0 0 0 0 0.2 tr tr 0 0 19.9 57.4
BBF-2 2 0.2 tr 0 0.1 0 tr 0 0.6 0.4 0 0 0 0 0 tr tr 0 tr 0 88.7 10.0
BBF-I 27 0.4 0.9 tr 0.2 tr 0.4 tr 0.3 0.2 0.1 0 tr 0 0 1.9 5.0 0.2 tr tr 48.6 41,5
AF-4 14 9.3 32.4 4.6 0.8 tr 0.6 0.1 5.6 4.6 0.2 0 0 0 tr tr O.l 0 tr 0.1 1.2 40.4
AF-3 5 6.5 13.2 1.1 4.5 0.1 1.0 0.2 8.3 4.1 tr 0 0 0 0 tr 0.3 tr 0.1 0 28.8 31.8
AF-2 4 1.4 15.8 0.1 1.1 0 3.6 1.3 4.4 5.9 0 0 0 0 0 0.2 0.3 0.1 0 0 32.4 33.5
AF-1 20 0.9 1.7 0.1 1.2 0.2 0.9 0.1 2.4 0.8 tr tr 0.2 tr tr 0.2 0.6 tr tr tr 49.4 41.1
FPF-6 9 1.0 5.1 0.2 6.9 tr 5.5 3.5 5.9 1.2 tr 0 0 0 0 0.7 0.6 tr tr 0 39.9 29.6
FPF-5 7 2.1 6.3 0.2 2.0 tr 0.7 0.2 3.7 0.9 tr 0 0.1 0 tr 0.3 0.3 tr tr 0 42.6 40.5
FPF-4 3 19.8 3.0 0 0.1 tr 0.1 0 0.3 tr 0 0 0 0 0 0.5 tr tr 0 0 65.6 10.4
FPF-3 7 0.1 0.3 tr 0.5 tr 1.6 0.1 1.2 1.4 tr 0.2 tr 0.1 tr 0.2 0.5 tr 0-2 tr 32.4 61.0
FPF-2 24 O.l tr tr 0.1 tr 1.9 0.9 0.3 0.3 tr 0.2 0.2 tr tr 0.7 l.l tr tr 0.2 26.0 67.9
FPF-l 16 0.3 2.1 0.5 0.4 tr 12.1 3.0 1.0 0.4 0.1 tr 0 0 0 3.2 13.8 0 tr 0 23.4 39.8
Table 3» Average conposltion (tn X of the total sedinent) of aanples studied froa each Pungo River seismic sequence tn
Onslow Bay* (Noll * molluscs; Barn ?? barnacles; Bry ? bryozoans; Ech * ebhinolds; Ost * ostracods; Bf ?
benthic foramlnlfers; Pf • planktonic foramlnlfers; Garb » unidentifiable carbonate fragments; Spar caldee
cement; Dolo " dolomite; Cher ? chert; DIat* diatoms; Rads • radlolarians; Splc * spicules; Skel - skeletal
phosphate; Phos *? nonskeletal phosphate; Glau - glauconite; Opaq - opaques; 0th - others; Qtz • sllfdclastic
sand; Matr « matrix.)
Seisnic f ot
Unit Samp Moll Barn Bry Ech Ost Bf Pf Garb Spar Dolo Cher Diat Rads Spic Skel Phos Glau Opaq 0th Qtz Matr
BBF-6 b Ü 0 0 tr 0 tr 0 tr 0 0.2 0 0 0 0 0.1 tr 0 0 0 53.5 17.5
0.3 tr 0 1.6 0 3.7 0 0.6 0.1 2.4 0 0 0 0 4.7 10.5 0.2 tr 0.4 67.0 44.4
BBF-3 3 0.3 6.6 0.1 0.4 0 1.3 0 l.B tr 0 0 0 0 0 tr tr 0 0 0 10.9 39.5
0.7 18.7 0.2 1.0 0.1 1.7 0.2 5.0 9.3 0 0 0 0 0 0.3 tr tr 0 0 27.6 77.8
BBF-2 2 0.1 0 0 0.1 0 tr 0 0 0 0 0 0 0 0 tr tr 0 0 0 83.9 6.0
0.4 tr 0 0.1 0 tr 0 1.2 0.8 0 0 0 0 0 tr tr 0 tr 0 93.4 13.9
BBF-1 27 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.1 tr 0 0 0 6.1 19.2
3.8 15.3 0.2 2.6 0.2 4.9 0.1 6.0 2.9 0.8 0 0.1 0 0 6.4 22.2 1.6 tr 0.3 71.6 92.2
AF-4 14 0 4.3 0 0 0 tr 0 1.3 0 0 0 0 0 0 tr tr 0 tr tr 0.1 18.3
20.6 65.6 12.4 3.8 0.4 2.1 0.5 10.5 38,2 1,7 0 0 0 tr tr 0.3 0 0.1 1.1 4.1 60.1
AF-3 5 0.4 3.0 0.5 2.4 0 0.2 O.l 3.2 0 0 0 0 0 0 0 0 0 0 0 14.3 26.8
10.9 26.9 1.6 6.9 0.4 2.1 0.7 11.1 7.9 tr 0 0 0 0 tr 0.7 tr 0.2 0 36.7 36.5
AF-2 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 tr 0 0 0 0 2.7 4.8
4.0 41.9 0.4 2.2 0 12.5 4.6 13.3 22.4 0 0 0 0 0 0.5 0.6 0.3 0 0 94.5 97.3
AF-1 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.5 2.8
7.1 18.9 0.9 1.8 3.4 11.0 1.0 10.8 7.9 0.5 0.8 2.S tr tr l.O 3.1 tr tr 0.2 94.8 97.2
FPF-6 9 0 0 0 1.6 0 0.4 0.1 0 0 0 0 0 0 0 0 0 0 0 0 8.7 12.6
4.4 27.5 0.8 13.6 0.2 10.4 13.7 22.8 6.9 0.2 0 0 0 0 l.l 1.1 tr tr 0 68.9 49.9
FPF-5 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 tr 0 0 0 3.6 11.6
8.3 31.6 1.0 6.9 0.1 2.6 0.6 14.8 4.4 0.2 0 0.5 0 tr 1.4 0.8 tr 0.2 0 88.0 95.8
FPF-4 3 0.3 tr 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0 0 0 0 38.8 10.2
46.2 4,8 0 0.2 tr 0-2 0 0.9 tr 0 0 0 0 0 0.9 tr 0.1 0 0 88.1 10.7
FPF-3 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 tr tr 0 0 0 0.5 10.4
0.6 1.5 O.l 1.7 0.1 6.4 0.4 5.6 10.0 tr 1.5 0.1 0.2 o.l 0.9 1.6 tr l.l 0.1 78.6 99.2
FPF-2 24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 tr 0 0 0 0 tr 8.8
1.2 0.1 0.2 0.5 tr 19.1 0.9 2.9 6.3 0.3 5.1 2.4 0.2 0.3 3.2 9.1 0.2 tr 3.2 66.3 99.9
FPF-1 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.0 1.3 0 0 0 7.3 19.1
2.7 25.4 4.7 2.8 0.1 29.7 7.2 4.3 5.3 1.0 tr 0 0 0 6.9 36.9 0 tr 0 61.7 64.7
Table 4. Range (n composition (in X of the total sediment) of samples studied from each Fungo River seismic sequence in
Onslow Bay* The upper number for each seismic sequence represents the minimum value and the lower number
represents the máximum value. See Table 3 for abbreviations of components.
29
C). They are disarticulated in all but one sample. Barnacle plates
have characteristic shapes and a hollow appearance due to the presence
of longitudinal tubes and ribs. Compartmental plates are concave,
whereas opercular plates are triangular (Plates 1 and 2). Plates are
easily recognized petrographically by their grainy, microcrystalline
texture and numerous longitudinal tubes (Plates 3 and 4). Large
fragments of barnacle plates are usually poorly laminated in thin
section; thus, smaller fragments may be totally nonlaminated. Barnacles
may be mlsidentified as molluscs in thin section because of their
laminations (Mllliman, 1974). Molluscs, however, usually have well
defined laminations within a two-layer shell. Barnacles may also be
mlsidentlfled as bryozoans because longitudinal and transverse sections
through barnacle plates often look similar to zooecla in bryozoan
fronds. The principal distinguishing aspect is the fibrous
ultrastructure of bryozoans compared to the grainy ultrastructure of
barnacles.
Ostracods occur in trace amounts throughout most Pungo River
sediments (Table 3). They are most abundant in core OB-35 at 7.75-8.00
m where they constitute 3.4% of the total sediment (Table 4). Both
smooth shelled and highly ornamented forms are found, but smooth shelled
varieties are most abundant (Plate 5).
Portions of crab claws (decapods) are often present as trace
constituents in barnacle hashes but are generally absent elsewhere.
They are found in seismic units FPF-1, AF-3, AF-4, BBF-1, and BBF-3
(cores OB-33, OB-71, OB-108, OB-111, OB-115, and OB-131). Plate 4 shows
a cross section through a crab claw.
30
Plate 1. FPF-1 washed sediment. Opercular (0) and compartmental (C)
barnacle plates and echlnoid (E) plate with partial syntaxlal
cement overgrowth. Core OB-45, 1.00-1.25m. (reflected
light, 12x)
Plate 2. FPF-1 washed sediment. Barnacles (B), bryozoans (Z),
echlnoid spines (E), foramlnlfers (F), and fish bones (P) are
present. Core OB-115, 5.00-5.25m. (reflected light, 12x)
31
Plate 3. Barnacle plates. Notice the isopachous cernent lining the
Intraparticle pores in the plates. Microspar is also present
at the bottom center of the photograph. Core OB-33,
2.50-2.75m. (crossed niçois, 25x)
Plate 4. Carbonate cap rock on FPF—1 showing benthic foramlnifers (F),
barnacle (B), dasycladacean algae (A), crustacean (C),
bryozoan (Z), pelletai phosphate (P), Intraclastic phosphate
(I), and isopachous cement coating most of the fossils. The
clear area between allochems Is epoxy. Core OB-115,
2.50-2.75m. (transmitted light, 25x)
32
Plate 5. Washed sediment of AF-1. Ostracods (0), bivalves (B), and
echinoids (E) are shown. The echinoid has a thick syntaxial
cement overgrowth (E). Core OB-35, 5.25-5.00m. (reflected
light, 12x)
Plate 6. Washed sediment of FPF—6. Abundant planktonic foraminifers
(PF), benthic foraminifers (BF), and echinoid spines (E) are
illustrated. Core OB-96, 3.50-3.75m. (reflected light, 12x)
33
Molluscs. Most samples throughout each Pungo River seismic sequence
contain bivalve shell fragments (Plate 5). They range in abundance from
0% to 46.2% of the total sediment (Table 4). The AF sequence generally
contains more bivalve fragments than either the BBF or FPF sequences
(Table 3).
Gastropods are rare to absent in all but one core (OB-131) where
they constitute up to 1.4% of the total sediment. They have been
Included with bivalves for statistical purposes.
Echinoderms. Echlnoderms are represented by fragmented echinold
spines and plates (Plates 1, 2, 5, and 6). Though present in all
seismic sequences, they are most abundant in seismic unit FPF-6 where
they compose up to 13.6% of the total sediment (Appendix C). Average
abundances range from 0.1% to 6.9% of the total sediment (Table 3).
Preservation of echinoids ranges from perfectly preserved, through
all stages of syntaxial cement overgrowths, to the total encasement of
fine sand-sized echinoid fragments by syntaxial cement that forms doubly
terminated calcite crystals. Echinoid preservation is discussed in more
detail in the diagenesis section.
Foraminlfers. Benthic and planktonic foraminifers are present in most
Pungo River seismic units (Plates 4 and 6). Average abundance of
benthic foraminifers ranges from less than 1% to 12.1% of the total
sediment, while planktonic foraminfers range from 0% to 5.5%.
Preservation of foraminifers varies within each seismic séquence.
34
This will be discussed in more detail in the lithologic descriptions of
each seismic sequence.
Bryozoans. Bryozoans occur frequently and compose an average of up to
4.7% of the total sediment. They are generally more abundant where
barnacles are abundant; elsewhere, they are rare to absent (Table 3).
Bryozoans are represented by fragments of branching, encrusting, and
beehive-shaped forms (Plate 2).
Algae. Dasycladacean algae were noted in thin section as trace
constituents only in the carbonate-rich part of seismic unit FPF-1
(Plate 4). Coralline red algae (Plate 7) were seen as trace
constituents in seismic units FPF-1, FPF-2, AF-3, and AF-4 (cores OB-63,
OB-111, OB-114, OB-115, and OB-131).
Brachiopods. Three recrystallized terebratulld brachlopods were found
in seismic unit FPF-1 in the southernmost part of Onslow Bay (core
OB-114, 7.50-7.75 m). They were most likely eroded from older
sediments, probably from the Castle Hayne Formation (Eocene) where they
are common. Evidence for reworking is the highly recrystallized nature
of these shells in a sediment containing well preserved planktonic
foraminifers, which are among the first organisms to be diagenetically
altered.
Coated grains. Ooids are rare to absent throughout the Pungo River
Formation. They were seen in thin section only in seismic unit FPF-1,
35
Plate 7. Coralline red algae. Core OB-115, 2.50-2.75m.
(crossed niçois, 25x)
36
in core OB-64 at 2.75 m below sediment surface where they compose less
than 1% of the sediment. Superficial ooids are calcite coated, medium
to coarse sand-sized, quartz grains and are usually a pale gray color.
They are found in central Onslow Bay in seismic sequences FPF-2, FPF-3,
FPF-5, and AF-1, but they never exceed 1% in abundance.
Peloids are present in abundances of less than 4% as determined in
thin section. They are only present where barnacles are abundant and
their microstructure is grainy like that of the barnacles. This
suggests most of that the peloids are small, rounded, unlaminated
fragments of barnacles.
Others. Point counts of sieved samples becomes more difficult with
decreasing grain size. Poor preservation and/or transportation may
destroy shell microstructure and surface texture so that many grains
cannot be identified. These make up the majority of unidentifiable
carbonate grains. Coralline red algae, dasycladacean algae, crab claws,
terebratulid brachiopods, coated grains, and peloids are all present in
such small amounts that they were Included with unidentifiable carbonate
grains for statistical purposes.
Siliceous Allochems
Several types of siliceous organisms are present in the Pungo River
Formation. Diatoms (Plate 8) are most abundant (Table 3); sand-sized
specimens constitute up to 2.5% of the total sediment (Table 4).
Reported diatom concentrations are probably lower than true abundances
because most species are smaller than 63 microns. Diatoraaceous muds
37
Plate 8. Washed sediment of AF-1. Notice the abundant diatoms (D) and
siliceous sponge spicules (S). Also present are mollusc
fragments, benthic foraminifers, and ostracods. Core OB-34,
6.00-6.25m. (reflected light, 12x)
Plate 9. Diatomaceous mud. Core OB-17, 3.00-3.25m. (transmitted
light, 160x)
38
were Ideatlfled in thin section (Plate 9) in cores OB-17 and OB-47.
Radiolarians and siliceous sponge spicules occur in association with
diatoms (Table 3). Both monaxon and branching siliceous spicules are
found with monaxon varieties being the most abundant (Plate 8).
Siliceous organisms are generally associated with fine grained,
dominantly siliciclastic sediments. An exception is in core OB-34
(seismic unit AF-1) where the greatest diversity of siliceous and
carbonate secreting organisms is found.
Phosphate Allochems
Phosphate allochems were separated into skeletal and nonskeletal
varieties to determine their abundances. Skeletal phosphate occurs as
fish bones (Plate 2) and teeth, small sharks teeth, and fragments of the
inarticulate brachiopod Lingula. Due to its relative scarcity,
brachlopod material was included with vertebrate material as the
skeletal phosphate component for statistical purposes. Skeletal
phosphate content ranges from 0% to 6.9% of the total sediment. It is
most abundant in seismic units FPF-1, BBF-1, and BBF-6. Elsewhere,
average skeletal phosphate content is less than 1% (Table 3).
Intraclastlc and pelletai phosphate grains (Plate 4) were combined
as the nonskeletal phosphate component. No attempt was made to
determine the individual percentages of these grain types. Nonskeletal
phosphate content in ranges between 0% and 36.9% of the total sediment
(Table 4). Phosphate is most abundant in seismic units FPF-1, BBF-1,
and BBF-6. In the other seismic units, average phosphate content is
less than 2% (Table 3).
39
Glauconite
Glauconite is present as a trace constituent in both sieved samples
and thin section (Table 3). Identified by its bright to dark green
color, round to subangular grains occur in the coarse silt to fine sand
size fraction.
Siliciclastic Sands
Quartz is the most abundant type of siliciclastic sand present in
the Pungo River Formation of Onslow Bay. Minor amounts of muscovite,
plagioclase feldspar, microcline, and accessory minerals are combined
with quartz as the siliciclastic component for statistical purposes.
Matrix
Matrix, as used here, encompasses all materials finer.than 63
microns and Includes micrite, microspar, clay minerals, clinoptllolite
laths, silt-sized quartz, and most diatoms and dolomite present in the
Pungo River Formation. Clinoptllolite and dolomite are discussed in the
dlagenesis section. Micrite is very rare In thin section; most of the
carbonate mud is in the size range of microspar and is discussed in the
diagenesis section. Lyle (1984) identified the following clay minerals
in the Pungo River Formation in Onslow Bay: montmorlllonite, illite,
chamosite, and sepiolite.
Diagenetlc Components
Introduction
Dlagenesis refers to all chemical, physical, and biological changes
which take place in sediments after their initial deposition excluding
metamorphism. It includes such diverse processes as compaction,
micrltizatlon, cementation, mineral transformations, recrystallization,
dissolution, authigenic mineralization, grain to grain pressure
solution, stylolitization, and annealing of fractures. The type and
extent of dlagenesis is controlled by a variety of factors including
composition, porosity, and permeability of the sediments, composition of
the pore waters, time, temperature, and pressure. Because these factors
are so complex, many aspects of diagenesis are poorly understood. The
terms early and late dlagenesis, rather vague phrases used to describe
the relative timing of diagenetlc events, are related more to changes in
pore water composition and burial depth than to actual time.
Diagenetlc components within the Pungo River Formation Include
calcite cements, dolomite, authigenic silica, and zeolites. Calclte
cements, dolomite, and authigenic silica are described from thin
section. Zeolites are described only from reflected light microscopy.
Table 5 shows the relative abundance of diagenetlc components described
from thin sections (summarized from Appendix C), which were mostly from
carbonates due to the focus of this thesis. Relative timing of
dlagenesis is discussed in each section on diagenetlc components.
Saaple Area Spar Nier Hatr Dolo Cher Chai Foss 0th Otz Saaple Area Spar Hier Hatr Dolo Cher Chai Foss 0th Qtz
BBF-3 AF-1
108-1.75 22a 6.0 46.0 0.0 0.0 0.0 0.0 15.3 0.3 32.3 35-8.00 t5B 0.0 0.0 0.0 7.0 66.0 7.7 9.0 0.3 10.0
108-2.25 22a 1.3 45.7 0.0 0.0 0.0 0.0 26.3 0.0 26.7 38-7.25 22a 0.0 0.0 0.0 0.0 99.3 0.7 0.0 0.0 0.0
108-5.00 22a 0.0 58.1 0.0 0.0 0.0 0.0 12.9 0.0 29.1 44-5.90 22a 0.0 0,0 0.0 0.0 99.0 0.7 0.0 0.0 0.3
BBF-2 FPF-6
92-3.25 1-4 20.5 20.9 0.0 0.0 0.0 0.0 4.3 3.6 50.8 102-7.00 FP 11.7 0.0 4.0 0.0 0.0 0.0 72.7 0.7 10.9
92-3.50 1-4 18.4 10.0 0.0 0.0 0.0 0.0 1.2 2.8 67.7 102-7.75 FP 24.0 1.0 8.0 0.0 0.0 0.0 57.1 0.9 9.3
BBF-l FPF-3
94-1.00 1-4 8.3 72.0 0.0 0.0 0.0 0.0 3.3 4.0 12.3 17-3.00 FP 0.0 0.0 6A.7 17.3 0.0 0.0 8.0 2.4 7.7
94-1.50 1-4 11.1 63.0 0.0 0.0 0.0 0.0 0.0 5.9 20.0
53-1.50 1-4 0.0 73.7 0.0 0.0 0.0 0.0 2.7 5.3 18.3 FPF-2
53-5.50 1-4 0.7 58.3 0.0 0.0 0.0 0.0 2.7 10.7 27.7 47-0.00 1-4 0.0 0.0 55.4 12.9 0.0 0.0 0.0 8.9 22.7
53-5.90 1-4 6.7 81.3 0.0 0.0 0.0 0.0 0.0 3.3 8.7 47-7.25 1-4 0.0 0.0 80.9 0.0 0.0 0.0 0.0 2.6 16.4
123-2.00 — 0.0 0.0 0.0 11.7 63.0 0.0 0.0 0.0 25.3
AF-4 123-5.07 — 0.0 0.0 0.0 4.5 27.5 0.5 0.0 5.0 62.5
3-8.75 15a 0.0 48.3 0.0 0.0 0.0 0.0 51.3 0.0 0.0 123-6.74 — 0.0 0.0 0.0 15.2 36.4 0.8 0.0 3.2 44.4
33-2.50 15a 0.4 18.0 0.0 0.0 0.0 0.0 80.6 0.0 0.0 29B-2.75 FP 0.0 0.0 29.3 0.0 0.0 0.0 24.3 6.7 36.4
33-3.25 15a 0.0 16.3 0.0 4.0 0.0 0.0 78.3 0.0 1.3 29B-6.75 FP 0.0 0.0 46.0 0.0 0.0 0.0 16.3 17.7 20.0
33-4.00 15b 0.0 32.6 0.0 11.7 0.0 0.0 54.8 0.0 1.0
33-5.25 15a 0.0 39.6 0.0 0.0 0.0 0.0 55.6 0.0 4.7 FPF-1
33-6.40 15a 0.0 0.0 50.3 4.7 0.0 0.0 40.2 1.2 3.5 134-0.00 22a 7.1 47.2 0.0 0.0 0.0 0.0 8.4 1.3 35.9
33-8.00 15a 0.0 55.0 0.0 0.3 0.0 0.0 40.0 2.0 2.7 14-3.75 FP 0.0 0.0 38.7 0.3 0.0 0.0 8.7 30.3 22.0
111-0.25 15b 0.0 53.0 0.0 0.0 0.0 0.0 43.0 1.0 3.0 20-0.50 FP 4.0 43.6 0.0 1.4 0.0 0.0 41.3 4.0 5.7
Ul-4.10 15a 0.0 68.0 0.0 0.0 0.0 0.0 27.7 0.3 4.0 24-1.25 FP 0.0 0.0 26.3 0.0 0.0 0.0 1.0 68.4 4.3
111-4.75 15a 0.3 45.0 0.0 0.0 0.0 0.0 51.9 0.0 2.7 24-1.67 FP 0.0 27.7 0.0 0.0 0.0 0.0 1.0 45.3 26.0
64-0.75 FP 1.3 43.6 0.0 0.0 0.0 0.0 42.0 2.5 10.5
AF-3 64-1.75 FP 0.3 50.2 0.0 0.0 0.0 0.0 40.9 1.5 7.1
34-2.00 15b 2.7 41.3 0.0 0.0 0.0 0.0 22.4 0.7 24.0 64-2.75 FP 0.0 68.8 0.0 0.0 0.0 0.3 20.6 2.1 8.2
131-3.00 1-5 0.0 76.0 0.0 0.0 0.0 0.0 16.7 1.0 6.3 64-6.00 FP 4.7 52.1 0.0 0.0 0.0 1.3 16.2 0.0 25.4
131-6.34 1-5 5.3 55.8 0.0 0.0 0.0 0.0 28.2 1.0 9.7 64-6.25 FP 0.0 32.8 0.0 0.0 0.0 0.3 27.2 0.6 39.1
64-6.37 FP 1.7 79.2 0.0 0.0 0.0 0.0 1.2 0.0 17.9
AF-2 114-2.10 FP 2.3 56.3 0.0 0.0 0.0 0.0 38.0 0.0 3.3
38-0.50 22a 0.0 3.0 0.0 0.3 0.0 0.0 79.0 6.3 11.3 114-7.75 FP 0.7 62.2 0.0 0.0 0.0 0.0 7.0 0.6 29.4
58-7.40 1-5 0.0 0.0 0.0 0.0 0.0 32.7 0.0 1.3 65.9 115-1.50 FP 1.3 36.8 0.0 0.0 0.0 0.0 59.5 0.9 1.6
115-2.50 FP 1.1 45.4 0.0 0.0 0.0 0.0 44.5 2.8 6.2
AF-1 115-3.00 FP 1.5 44.3 0.0 0.0 0.0 0.0 43.3 5.9 5.3
35-4.10 15b 0.0 0.0 0.0 5.3 58.9 13.7 7.9 1.3 12.8 115-4.25 FP 2.8 34.8 0.0 0.0 0.0 0.0 45.6 8.8 8.2
35-6.75 15b 0.0 61.7 0.0 6.3 0.0 0.0 16.6 0.3 14.0 115-A.75 FP 1.7 36.4 0.0 0.0 0.0 0.0 39.9 8.4 13.2
35-7.25 15a 0.0 0.0 0.0 4.7 68.7 2.7 12.7 0.0 11.3
Table SuMartzation of thin section point counts to show abundances of diagenetlc coaponents (froa Appendix C)«
Coaponents are shown In X of total sedlaent* (Saaple > core-^top depth of saaple; Area - seisalc profile or
Frying Pan (FP) Area; Spar ? calcfte ceaent; Hier • alcrospar; Matr * aatrlx; Dolo - doloalte; Cher •
alcrocrystalllne quartz; Chai - chalcedony; Foss - fossils; 0th •• phosphate, glauconite, and pyrite; Qtz -
si liciclastic sand*)
42
Calcite cements
Calcite cements are classified on the basis of crystal morphology,
size, and orientation. The following varieties of calcite cement are
found in Pungo River sediments in Onslow Bay: radial rim cements,
syntaxial cement, pore filling cement, and microspar. Radial rim
cements, syntaxial cement, and pore filling cement are combined in point
count data as the sparry calcite cement component. The following
discussion of calcite cements is based on thin section descriptions of
crystal morphology, without support from any microprobe data.
Radial Rim Cements. Radial rim cements are those in which calcite
crystals radiate into existing pore spaces. The original mineralogy of
these cements may have been aragonite, high-Mg calcite, or low-Mg
calcite; however, they are now entirely low-Mg calcite, as determined by
staining techniques.
Isopachous and prismatic radial rim cements occur in the Pungo
River Formation. The predominant type is isopachous cement. In the
Pungo River Formation radial rim cements coat carbonate grain surfaces
almost exclusively; however, echinoid fragments are never covered by
radial rim cements.
Isopachous rim cement is a thin (15-30um) rind of roughly uniform
length calcite crystals which are oriented normal to the host grain
surface (Plates 4 and 10). Isopachous cement is a first generation
cement which lines interparticle and intraparticle primary pore spaces.
Crystal shape may be bladed, prismatic, equant, or fibrous. The
dominant crystal forms are bladed and prismatic. Fibrous isopachous
43
Plate 10. Isopachous rim cement (prismatic crystal shape) on a
planktonic foraminifer. Core OB-102, 7.00-7.25m. (crossed
niçois, 160x)
44
cement rarely occurs as intraparticle cement lining tubes in barnacle
plates.
Prismatic rim cement, also called dog-tooth cement (Flugel, 1982),
does not have a uniform crystal length and is usually larger than
isopachous cement, up to about 60um long. Prismatic cement is found
both as a first generation cement lining interparticle and intraparticle
primary pore spaces and as a second generation cement lining secondary
moldic pore spaces.
Isopachous cement is usually considered to be indicative of early
marine diagenesls (Longman, 1980). Prismatic cement is usually
Indicative of fresh water phreatic diagenesls, but has been found in
beach rocks and marine sediments (Longman, 1980; Flugel, 1982). Where
prismatic cement is found with isopachous cement lining primary pore
space in the Pungo River Formation it probably is of marine origin.
Where prismatic cement is found lining moldic secondary pore space it is
associated with blocky calcite cement and is most likely of fresh water
phreatic origin.
Syntaxial Cement. Syntaxial cement is a sparry calcite rim cement
which forms in optical and crystallographic continuity with host grains.
It commonly surrounds echlnoderm fragments; however, it has been- found
on corals, molluscs, and foramlnlfers (Burgess, 1979). Echlnoderm
plates and spines are either single crystals of calcite or are composed
of numerous minute crystals all with the same orientation (Towe, 1967).
The c-axls in echinold fragments is parallel to the length of spines and
is generally normal to plate surfaces (Bathurst, 1971). Growth of
syntaxlal cement Is much faster along the c-axis than in any other
direction (Evamy and Shearman, 1965, 1969).
Syntaxlal cement is common in Pungo River sediments and usually
surrounds echinoid fragments (Plate 11). It is volumetrically most
abundant in echlnold-foramlniferal biosparites of seismic unit FPF-6
where it composes approximately 18% of the total sediment.
Because much of the Pungo River Formation is unlndurated, the
sequential development of syntaxlal cements can be easily studied with
scanning electron microscopy. Plate 12 shows a fragment of a well
preserved echinoid plate. Early growth of syntaxlal cement begins as
many small calcite crystals form along the top surface of an echinoid
plate (Plate 13); canals in the echinoid plate are not infilled.
Further growth of the cement consolidates many small crystals into a few
large calcite crystals, accompanied by partial infilling of canals.
Porosity of the echinoid fragment is still relatively high at this point
(Plate 14). As cement continues to be added, surfaces parallel to the
plate are encased in a thick layer of calcite while surfaces normal to
the plate are encased in a thin layer (Plate 5).
Syntaxlal cement generally is believed to precipitate in fresh
water phreatic environments (Land, 1970; Longman, 1980). It may also be
an early marine cement, as evidenced by marine borings in the cement
(Burgress, 1979); however, evidence for a marine origin is not present
in the Pungo River Formation.
Pore Filling Cements. Pore filling cement is second generation sparry
calcite which occludes primary Interparticle and secondary moldic
46
Plate 11. Syntaxial cement overgrowths (S) on echinoid fragments (E).
Chambered fossils are foraminifers. Core OB-102,
7.00-7.25m. (crossed niçois, 25x)
Plate 12. Well preserved echinoid plate fragment. The right side is
150x magnification; the left side is a lOx magnification of
the boxed area on the right side. Notice the open, spongy
texture of the echinoid plate. (SEM photomicrograph)
47
Plate 13. Early stage syntaxlal cernent overgrowth (S) on echinoid
plate fragment. Large straight edged crystals are dolomite
rhombs (D). (SEM photomicrograph, ISOOx)
Plate 14. Later stage syntaxlal overgrowth (S) on echinoid plate
fragment (E). The open, spongy structure of the echinoid
plate has been obliterated by syntaxlal cement. Notice how
the large calclte crystals are growing perpendicular to the
plate surface. (SEM photomicrograph, 150x)
48
porosity. Two varieties of pore filling cement, blocky and drusy, occur
in Pungo River sediments. Blocky cement is the predominant pore filling
cement.
Blocky cement crystals are greater than 30um in length, subequant
to equant in shape, and anhedral to subhedral in form. Where pore space
is relatively large, crystal size increases to the center of the pore.
Blocky cement occurs in two Pungo, River lithologies. In moldic
microsparites it partially to totally occludes moldic secondary porosity
(Plate 15); contact between blocky cement and prismatic cement, which
often lines the molds, is abrupt. In calcite cemented quartz sandstone
(seismic unit BBF-2, core OB-92) blocky cement is gradational with
microspar and occasionally with drusy cement.
Drusy cement (Plate 16), in which crystals are also larger than
30um in length, is gradational with radial rim cement. Crystal size
increases away from pore walls. Drusy cement occurs only in calcite
cemented quartz sandstones in interparticle pore spaces between fossils.
Loucks (1977) suggested that increasing crystal size of pore
filling cement toward the center of pores is indicative of fresh water
cementation. Blocky cement has been interpreted by Longman (1980) to be
indicative of a fresh water phreatic diagenetlc environment. Pore
fluids with Mg/Ca ratios of 1:1 or less Indicate a fresh water
diagenetlc environment and have been shown to form blocky calcite cement
(Folk, 1974; Folk and Land, 1975).
Microspar. Microspar is characterized by equant, subhedral to
euhedral, calcite crystals with a generally accepted lower size limit of
49
Plate 15. Blocky pore filling cernent (B) and microspar (M) in moldic
mlcrosparite. Remaining void space in the mold is black.
Quartz (Q) is white to blue, subangular to subrounded
grains. Core OB-94, 1.00-1.25m. (crossed niçois, 160x)
Plate 16. Drusy cement (D) on barnacle plate. Core OB-92, 3.25-3.50m.
(crossed niçois, 25x)
50
4um, but an upper limit that is still debated. Folk (1959, 1965)
suggested an upper size limit of lOum. Leighton and Pendexter (1962)
believed microspar should include equidimensional calclte crystals up to
30um and Bossellinl (1964) used a size range of 4-30um for his micrite
II. The latter is used in this study as the size range of microspar.
Microspar is abundant where Pungo River carbonate sediments are
partially lithifled (Plate 15). Where it is mixed with clays and other
matrix materials, microspar occurs in smaller concentrations. This may,
in part, be an artifact of sampling because most thin sections used for
this study are in partially llthified sediment, while the majority of
Pungo River carbonate sediments in Onslow Bay are unconsolidated.
Two methods of microspar formation have been suggested in the
literature. Folk (1974) suggested that when aragonite or high-Mg
calcite mud inverts to low-Mg calcite. Mg ions expelled from the mud
form a "cage" around the 2-3um calcite crystals. Magnesium ions inhibit
further growth of the micrite. Removal of Mg ions by fresh water
flushing, dolomltlzation, or absorption of Mg by clay minerals results
in Increased calcite crystal growth. This two step process of lime mud
Inversion and later crystal growth, known as aggrading neomorphism, is
the generally accepted mode of microspar formation (Folk, 1959, 1965).
SEM studies of aragonite-dominated lime muds show that aragonite
laths are calcitized during one period of neomorphism, resulting in the
co-occurrence of micrite and microspar (Lasemi and Sandberg, 1984).
Mixed crystal sizes do not necessarily mean that micrite has been
neomorphosed to raicrospar.
Because microspar in the Pungo River Formation occurs with other
51
calcita cements which indicate a fresh water phreatic environment, it
probably formed via fresh water flushing.
Dolomite
Dolomite in the Pungo River Formation is present as
matrix-supported euhedral rhombic crystals or aggregates of rhombs.
According to the dolomite textural classification system of Gregg and
Sibley (1984), Pungo River dolomite is idiotopic-P (matrix supported
euhedral rhombs with a porphyrotopic texture). Pungo River dolomite
rhombs range in size from 5 to 120 urn in diameter and those in the fine
sand-sized fraction compose up to 2.4% of the total sediment. However,
dolomite is most abundant in the mud fraction. X-ray diffractometry and
insoluble residue analyses show that dolomitic mud constitutes up to
50.8% of the total sediment (Appendix B).
Dolomite in the FPF and BBF seismic sequences has even, plane
surfaces (Plates 17 and 18). In the AF sequence, rhombs are pitted and
have uneven surfaces (Plates 19 and 20). Edges of rhombs in the AF
sequence are not rounded, which argues against a detrital origin. Allen
(1985) described the uneven surfaces as "flame-like" textures, similar
to those described by Weaver and Beck (1977) in Miocene sediments of the
Atlantic Coastal Plain. She stated that pitting of dolomite rhombs was
caused by dissolution of a calcium carbonate precursor, rather than
dolomite dissolution. I believe the pitting and uneven surface textures
are due to dolomite dissolution because calcareous fossils in this
sequence appear only sllghty etched.
Most sand and coarse silt-sized dolomite rhombs in the Pungo River
52
Plate 17. Washed sample of euhedral dolomite rhombs in the BBF
sequence. Core OB-1, 4.50-4.75m. Notice opaque white cores
(C) in rhombs, (reflected light, 50x)
Plate 18. Euhedral dolomite rhombs in the BBF sequence. Notice the
plane, even surfaces of the rhombs. Core OB-1, 4.50-4.75m.
(SEM photomicrograph, lOOOx)
53
Plate 19. Dolomite rhombs In the AF sequence. Notice the uneven
surface texture and dissolution pitting. Core OB-33,
4.50-4.75m. (SEM photomicrograph, 2000x)
Plate 20. Dolomite rhomb tn the AF sequence illustrating
"flame-texture" produced by dissolution. Core OB-33,
4.50-4.75ra. (SEM photomicrograph, 2000x)
54
Formation have an opaque white, roughly spherical core that is about
one—fourth the size of the enclosing rhomb. The core is surrounded by
clear, colorless dolomite (Plate 17). These rhombs are not zoned, nor
are they hollow when viewed in thin section. However, dolomites in
chert nodules of core OB-123 (seismic unit FPF-2) are well zoned (Plate
21) with a core that has a "spongy" texture; a few of these cores are
partially to almost totally hollow. SEM studies of dolomite in chert
nodules in the AF sequence indicate a few of the rhombs are hollow
(Plate 22).
Dolomite occurrence in the Pungo River Formation is sporadic (Table
6). In some cores dolomite Increases up-section, in some it decreases
up-sectlon, and in others there is no recognizable trend. This may
reflect the actual occurrence of dolomite, or it could be an artifact of
the sampling Interval or the methods used to estimate dolomite
abundance. Thin section point counts of dolomite in some lithologies
are not possible because of the fine grained nature of the dolomite.
Because most of the dolomite is mud-sized, quantitative x-ray
diffractometry using standards is needed to determine the true abundance
and distribution of this dolomite.
Composition of Pungo River dolomites was measured by three methods:
x-ray diffactometry, staining for ferroan dolomites, and microprobe
analysis. Comparison to x-ray diffraction peak positions of ferroan
dolomite (ankerlte) shows that Pungo River dolomite matches closely
(Table 7). Thin sections were stained by the method of Katz and
Friedman (1965) to detect iron. Ferroan dolomite, which generally has
about 1/3 of its Mg replaced by Fe, stains blue; iron-poor dolomite does
55
Plate 21. Zoned dolomite in chert nodule. Core OB-123, 6.74m.
(crossed niçois, 160x)
Plate 22. Hollow dolomite in chert nodule. Core OB-35, 8.00m.
(SEM photomicrograph, 1500x)
56
Core Dolomite Core Dolomite
Depth (m) Sand Matrix X-ray Depth (m) Sand Matrix X-ray
OB-1 OB-16
4.50 1.6 15.6 C+D 1.50 tr 5.8 D
5.25 2.4 — - 5.50 0 8.2 D
5.75 0.7 11.1 C+D
6.50 0.2 9.0 C+D OB-91
8.00 0.7 3.7 C+D 3.50 0.8 8.6 C+D
5.50 0.6 6.4 C+D
OB-111
0.50 0.1 17.9 C+D OB-35
2.50 1.7 43.1 C+D 2.75 0.1 37.9 C+D
4.25 0 25.0 C 5.25 0.1 36.8 C+D
5.50 0 37.3 C 7.75 0.2 34.1 C+D
6.25 0 22.9 C
7.50 0 37.4 C OB-3 8
8.00 0 13.0 C 3.50 0.5 22.8 D
6.50 tr 27.7 D
OB-2 7 8.75 0 2.2 D
1.0 0 5.1 N
3.0 0 10.3 C OB-49
5.0 0 15.7 c 1.75 0 16.2 D
7.0 0 16.4 C+D 4.75 0 9.2 D
7.75 0 8.9 D
Table 6. The % of dolomite in the sand fraction (Sand), % of carbonate mud
(Matrix), and x-ray determinations of the type of carbonate (C =
calcite; D = dolomite; N = none) in the matrix (X-ray) are shown
for a representative group of samples. Dolomite can increase up
section, down section, or have any distribution.
57
Dolomite Ankerite Pungo River dolomi
26 d(A) I 29 d(A) I 26 d(A) I
30.975 2.886 100 30.975 2.886 100 31.00 2.89 100
51.150 1.786 30 50.350 1.812 6 50.35 1.81 9
51.300 1.781 30 50.950 1.792 6 50.80 1.80 5
41.175 2.192 30 41.025 2.199 6 41.15 2.20 4
50.600 1.804 20
45.000 2.015 15 44.875 2.020 3 44.95 2.02 3
1.389 15 1.391 1
33.575 2.670 10 33.375 2.685 3
37.400 2.405 10 37.300 2.411 3 37.40 2.41 1
59.850 1.545 10 59.725 1.548 2
1.431 10 1.436 1
Table 7. Major superstructure reflections of dolomite, ankerite, and
Pungo River dolomite arranged in order of decreasing intensity
of Pungo River dolomite. Peak positions of dolomite and
ankerite are from Howie and Broadhurst (1958). Intensity has
been recalculated to 100%.
58
not stain. Pungo River dolomite did not stain, which suggests it is not
iron-rich. Microprobe analyses of dolomite rhombs from seismic unit
BBF-6 (core OB-1) show no iron enrichment, but instead indicate a
calcium-rich dolomite (Table 8).
Hurlbut and Klein (1977) stated that sedimentary dolomite generally
deviates from its stoichiometric formula ofCaMg(C02)2 with Ca;Mg
ratios of 47.5:52.5 to 58.0:42.0. Dolomite in seismic unit BBF-6 has a
high Ca:Mg ratio (Ca:Mg = 57:41) indicating that it is a
nonstoichiometric, calcium-rich dolomite.
Stoichiometric dolomite is largely from deeply burled sediments and
metamorphlc rocks (Land, 1983). Most dolomites contain excess calcium
and lack the degree of ordering of Ca and Mg in their structure
characterized by stoichiometric dolomite (Goldsmith and Graf, 1958;
Goldsmith and others, 1962; Lumsden and Chimahusky, 1980).
Calcium-rich, nonstoichiometric dolomite has been called protodolomite
in belief that it is a precursor to stoichiometric dolomite (Graf and
Goldsmith, 1956; Gaines, 1977). Attenuated superstructure reflections
(weakened x-ray peaks) in x-ray diffractograms has been cited as proof
that dolomite is disordered. Reeder (1983) stated that if these
nonstochlometrlc dolomites do, in fact, have superstructure reflections,
then they are dolomites and should be called dolomite; if they do not
have superstructure reflections, they are not dolomites. Land (1980)
suggested that the term protodolomite be dropped because most dolomites
are nonstochlometrlc. Allen (1985) stated that Pungo River dolomites
have attenuated superstructure reflections. X-ray diffractograms
included in her study show superstructure reflections from 20° to
GRAIN SAMPLE AREA CaO MgO FeO MnO Na^O AI2O3 SÍO2 K^O TiO^
1 D41A C 34.807 17.538 0.003 0.000 0.027 0.000 0.018 0.001 0.000
1 D41B R 33.943 16.907 0.000 0.047 0.011 0.000 0.359 0.020 0.000
1 D41C R 35.367 18.227 0.104 0.017 0.045 0.039 0.038 0.024 0.000
2 D42A C 36.089 17.641 0.000 0.017 0.067 0.000 0.000 0.033 0.000
2 D42B R 33.801 16.907 0.000 0.010 0.036 0.078 0.129 0.025 0.050
2 D42C R 33.896 17.382 0.023 0.000 0.065 0.000 0.029 0.021 0.051
3 D43A C 33.085 18.350 0.710 0.000 0.093 0.171 0.796 0.088 0.009
3 D43B R 37.764 19.556 0.000 0.000 0.058 0.000 0.070 0.000 0.060
4 D44A C 33.561 17.769 0.022 0.044 0.052 0.000 0.100 0.008 0.025
AVERAGE OF CENTERS 34.386 17.825 0.184 0.015 0.060 0.043 0.229 0.033 0.002
AVERAGE OF RIMS 34.954 17.796 0.025 0.015 0.043 0.023 0.125 0.018 0.032
AVERAGE 34.701 17.809 0.096 0.015 0.050 0.032 0.171 0.024 0.022
Stochtoraetrlc 30.411 21.857
Dolomite
Table 8. Mlcroprobe analyses of dolomite from core OB-1 (seismic unit
BBF-6) by S.R. Riggs on 2/14/84. Oxides are in weight %.
(Area = area of analysts of dolomite: C - center; R - rim.)
60
50°26 for bulk sediment samples (not dolomite concentrates).
Continuing x-ray diffractograms until 52°26 reveals that a couplet
of x-ray peaks indicative of dolomite is not present, but a couplet
indicative of ferroan dolomite is present (Fig. 9).
Dolomite crystal shape is dependent on the temperature at which it
formed. Gregg and Sibley (1984) suggested that at a "critical
roughening temperature" (CRT) of between 50° and 100°C dolomite
will form anhedral rather than euhedral crystals. They also stated that
calcium-rich dolomite may have a lower CRT due to substitution of Ca for
Mg. Fungo River dolomite is calcium-rich and euhedral, which suggests
that it formed at temperatures below 50°C.
Oxygen isotope analyses of Fungo River dolomites from Onslow Bay
and the Aurora Area indicate formation in marine pore waters at
temperatures of 4° to 13°C (Allen, 1985). Carbon isotope
analyses indicate that most of its carbon is from an inorganic calcium
carbonate precursor (Allen, 1985). Low concentrations of Sr, Fe, Mn,
and Zn within the dolomite indicate dolomite formation during shallow
burial in marine pore waters (Allen, 1985). Baker and Kastner (1981)
showed that, at concentrations as low as 5% of its seawater value,
2—
(SO^) inhibits dolomitizatlon of calcite. Bacterial sulfate
reduction occurs 0.01 to 10 m below the sediment-water interface
(Fisciotto and Mahoney, 1981), enhancing dolomite formation by removing
2—
dissolved (SO^) , producing alkalinity, and causing the
formation and exchange of for Mg^^ from opaline silica
(opal-A) (Baker and Kastner, 1981). This information Indicates that
Fungo River dolomite formed from an inorganic calcium carbonate
61
precursor In the marine environment during early diagenesis after
bacterial sulfate reduction, possibly within centimeters of the sea
floor (Allen and Baker, 1984; Allen, 1985). This Interpretation also
helps explain the sporadic occurrence of the dolomites. Where bacterial
2-
sulfate reduction has not removed enough (SO^) from the
sediments, possibly due to a scarcity of organic sediment or to rapid
sedimentation, dolomite formation could be inhibited which could result
in a dolomite distribution that has no relationship to other dlagenetlc
profiles.
Silicification
Replacement of pre-existing sediment and void filling by authigenic
silica are the processes involved in silicification. The silica
classification of Folk and Pittman (1971) is used to describe varieties
of silica in siliclfled Pungo River sediments. Megaquartz comprises
crystals greater than 20um in diameter and those of microquartz are less
than 20um. Microquartz is further divided into chalcedony (fibrous) and
microcrystalline quartz (equant).
Three patterns of silicification in Pungo River sediments of Onslow
Bay include: 1) chert nodules, 2) chalcedonic cement, and 3) selective
replacement of fossils. These types of silicification are interrelated
and will not be divided into separate headings.
Three lithologically different types of chert nodules occur in
Pungo River sediments. Characteristics common to all three include a
central portion which reflects an original detrital sand grain
mineralogy that is similar to the surrounding sediments. The outer
62
surface of the nodules Is the color of the surrounding sediments and is
cemented predominantly by calcite cement.
Type 1 chert nodules are present in seismic unit AF-1, core OB-35
(Plate 23). The center of these nodules is gray with a dull or matte
surface texture where cryptocrystalline silica has totally replaced
carbonate mud in the sediment. Microcrystalline quartz has replaced
calcareous fossils (foramlnlfers, molluscs, barnacles, echlnoids, and
ostracods) and calcite rim cements present associated with them (Plates
24 and 25). The shapes of fossils and carbonate cements are mimicked by
microcrystalline quartz, making identification easy. Microcrystalline
quartz has replaced the central portion of barnacle plates, leaving a
mlcritic rim surrounding the microquartz. Voids are often lined with
chalcedony (Plate 26). Detrital quartz composes 11.4% of the nodules
and unreplaced fossils constitute another 9.7%. Two sizes of dolomite
rhombs are present in Type 1 nodules. Larger rhombs, which constitute
5.8% of the nodules, average 80um in diameter, and have opaque rounded
cores approximately 20um in diameter. Smaller rhombs are 10 to 20um in
diameter and do not appear to have a core. The latter could not be
point counted because of their small size, but constitute approximately
35% of the nodules. Silicification of fossils is most intense near the
center of nodules and generally decreases outward. A thin transition
zone, 1-2 mm thick, is present between the silictfled portion of the
nodules and the outer calcite-cemented surface. In thin section this
transition zone is cloudy and slightly opaque, and it appears to be
where clay in the sediment was expelled from the portion of the nodule
being siliclfied (Plate 27).
63
Plate 23. Chert nodule from seismic unit AF-1. The gray central area
of the nodule is the silicifled part; the white outer rim is
calclte cemented, dominantly unreplaced carbonate sediment.
Core OB-35, 8.00m.
64
Plate 24. Photomicrograph of chert. Fossils Include barnacles (B),
ostracods (C), foraminifers (F), molluscs (M), and echinoids
(E). Dolomite (D) and subangular to subrounded quartz (Q) is
also present. Core OB-35, 8.00m. (transmitted light, I60x)
Plate 25. Photomicrograph of chert. Same field of view as Plate 24.
Almost all fossils and calcium carbonate cements are
stlicified whereas dolomite rhombs are not replaced,
(cross niçois, 160x)
65
Plate 26. Chalcedony lining a void in chert nodule. Core OB-35,
8.00m. (crossed niçois, 160x)
Plate 27. Clay-rich transition between zone of intense silicification
and carbonate cemented sediment. Core OB-35, 8.00m.
(transmitted light, 25x)
66
Type 2 chert nodules are found in cores OB-38, OB-40, and OB-44 in
seismic unit AF-1 and in core OB-47 in unit FPF-2. The centers of these
nodules are gray with a glossy appearance. Detrital quartz is very
sparse (0.3%) and calcareous fossils are nonexistent. Dolomite is very
fine-grained, averaging lOum in diameter and ranging in size from 5 to
40um. Again, dolomite is too fine grained to be point counted, but
constitutes approximately 40% of the nodules. Small voids are lined by
chalcedony and filled with microcrystalline quartz. Type 2 nodules also
have a thin, clay-rich transistlon zone between the Intensely silicified
central part and the calcite-cemented outer surface.
Core OB-123 in seismic sequence FPF-2 contains many large Type 3
chert nodules averaging approximately 8cm by 3cm. Sedimentary
structures such as burrows and bedding were very well preserved during
silicification (Plate 28). Silicification appears to have paralleled
bedding, probably due to permeability between bedding planes. The
nodules contain abundant detrital quartz (44.1%), glauconite (1.3%), and
well zoned dolomite (10.5%) (Plate 21). Most dolomite rhombs contain a
core that appears to be dolomite with a spongy texture. In a few of the
largest rhombs, the spongy core has been partially to almost tatally
dissolved. Fossils are not present in the nodules. A sharp textural
and mineralogical change occurs at the contact between the central part
of the chert nodule and the outer rim (Plate 29). The predominant
component of the rim is fine (20um) dolomite, with lesser concentrations
of what appears to be clay which was expelled from the central part of
the nodules. Detrital quartz concentration in the rim drops off to
about 2%
67
Plate 28. Chert nodule showing bedding preserved by silicification.
Core OB-123, 5.00-5.25m. Nodule is 7cm long.
Plate 29. Contact between area of intense silicification and rim of
chert nodule showing the sharp mlneralogical and textural
change. Core OB-123, 6.74m. (crossed niçois, 25x)
68
X-ray diffractometry of the chert nodules shows the silica to be
opal-CT with minor quartz. The quartz probably detrital and authigenic
because both detrital quartz and microquartz occur in the nodules.
Scanning electron microscopy of the nodules shows the presence of
opal-CT lepispheres (Plates 30 and 31) and spagetti-like structures that
appear to have some degree of crystallinity (Plate 32).
Chalcedony is the cementing agent in quartz sandstone (Plate 33)
located in core OB-58 at 7.40 m (seismic unit AF-2). It comprises 32.7%
of the rock volume. Chalcedonic fibers average 25um long and line all
pore spaces. Remaining pore space is filled by either botryoidal
chalcedony or microcrystalline quartz. Dlagenetic silica appears to
have almost totally replaced an original carbonate matrix. In the few
areas where any carbonate is left, very minor dolomite and a few
partially replaced barnacle plates are present. The central part of the
barnacle plates is replaced by microcrystalline quartz and is surrounded
by an unreplaced micritlc rim in the outer portions.
In core OB-34 at 2.00 m (seismic unit AF-3) echinoids are partially
replaced by chalcedony not associated with chert nodules or void lining
cements. This chalcedony has only replaced the central portion of
echlnoid plates and spines.
Potential sources of silica for Pungo River silica authigenesis
include diagenesls of volcanic glass and biogenic material. Marine
waters contain an average of 3 ppm Si (Anlkouchlne and Sternberg, 1981)
and are undersaturated with respect to silica (Reich and von Rad, 1979).
Therefore, marine pore waters have to be enriched by some outside source
for authigenic silica to form.
69
Plate 30. Lepispheres in chert nodule. Core OB-35, 8.00m.
(SEM photomicrograph, 5000x)
Plate 31. Lepispheres in chert nodule. Core OB-35, 8.00m.
(SEM photomicrograph, 5000x)
70
Plate 32. Spagetti-like structures In chert nodule. Notice the
euhedral dolomite rhomb floating in the cryptocrystalline
silica. Core OB-35, 8.00m. (SEM photomicrograph, 4000x)
Plate 33. Chalcedonic cement in quartz sandstone. Core OB-58, 7.40ra.
(crossed niçois, 160x)
71
Volcanic glass has been postulated to be the source of silicia in
zeolites at Aurora (Rooney and Kerr, 1964). However, no volcanic glass
has been found in the Pungo River Formation, either by Rooney and Kerr
(1964) in the Aurora Area or by Lyle (1984) or this study in Onslow Bay.
If volcanic glass had ever been present, it already has been altered
beyond recognition.
Biogenic silica has been widely documented as a source of silica in
deep sea cherts. Diatoms are often abundant in the mud fraction of the
Pungo River Formation (Plate 8). The presence of unaltered diatoms,
radiolarians, and siliceous sponge spicules in sediment above and below
zones of silicification in the Pungo River Formation suggests that
biogenic silica was a source of authigenic silica. Sand-sized siliceous
microfossils in core OB-47 (seismic unit FPF-2) decrease sharply in
abundance above a zone of chert nodules (Fig. 9). Most diatoms and
radiolarians are silt-sized or smaller and their abundances in the mud
fraction have not yet been carefully charted.
Siliceous organisms fix silica as a highly disordered, nearly
amorphous, hydrous silica termed opal-A by Jones and Segnit (1971) and
cover their shells with an organic coating. Upon death the organic
coating decays, exposing the shells to ocean water where dissolution
begins (Lewln, 1961). Siliceous biogenic material that makes it into
the sediment column generally goes through a maturation process from
opal-A (siliceous ooze) to opal-CT (porcellanite) and ultimately to
quartz (chert). Opal-CT is a disordered alpha-cristobalite with some
tridymite stacking (Jones and Segnit, 1971). It occurs as 5-lOum
lepispheres and is the type of silica found in most Cenozoic and some
72
DEPTH (M)
BELOW
SEOmSUT
SURFACE
PERCENT
Figure 9. Vertical distribution of sand-size siliceous fossils and
chert nodules In FPF-2 (core OB—47). Abundance of siliceous
fossils Indicated by dots; presence of chert nodules
Indicated by X.
73
Mesozoic cherts. Opal-CT lepispheres -can be seen in Pungo River cherts
(Plates 32 and 33), which are actually "porcellanites" because opal-CT
is the predominant type of silica present in the nodules.
Kastner and others (1977) found that transformation of opal-A to
opal-CT is faster in pure carbonates than in clayey sediments. This may
be one reason why all of the biogenic silica in Pungo River sediments
has not been redeposited as authlgenlc silica. Alkaline conditions are
necessary for opal-CT formation (Kastner and others, 1977). Dissolution
of carbonates provides alkalinity. As the silicification front moves
through the sediment, carbonate is lost to dissolution (Wise and Weaver,
1974). Clays are expelled from the silicified zone and are concentrated
along the outside of the silicification front (Lancelot, 1973). Some of
the carbonate is reprecipitated beyond the silicification front,
cementing the carbonate rock (Wise and Weaver, 1974). This appears to
be the mechanism by which Pungo River chert nodules, "floating" in
unlndurated carbonate sediment, have developed indurated calcium
carbonate rinds underlain by clay-rich transition zones.
Zeolites
The zeolite, cllnoptilolite, has been found in Pungo River
sediments in the Aurora Area (Rooney and Kerr, 1964) and Onslow Bay
(Lyle, 1984; Snyder and others, 1984; this study). Lyle (1984) noted
that cllnoptilolite occurs in the BBF seismic sequence as single
euhedral lath-shaped crystals with a broken edge. He suggested
reworking of previously deposited zeolites to account for the broken
edges of these fine silt-sized crystals.
74
Foraminiferal tests in unit FPF-2 are usually partially to totally
filled with euhedral clinoptllolite crystals and minor pyrite framboids
(Plate 34) which have overgrown clinoptllolite crystals (L. Moretz,
pers. comm.). Cores OB-27, 63, and 70 show the best examples of
zeolite-filled internal molds of foraminifers (Plate 35). No opal-CT
lepispheres have been seen associated with the clinoptllolite in
foraminifers.
Clinoptllolite occurs in the Atlantic Ocean more frequently with
siliceous organisms than with volcanic material (Reich and von Rad,
1979). Common associations are: clinoptllolite with opal-CT in pelagic
clays and hemipelagic carbonaceous marls and shales (von Rad and Rosch,
1974); poorly preserved euhedral clinoptllolite and opal-CT lepispheres
on the Internal walls of radiolarian tests (Berger and von Rad, 1979);
euhedral, and less commonly, massive clinoptllolite filling
foraminiferal tests after formation of early diagenetic calcite and
opal-CT lepispheres (Reich and von Rad, 1979). Reich and von Rad (1979)
state that authigenlc clinoptllolite can form in sediments if 1) there
is a sufficient supply of aluminum, alkali, and alkali-earth ions
available and 2) the pore waters are undersaturated with silica with
respect to opal-CT. Low silica conditions can occur after precipitation
of opal-CT and before opal-CT formation. Negative Eh and pH associated
with organic-rich sediments also appears to favor clinoptllolite
formation (von Rad and Rosch, 1974).
Known clinoptllolite associations and modes of formation favor a
biogenic source of silica for Pungo River zeolites. No siliceous
organisms are present in unit FPF-2 where clinoptllolite is found in the
75
Plate 34. Clinoptilolite filled Internal molds of foramlnifers. Core
OB-27, 1.00-1.25m. (reflected light, 25x)
Plate 35. Clinoptilolite internal mold of a benthic foraralnifer
(Lentlcullna). Core OB-27, 1.75-2.00m. Photo courtesy
of Walter Hale. (SEM photomicrograph, ll2x)
76
Frying Pan Area, but are present elsewhere in FPF-2. These sediments
are organic-rich, with 2 to 4% organic carbon in the total sediment in
core OB-63 (S.R. Riggs, unpub. data). Because no opal-CT lepispheres
are associated with the clinoptilolite, it probably formed in sediments
with fewer siliceous organisms than those associated with chert. Sodium
could have been supplied by marine pore waters while potassium, calcium,
and aluminum were supplied by clays. The organic-rich sediments
probably caused low Eh and pH conditions to exist. Foraminifers were
probably buried while clinoptilolite was growing so that pore waters
were poorly oxgenated. Oxygen in the pore waters may have been mostly
removed by zeolites, resulting in later of growth of pyrite.
Summary
Pungo River sediments show a variety of diagenetlc components which
have been produced by early marine and fresh water phreatic diagenesis.
An Interpretation of the relative timing of Pungo River diagenetlc
processes is summarized in Figure 10. The type and extent of diagenesis
in each lithology will be discussed in the description of each seismic
sequence
77
EVENT RELATIVE TIME
EARLY LATE
« »
ISOPACHOUS
CEMENT
PRISMATIC
CEMENT
SYNTAXIAL
CEMENT
BLOCKY
CEMENT
DRUSY CEMENT
DISSOLUTION
OF MOLLUSCS
DOLOMITE
SILICIFICATION
ZEOLITES
Figure 10. Relative timing of dlagenetlc events In the Fungo River
Formation. Uncertainty of timing Is Indicated by ?.
78
LITHOLOGIC DESCRIPTIONS
FPF Sequence
The FPF sequence was deposited during the late Burdigalian (Waters,
1983). Thickness of this sequence ranges from 0 meters at its erosional
updip truncation to more than 70 meters in the subsurface (S.W.P.
Snyder, 1982). Snyder divided the FPF sequence into six smaller seismic
units labeled FPF-1 to FPF-6 from oldest to youngest (Fig. 1).
Table 9 summarizes the average abundance of mineralogical and
faunal components in each seismic unit from north to south in Onslow Bay
(15m profile; 22m profile; profiles 1-8, 1-4, 1-5; and Frying Pan (FP)
Area). Figure 8 locates each seismic unit, all relevant seismic
profiles, and the FP area. Average abundance and distribution of the
major mineralogical components (carbonate, phosphate, silica,
siliciclastic sand and mud) are summarized in Table 10. All data in
Tables 9 and 10 is compiled from reflected light microscopy and
insoluble residue data (Appendices A and B) except for FPF-1 on the 22m
profile (Table 10) which is from thin section data (Appendix C).
Seismic unit FPF-1
Seismic unit FPF-1 was cored along the 22ra profile, 1-4, and in the
Frying Pan Area. The lithology of core OB-134, located on the 22m
seismic profile, is a slightly fossiliferous (8.4%), quartz-rich
(35.9%), microsparlte. It is well Indurated and moldlc where bivalves
have been leached away. Body fossils include barnacles (3.6%),
echinoids (2.9%), foramlnifers (1.3%), and bivalves (0.6%). No dolomite
Seismic Unit FPF-1 FPF-2 FPF-3 FPF-4 FPF-5 FPF-6
Area 22m 1-4 FP 22m 1-4 FP 1-4 FP 15m 1-8 1-4 1-8 FP
# of Samples 1 3 13 2 7 15 3 4 3 3 4 4 5
Molluscs 0.6 tr 0.3 0.8 tr 0.1 0.2 tr 19.8 0.3 3.4 2.1 0.1
Barnacles 3.6 tr 2.6 0.1 tr tr 0.7 tr 3.0 10.6 3.0 11.3 0.1
Bryozoans 0 tr 0.7 tr tr tr tr tr 0 0.2 0.3 0.5 tr
Echlnolds 2.9 0 0.5 0.4 0.1 tr 1.1 tr 0.1 2.3 1.8 5.9 7.7
Ostracods 0 0 tr tr 0 0 0.1 0 tr tr 0 0 0.1
B. Forams I.O 0 14.8 0.1 tr 3.0 1.0 2.0 0.1 0.9 0.6 1.4 8.7
P. Forams 0.3 0 3.7 0.6 tr 1.4 0.2 0.1 0 0.1 0.2 0.3 6.1
Carbonate 0 tr 1.2 0.6 0.1 0.5 2.7 tr 0.3 4.9 2.7 4.9 6.7
Spar 7.1 tr 0.4 0 tr 0.5 3.4 tr tr tr 1.6 0.5 1.7
Dolomite 0 0 0.1 0 0 tr 0 tr 0 0.1 0 0.1 0
Chert 0 0 tr 0 0.7 0 0.5 0 0 0 0 0 0
Diatoms 0 0 0 0 0.6 tr 0 tr 0 0 0.1 0 0
Radlolarla 0 0 0 0 tr tr 0 0.2 0 0 0 0 0
Spicules 0 0 0 0 tr tr 0 0.1 0 0 tr 0 0
Skel Phos 0 1.5 3.5 0.6 0.3 0.9 0.4 0.1 0.5 0.5 0.2 0.3 1.0
Phosphate 0.3 3.1 16.3 tr 0.4 1.5 0.9 0.3 tr 0.2 0.6 0.5 0.6
Glauconite 0 0 0 0 tr tr tr 0 tr 0 tr tr 0
Opaques 1.0 0 tr 0 tr tr 0.4 0 0 0.1 tr tr 0
Other 0 0 tr 0.1 tr 0.3 0 tr 0 0 0 0 0
Qtz Sand 35.9 47.5 17.8 74.1 33.8 16.0 71.3 3.3 65.8 59.5 30.0 45.2 35.6
Insol Mud 0 31.9 19.5 20.5 48.3 64.1 11.8 75.2 6.3 17.1 38.6 7.0 17.3
Carb Mud 47.2 15.9 18.5 2.1 15.5 11.8 5.5 18.7 4.1 3.4 17.0 20.0 14.3
TOTALS 99.9 99.9 99.9 100.0 99.8 100.1 100.1 100.0 100.0 100.2 100.1 100.0 100.0
Table 9. Summary of abundance and distribution of all mlneraloglcal and faunal
components (In X of total sediment) In the FPF seismic units. All
numbers are based on reflected light microscopy and Insoluble residue data
(Appendices A and B) except for data on FPF-1 along the 22m profile which
is from Appendix C. (Carbonate - unidentifiable carbonate fragments; Spar =
calcite cement; Qtz Sand “ slllclclastlc sand; Insol Mud « Insoluble mud;
Garb Mud - carbonate mud.)
Seismic Unit FPF-1 FPF-2 FPF-3 FPF-4 FPF-5 FPF-6
Area 22m 1-4 FP 22m 1-4 FP 1-4 FP 15m 1-8 1-4 1-8 FP
# of Samples 1 3 13 2 7 15 3 4 3 3 4 4 5
Fossils 8.4 tr 23.8 2.6 0.2 5.0 6.0 2.1 23.3 19.3 12.0 26.4 29.5
CARBONATE Spar 7.1 tr 0.4 0 tr 0.5 3.4 tr tr tr 1.6 0.5 1.7
CONSTITUENTS Dolomite 0 0 0.1 0 0 tr 0 tr 0 0.1 0 0.1 0
Carb Mud 47.2 15.9 18.5 2.1 15.5 11.8 5.5 18.7 4.1 3.4 17.0 20.0 14.3
Carbonate 62.7 15.9 42.8 4.7 15.7 17.3 14.9 20.8 27.4 22.8 30.6 47.0 45.5
Silica 0 0 tr 0 1.3 tr 0.5 0.3 0 0 0.1 0 0
MAJOR Phosphate 0.3 4.6 19.8 0.6 0.7 2.4 1.3 0.4 0.5 0.7 0.8 0.8 1.6
CONSTITUENTS Others 1.0 0 tr 0.1 tr 0.3 0.4 tr 0 0.1 tr tr 0
Qtz Sand 35.9 47.5 17.8 74.1 33.8 16.0 71.3 3.3 65.8 59.5 30.0 45.2 35.6
Insol Mud 0 31.9 19.5 20.5 48.3 64.1 11.8 75.2 6.3 17.1 38.6 7.0 17.3
TOTALS 99.9 99.9 99.9 100.0 99.8 100.1 100.2 100.0 100.0 100.2 100.1 100.0 100.0
table 10. Summary from Table 9 of abundance and distribution of major
mlneraloglcal components (In % of total sediment) in FPF seismic
units. (Spar = calclte cement; Qtz Sand = slllclclastlc sand;
Insol Mud = Insoluble mud; Garb Mud = carbonate mud.)
81
Is present.
In central Onslow Bay along seismic profile 1-4, unit FPF-1 is a
phosphatlc (4.6%), muddy (47.8%), quartz sand (Table 6). Carbonate is
present only as 15.9% calcite mud and as trace percentage of bivalves,
barnacles, and bryozoans.
In the Frying Pan Area, FPF-1 grades up-section from a quartz-rich
(17.8%), foraminiferal (18.5%), muddy (38.0%), phosphorite (Table 9) to
a phosphatlc (3.6%), quartz-rich (6.9%), fossiliferous (41.6%)
biomicrosparite (Table 11). In core OB-115, the most extensively
sampled of all Frying Pan FPF-1 cores, fossils and matrix increase
up-section while slllciclastic sand and phosphate decrease (Fig. 11).
The basal part of unit FPF-1 in the Frying Pan Area contains an
average of 18.5% carbonate mud in the form of calcite or calcite with
dolomite. Dolomite averages 0.1% in the very fine sand fraction.
Predominant fossils are benthic foraminifers (14.8%), planktonic
foramlnifers (3.7%), and barnacles (2.6%). All barnacles and most
bryozoans are rounded, stained gray, and appear to have been
transported. Foraminifers and echlnoids are well preserved and appear
not to have undergone transportation. Plate 2 shows the washed sand
fraction of basal FPF-1 (core OB-115).
The biomicrosparite "cap" contains a diverse assemblage of fossils
including barnacles (13.7%), bryozoans (8.3%), bivalves (8.3%),
echlnoids (5.3%), and benthic foraminifers (2.2%). Planktonic
foraminifers, ostracods, crab claws, dasycladacean and coralline algae
are present in abundances of less than 0.3% (Table 11). Plate 4 is a
thin section through the carbonate cap in core OB-115.
Sample Moll Barn Bry Ech Ost Bf Pf Alg Garb Spar Mlc Phos 0th Qtz
20-0.50 4.9 18.1 2.0 4.3 0.3 0.8 0 0.3 10.6 4.0 43.6 3.7 1.7 5.7
64-0.75 9.6 19.4 4.8 4.1 0.3 1.3 0.3 0 2.2 1.3 43.6 2.5 0 10.5
64-1.75 9.6 9.6 13.0 4.6 0.3 1.9 0 0 1.9 0.3 50.2 1.5 0 7.1
64-2.75 4.8 4.1 0 4.1 0 4.1 0.7 0 2.8 0 68.8 1.4 1.0 8.2
114-2.10 8.7 10.0 6.0 8.0 0 1.3 0 0 4.0 2.3 56.3 0 0 3.3
115-1.50 10.7 13.9 23.7 6.0 0 4.0 0.3 0 0.9 1.3 36.8 0.9 0 1.6
115-2.50 11.4 10.8 13.3 2.2 0.3 4.0 0.3 0 2.2 1.1 45.4 2.8 0 6.2
115-3.00 11.5 9.0 8.7 7.4 0.6 1.5 0 0.3 4.3 1.5 44.3 5.9 0 5.3
115-4.25 8.2 23.1 3.8 6.0 0.3 1.3 0.3 0.4 2.2 2.8 34.8 8.8 0 8.2
115-4.75 4.0 19.0 7.7 6.6 0 2.2 0.4 0 0 1.7 36.4 8.4 0 13.2
Average 8.3 13.7 8.3 5.3 0.2 2.2 0.2 0.1 3.1 1.6 46.0 3.6 0.3 6.9
Table 11. Average composition (in % of the total sediment) of carbonate cap 1rocks
from seismic sequence FPF-1. (Moll = molluscs; Barn = barnacles;
Bry = bryozoans; Ech = echlnoids; Ost = ostracods; Bf = benthic foraminifers;
Pf = planktonic foraminifers; Alg = algae; Garb = unidentifiable carbonate
fragments; Spar = calclte cement; Mlc = microspar; Phos = phosphate;
0th = other authlgenlc minerals; Qtz = siliciclastic sand.)
DEPTH (M)
BELOW
SEDIMENT
SURFACE
PERCENT
Figure 11. Vertical distribution of major mlneraloglcal components In
FPF-1 (core OB-115).
84
The age of the carbonate cap on FPF-1 is controversial. I
interpret it to be Miocene for two reasons: 1) the contact between the
bioraicrosparite and underlying phosphorite in core OB-115 is gradational
over a vertical area of approximately 30cra, and 2) the same benthic
foramlniferal assemblage is present above and below the gradational
contact.
Figures 12 and 13 show the relative abundance and distribution of
the carbonate and siliciclastic components laterally within the FPF-1
seismic sequence, excluding the carbonate cap rocks on FPF-1. Carbonate
mud and fossils show an inverse relationship with siliciclastic sand and
insoluble mud. Notice that only the biomicrosparite cap on Frying Pan
phosphorites and the mlcrosparite along the 22m profile are really
carbonate sediments (contain more than 50% total carbonate).
Seismic unit FPF-2
Seismic unit FPF-2 was cored in several parts of Onslow Bay. The
Miocene section of core OB-110 located on the 22m profile in northern
Onslow Bay is a slightly fossiliferous (2.6%), muddy (22.6%), quartz
sand. Carbonate mud (2.1%) is present only as calclte. Bivalves (0.8%)
and echlnoids (0.4%) are the predominant fossils and are very well
preserved.
In central part of Onslow Bay (seismic profile 1-4) FPF-2 is a
quartz-rich (33.8%), mud. Calcareous fossils are present as less than
0.3% of the total sediment. Dolomite (15.5%) is present in the mud but
is not seen in the sand fraction. Sand-sized siliceous fossils
constitute 0.2% of the total sediment and are most likely more abundant
PERCENT
AREA
Figure 12 Lateral distribution, from north
(22m) Figure 13. Lateralto south (FP), of carbonate distribution, from north(22m) to
components in FPF-1. south (FP), of
slllclclastlc components in FPF-1. 00
Ln
86
in the mud fraction because most diatoms, radiolarians, and sponge
spicules are smaller than 63um. Chert nodules are also present in core
OB-47. A sharp decrease in siliceous fossils found in the sand-fraction
above chert nodules in OB-47 (Fig. 9) and supports the theory of a
biogenic silica source for chert nodule formation.
FPF-2 in the Frying Pan Area is a phosphatlc (2.4%), foraminiferal
(4.4%), quartz-rich (16.0%), mud. Calcite and dolomite are both present
as carbonate mud (11.8%). Another 0.3% of the total sediment is
composed of clinoptilollte as sand-sized internal molds of planktonic
and benthic foramlnifers. In cores OB-27, 63, and 70 (Plates 34 and 35)
clinoptilollte is present in almost all foraminiferal chambers.
Foraminifers are very well preserved in the bottom of core OB-27 but
have undergone increasing dissolution up-sectlon, until at the top of
the core foraminifers are nearly all destroyed and sediments are
dominated by internal molds (Fig. 14).
Total carbonate content in FPF-2 Increases slightly from northern
to southern Onslow Bay (Fig. 15). Insoluble mud also Increases from the
22m profile to the Frying Pan Area (Fig. 16) while slllciclastic sand
decreases. Calcareous fossils and carbonate mud show an inverse
relationship with each other (Fig. 15).
Seismic unit FPF-3
In central Onslow Bay FPF-3 is a sllghty phosphatlc (1.3%), sllghty
fossiliferous (6.0%), muddy (17.3%), quartz sand. Predominant fossils
include echinoids (1.1%), benthic foraminifers (1.0%), and barnacles
(0.7%). Carbonate mud (5.5%) consists of dolomite and calcite.
1.00 -
DEPTH (M)
3.00 -
BELOW
SEDIMENT
SURFACE 5.00 -
7.00 -
—I 1 1 \ 1 1 r-
0.0 2.0 4.0 6.0
PERCENT
Figure 14. Vertical distribution of zeolites and foramlnlfers In FPF-2
(core OB-27). 00
Figure 15 Lateral distribution, from north Figure 16 Lateral
(22m) distribution, from northto south (FP), of carbonate (22m) to south (FP), of
components in FPF-2. siliclclastic components in FPF-2
CO
00
89
FPF-3 in the Frying Pan Area is a mud containing very minor
phosphate (0.4%) and quartz sand (3.7%). Sand-sized radiolarians,
siliceous sponge spicules, and diatoms constitute 0.2% of the total
sediment. The mud is probably diatomaceous because abundant diatoms
were noted in thin section from core OB-17 at 3.00 m (Plate 9). Benthic
foraminifers (2.0%) are the predominant calcareous fossils and only
trace percentages of other fossils are present. The zeolite,
clinoptilolite, partially fills foraminiferal chambers. Carbonate mud
(18.7%) is present as dolomite or dolomite with calcite. In the one
thin section made of this lithology silt-sized dolomite rhombs
constitute 17.3% of the sediment. Dolomite in FPF-3 is pale yellow
compared to the clear dolomite in other sediments.
Total carbonate content in FPF-3 is about the same from seismic
profile 1-8 and the Frying Pan Area (Fig. 17). Calcareous fossils and
siliciclastic sands decrease while insoluble mud and carbonate mud
Increase from central to southern Onslow Bay (Figs. 17 and 18).
Seismic unit FPF-4
FPF-4, cored only in northern Onslow Bay along the 15m profile, has
an average composition of muddy (10.4%), fossillferous (23.3%), quartz
sand. Carbonate in the mud fraction is present only as calcite (4.1%).
The predominant fossils are bivalves (19.8%); barnacles (3.0%) are
secondary. All of the fossils are very well preserved.
Seismic unit FPF-5
FPF-5, cored along seismic profile 1-8, is a fossiliferous (19.3%),
muddy (20.5%), quartz sand. Carbonate mud (3.4%) is present but is not
AREA AREA
Figure 17. Lateral distribution, from north Figure 18. Lateral distribution, from north
(1-8) to south (FP), of carbonate (1-8) to south (FP), of vD
components in FPF-3. siliciclastic Ocomponents in FPF-3.
91
abundant enough to produce x-ray diffraction peaks. Predominant fossils
are barnacles (10.6%) and echinoids (2.3%). Dolomite (0.1%) is present
in the very fine sand and coarse silt fractions and can be seen
partially encased by syntaxial cement on echinoid fragments.
Along seismic profile 1-4, core OB-50 penetrated FPF-5, a
fossiliferous (12.0%), quartz-rich (30.0%), mud. Calcite and dolomite
are present in the mud fraction (17.0%). Molluscs (3.4%), barnacles
(3.0%), and echinoids (1.8%) are the major fossil components. Diatoms,
radlolarians, and siliceous sponge spicules are present in the bottom
part of the core. Zeolites are present in foraminiferal chambers at the
bottom of the core.
Total percent carbonate in FPF-5 increases slightly from seismic
profile 1-8 to 1-4 (Fig. 19). Fossils and siliclclastic sand both
decrease while both insoluble mud and carbonate mud increase from 1-8 to
1-4 (Figs. 19 and 20).
Seismic unit FPF-6
Along seismic profile 1-8 in central Onslow Bay, FPF-6 consists of
fossiliferous (26.4%), muddy (27.0%), quartz sand. Predominant fossils
are barnacles (11.3%), echinoids (5.9%), bivalves (2.1%), foraminlfers
(1.7%), and bryozoans (0.5%). Dolomite and calcite are both present in
the mud-sized carbonate fraction (20.0%).
In the Frying Pan Area, FPF-6 is a fossiliferous (31.2%), muddy
(31.6%), quartz sand. The mud-sized carbonate fraction (14.3%) is
composed of both calcite and dolomite. Predominant fossils Include
benthic foraminlfers (8.7%), echinoids (7.7%), and planktonic
1
PERCENT
AREA AREA
Figure 19. Lateral distribution, from north Figure 20. Lateral
(1-8) distribution, from northto south (1-4), of carbonate (1-8) to south (1-4), of
components in FPF-5. slllclclastic components in FPF-5.
93
foramlnlfers (6.1%) (Plate 6). Foramlnifers have partial internal molds
of loosely packed clinoptilolite crystals. Zeolites are present in the
center of echinoid spines, either replacing calcite or precipitating
within the spongy spine structure, in core OB-96 at 5.50 m. The more
poorly preserved the echinoid spines, the more zeolites are present.
Also in FPF-6 in the Frying Pan Area, core OB-102 has two beds of
echinoid-foraminiferal biosparite (Plate 11), lOcm and 5cm thick at 7.00
m and 7.75 m, respectively. Biosparite beds are in sharp contact with
the overlying and underlying sediment. Benthic foraminifers (31.2%),
planktonic foraminifers (22.2%), and echinoids (8.3%) are the
predominant fossils, with lesser abundances of molluscs (1.7%),
barnacles (1.5%), and ostracods (0.2%). Foramlnifers are unabraded and
unbroken, suggesting no transportion. These biosparites are well
cemented by syntaxial cement from the echinoids and radial rim cements
on the other fossils. Noncarbonate mud is sparse (6.0%), as is
microspar (0.5%).
Figures 21 and 22 show the lateral distribution of carbonate and
siliciclastic components in seismic unit FPF-6. Fossils and carbonate
mud show an inverse relationship as do siliciclastic sand and insoluble
mud. Total carbonate content remains almost constant.
Summary
The FPF sequence is predominated by siliciclastic sedimentation and
authigenic mineralization. Total carbonate content in each of the FPF
seismic units generally increases slightly toward the Frying Pan Area of
Onslow Bay (Fig. 23). Sharp variation of carbonate content of FPF-1
PERCENT PERCENT
AREA
Figure 21. Lateral distribution, from north Figure 22. Lateral distribution, from north
(1-8) to south (FP), of carbonate (1-8) to south (FP), of
components In FPF-6. sillclclastlc components In FPF-6.
95
CPAERBOCEANTET i3. Lateral distribution of carbonate components In each FPFseismic unit." 60 -CA 40 -PRBEORNCAETENT
1 1 1 1 1 n
FPF-1 FPF-2 FPF-3 FPF-4 FPF-5 FPF-6
SEISMIC UNIT
Figure 24. Average carbonate content of the FPF sequence
96
might reflect the carbonate cap was sampled along the 22m profile,
whereas along seismic profile 1-4 the basal siliclclastic facies was
sampled. Figure 24 shows the relative abundance of carbonate sediments
in each FPF seismic unit. Carbonate sediment decreases from FPF-1 to
FPF-2 but increases from FPF-2 to FPF-6. The overall lithology of FPF
seismic units contains less than 50% carbonate.
97
AF Sequence
The AF seismic sequence in Onslow Bay was deposited during the
Langhian (Moore, in prep.; Steinmetz in S.W.P Snyder, 1982). It ranges
in thickness from 0 m at its erosional updip truncation to over 250 m at
the edge of the continental shelf (S.W.P. Snyder, 1982). The AF
sequence thickens abruptly from 20 m to 40 m across an erosional scarp,
the White Oak Lineament, with over 25 meters of relief in northern
Onslow Bay (Fig. 6). Seismic data suggest that the AF sequence is
characterized by progradlng clinoforms, a pattern Indicating offshore
transportation and deposition of shelf edge sediments (S.W.P. Snyder,
1982).
Fourth-order seismic units that compose the AF sequence are labeled
AF-1 to AF-4 from oldest to youngest (Fig. 1). Sediments of the AF
sequence were cored only in northern and central Onslow Bay. Average
abundance of mineraloglcal and faunal components in each seismic unit
for all relevant seismic profiles (15m, 22m, 1-8, 1-4, and 1-5; see
Figure 8 for location map) are presented in Table 12. Average abundance
and distribution of major mineraloglcal components (carbonate,
phosphate, silica, siliciclastic sand, and mud) are summarized in Table
13. Tables 12 and 13 are compiled from reflected light microscopy and
Insoluble residue data (Appendices A and B).
Seismic unit AF-1
In northern Onslow Bay (along the 15m profile) AF-1 is a
quartz-rich (12.5%), fosslliferous (22.4%), carbonate mud. Total
carbonate content in this unit averages 55.5%. Only 0.1% of the total
Seismic Unit AF-1 AF-2 AF-3 AF-4
Profile 15m 22m 1-8 1-4 1-5 22m 1-5 15m 1-5 15m
if of Samples 6 4 5 3 2 2 2 2 3 14
Molluscs 2.4 tr 0.7 tr tr 2.7 tr 1.4 9.8 9.3
Barnacles 5.4 tr 0.1 tr tr 31.6 tr 24.4 5.7 32.4
Bryozoans 0.5 0 tr 0 0 0.2 0 0.6 1.5 4.6
Echlnolds 3.6 tr 0.1 0.3 tr 2.1 0.1 6.3 3.4 0.8
Ostracods 0.8 0 0 0 0 0 0 0.2 0 tr
B. Forams 3.1 tr tr tr tr 7.2 0 1.1 0.9 0.6
P. Forams 0.4 0 tr 0 0 2.5 0 0.4 0.1 0.1
Carbonate 6.2 tr 1.7 0.4 tr 8.8 tr 6.1 9.8 5.6
Spar tr 1.9 0.8 0.7 0.8 11.8 0 4.0 4.3 4.6
Dolomite 0.1 0.1 tr 0 0 0 0 tr 0 0.2
Chert tr 0.2 0 0 0 0 0 0 0 0
Diatoms 0.7 0 0 0 0 0 0 0 0 0
Radlolarla tr 0 0 0 0 0 0 0 0 0
Spicules tr 0 tr 0 0 0 0 0 0 tr
Skel Phos 0.2 0.4 0.1 0.5 tr 0.3 0.1 tr tr tr
Phosphate 0.2 0.6 0.3 1.8 0.5 0.4 0.1 0.5 0.1 0.1
Glauconite tr tr 0 0 0 0.2 0 tr 0 0
Opaques tr tr tr 0 0 0 0 0.1 0 tr
Other tr tr tr tr 0 0 0 0 0 0.1
Qtz Sand 12.5 54.7 61.6 68.0 91.7 16.2 48.6 22.1 33.2 1.2
Insol Mud 30.7 13.6 15.8 20.3 5.1 7.8 36.4 7.5 8.5 8.1
Carb Mud 33.0 28.4 18.5 7.8 1.8 8.2 14.7 25.4 22.7 32.3
TOTALS 99.8 99.9 99.7 99.8 99.9 100.0 100.0 100.1 100.0 100.0
Table 12. Summary of abundance and distribution of all mlneraloglcal and
faunal components (In % of total sediment) In the AF seismic units.
All numbers are based on reflected light microscopy and Insoluble
residue data (Appendices A and B). (Carbonate » unidentifiable
carbonate fragments; Spar = calclte cement; Qtz Sand - slllclclastlc
sand; Insol Mud = Insoluble mud; Carb Mud = carbonate mud.)
Seismic Unit AF-1 AF-2 AF-3 AF-4
Profile 15m 22m 1-8 1-4 1-5 22m 1-5 15m 1-5 15m
// of Samples 6 4 5 3 2 2 2 2 3 14
Fossils 22.4 tr 2.6 0.7 tr 55.1 0.1 40.5 31.2 53.4
CARBONATE Spar tr 1.9 0.8 0.7 0.8 11.8 0 4.0 4.3 4.6
CONSTITUENTS Dolomite 0.1 0.1 tr 0 0 0 0 tr 0 0.2
Carb Mud 33.0 28.4 18.5 7.8 1.8 8.2 14.7 25.4 22.7 32.3
Carbonate 55.5 30.4 21.9 9.2 2.6 75.1 14.8 69.9 58.2 90.5
Silica 0.7 0.2 tr 0 0 0 0 0 0 tr
MAJOR Phosphate 0.4 1.0 0.4 2.3 0.5 0.7 0.2 0.5 0.1 0.1
CONSTITUENTS Others tr tr tr tr 0 0.2 0 0.1 0 0.1
Qtz Sand 12.5 54.7 61.6 68.0 91.7 16.2 48.6 22.1 33.2 1.2
Insol Mud 30.7 13.6 15.8 20.3 5.1 7.8 36.4 7.5 8.5 8.1
TOTALS 99.8 99.9 99.7 99.8 99.9 100.0 100.0 100.1 100.0 100.0
Table 13. Summary from Table 12 of abundance and distribution of major
mlneraloglcal components (In % of total sediment) In AF seismic
units. (Spar = calclte cement; Qtz Sand = slllclclastlc sand;
Insol Mud = Insoluble mud; Garb Mud = carbonate mud.)
VO
100
sediment is sand-sized dolomite. Both calclte and dolomite are present
in the mud fraction (33.0%). A diverse assemblage of fossils including
barnacles (5.4%), echinoids (3.6%), foramlnifers (3.5%), molluscs
(2.4%), smooth and ornamented ostracods (0.8%), and bryozoans (0.5%) are
present (Plates 5 and 8). A small percentage of the fossils,
particularly some of the echinoids and barnacles, appear to be reworked.
Most echinoids are moderately well preserved, but a few are almost
totally covered by syntaxial cement overgrowths. Most barnacles are
also well preserved, but a small number are stained grey, have
glauconite- and pyrite-filled tubes, and display rounded edges.
Portions of seismic unit AF-1 (core OB-34) along the 15m profile
also contain a diverse assemblage of siliceous fossils including diatoms
(sand-sized specimens comprising 0.7% of the total sediment),
radlolarlans, and siliceous sponge spicules. Chert nodules, described
in the section on silicification, are also present in core OB-35.
Mild dissolution appears to have affected carbonate sediments of
AF-1 along the 15m profile. In reflected light, most calcareous fossils
are slightly leached. Dolomite is pitted and has a rough surface
texture.
AF-1 from the 22m profile is a muddy (42.0%), quartz sand. Fossils
are extremely scarce (less than 1% of the total sediment). Carbonate
mud (28.4%) occurs only as dolomite. Chert nodules are also present in
cores OB-38 and OB-40 and are described in the section on
silicification.
AF-1 along seismic profile 1-8 is a muddy (34.3%), quartz sand.
Calcareous sand is predominantly carbonate grains (1.7%), unidentifiable
101
d2u5e). to the fragmental and abraded nature of the grains. The predominateidentifiable fossils are molluscs (0.7%). Carbonate mud (18.5%) ispresent as either calclte or dolomite.In central Onslow Bay (seismic profile 1-4), AF-1 is a muddy(28.1%), quartz sand. Fossils are rare (0.7%). Carbonate mud (7.8%) ispresent only as dolomite; no dolomite occurs in the sand fraction.Along seismic profile 1-5, AF-1 is a slightly muddy (6.9%), quartzsand. Fossils are present in trace percents. Carbonate mud is rare(1.8%) and composed only of dolomite.The combined abundance of carbonate mud and calcareous fossils inseismic unit AF-1 decreases from northern to central Onslow Bay (Fig.Dolomite is present in the mud fraction in all but 3 samples of
AF-1. Sillciclastic sands and insoluble mud increase southward (Fig.
26).
Seismic unit AF-2
AF-2 is a muddy (16.0%), quartz-rich (16.2%), carbonate sand along
the 22m profile. Barnacles are the most abundant fossil group,
comprising 31.6% of the total sediment, with less abundant benthic and
planktonic foraminifers (9.7%), molluscs (2.7%), echinolds (2.1%), and
bryozoans (0.2%). Total carbonate content averages 75.1%. Carbonate in
the mud fraction (8.2%) consists of both calclte and dolomite.
Fossils and total carbonate content of unit AF-2 decrease toward
central Onslow Bay (Fig. 27) while sillciclastic sands and Insoluble mud
increase (Fig. 28). The southern facies of AF-2 is a quartz-rich
(48.6%), mud. Total carbonate content, mostly in the form of calclte or
AREA AREA
Figure 25. Lateral distribution, from north Figure 26. Lateral distribution, from north
(15m) to south (1-5), of (15m) to south (^1-5), of
carbonate components In AF-1. slllclclastlc 102components In AF-1.
PERCENT PERCENT
AREA AREA
Figure 27. Lateral distribution, from north Figure 28. Lateral distribution, from north
(22m) to south (1-5), of (22m) to south (1-5), of 103
carbonate components In AF-2. slllciclastic components in AF-2.
104
dolomite mud. Is only 14.8%.
Seismic unit AF-3
Seismic unit AF-3 in northern Onslow Bay (along the 15m profile) is
a quartz-rich (22.1%), muddy (32.9%), carbonate sand. Barnacles (24.4%)
and echinoids (6.3%) are the predominant fossils. Carbonate mud (25.4%)
is present as calclte with dolomite. Dolomite also occurs in trace
amounts as very fine sand-sized rhombs.
AF-3 in central Onslow Bay (along seismic profile 1-5) is a
quartz-rich (33.2%), muddy (31.2%), carbonate sand. Molluscs (9.8%) are
the predominant fossils with less abundant barnacles (5.7%) and
echinoids (3.4%). Carbonate mud (22.7%) is present as calclte with
dolomite at the top of core OB-131.
Fossils, carbonate mud, and total carbonate content decrease
slightly from the 15m profile to 1-5 (Fig. 29). Siliciclastic sands and
insoluble mud Increase slightly (Fig. 30).
Seismic unit AF-4
Seismic unit AF-4 was cored only along the 15m profile (northern
Onslow Bay). It is a muddy (40.4%), carbonate sand. Predominant
fossils are barnacles (32.4%), bivalves (9.3%), and bryozoans (4.6%).
Echinoids, benthic and planktonic foramlnifers, and ostracods each
average less than 1% of the total sediment. A small percentage of the
barnacles appear to be reworked; they are rounded, stained grey, and
have pyrite or glauconite in pore spaces.
Dolomite (0.2% of the total sediment) occurs in the very fine sand
fraction and in the mud fraction as euhedral, silt-sized crystals that
60-
PERCENT 40 PERCENT 40 -
• — £AR80_nate mud
—•
20 20
INSOLUBLE MUD
•
~r
1 5m T"1-5 1 5m 1-5
AREA AREA
Figure 29. Lateral distribution, from north Figure 30. Lateral(15m) to south (1-5), of distribution, from north
carbonate (15m) to southcomponents in AF-3. (1-5), ofslliclclastlc 105components In AF-3.
Figure 31. Lateral distribution of carbonate Figure 32. Average carbonate content of the
components in each AF seismic unit. AF sequence. 107
108
BBF Sequence
The BBF sequence was deposited during the Serravalllan (S.W.
Snyder, unpub. data; Stelnmetz, unpub. data). In Onslow Bay It ranges
from 0 m at Is eroslonal updlp truncation to more than 200 m In
subsurface (S.W.P. Snyder, 1982). The BBF seismic sequence Is divided
Into 6 fourth-order units labeled BBF-1 to BBF-6 from oldest to youngest
(Fig. 1). Seismic unit BBF-1 may actually be a composite of several
seismic units (S.W.P. Snyder, 1982). Riggs and others (1985) subdivided
BBF-1 into 5 lithologic units based upon patterns of the major
mineralogical components.
The BBF sequence crops out only in northern and central Onslow Bay
where it is predominantly sillclclastic sediments. Seismic units BBF-4
and BBF-5 were not vibracored. The average abundance of mineralogical
and faunal components in each seismic unit for each area of Onslow Bay
(15m profile; 22m profile; profiles 1-8, 1-4, and 1-5; see Figure 8 for
location map) are presented in Table 14. Table 15 summarizes the
average abundance and distribution of major mineralogical components
(carbonate, phosphate, silica, sillclclastic sand, and mud). Tables 14
and 15 are compiled from reflected light microscopy and Insoluble
residue data (Appendices A and B).
Seismic unit BBF-1
BBF-1 is the most thoroughly sampled of the BBF seismic units. It
crops out in northern and central Onslow Bay. Nine samples in cores
from the 15m profile revealed two lithologies. The lower one (Lithology
I), from cores 0B-2B, 3, and 36, Is a muddy (43.9%), quartz-rich
Seismic Unit BBF-1 BBF-2 BBF-3 BBF-6
Profile 15m 22m 1-4 1-5 1-4 22m 15m
Lithology # I II I II III I II I II
# Samples 5 4 4 2 3 1 6 1 1 2 3 6
Molluscs 0.1 tr tr 1.9 0.2 0.1 0.5 3.8 tr 0.2 0.5 0.1
Barnacles 0 0 tr 7.7 0.1 tr 1.4 0.7 tr tr 11.5 tr
Bryozoans 0 0 0 0 0 tr tr tr 0 0 0.1 0
Echlnolds tr tr 0 1.5 0.2 0 0.2 0.4 0.6 0.1 0.7 0.4
Ostracods 0 0 0 0.1 0 0 tr 0.1 tr 0 tr 0
B. Forams tr 0.6 0 2.9 0.3 0 0.2 1.0 0.6 tr 1.6 1.2
P. Forams 0 0 0 0 0 0 0 0 0.1 0 0.1 0
Carbonate tr tr tr 0.2 0.1 0 0.3 0.2 6.0 0.6 3.0 0.3
Spar 0.5 0 0 0 0.1 0.1 0.2 tr 2.9 0.4 5.0 tr
Dolomite 0 0.5 0 0.1 tr 0 0 0 0 0 0 1.0
Chert 0 0 0 0 0 0 0 0 0 0 0 0
Diatoms 0 0 0 0.1 0 0 tr 0 0 0 0 0
Radlolarla 0 0 0 0 0 0 0 0 0 0 0 0
Spicules 0 0 0 0 0 0 0 0 0 0 0 0
Skel Phos 3.9 1.8 0.8 1.5 2.8 0.1 2.3 0.6 0.2 tr 0.2 2.8
Phosphate 9.1 4.1 2.3 1.5 3.7 tr 8.4 0.5 tr tr tr 6.6
Glauconite 0 1.0 tr 0.1 0.1 0 0.1 0.3 0 0 tr 0.1
Opaques 0 0 0 0 0 tr tr 0 0 tr 0 tr
Other 0 0 0 0 0 0 tr 0.3 tr 0 0 tr
Qtz Sand 43.9 66.3 49.3 28.0 63.0 7.4 49.9 72.7 6.1 88.7 19.9 62.0
Insol Mud 39.9 17.8 43.4 25.9 23.6 45.9 25.8 12.2 61.4 4.6 29.0 12.2
Carb Mud 2.8 7.9 4.3 28.5 5.7 46.3 10.7 7.1 22.0 5.4 28.4 13.3
TOTALS 100.2 100.0 100.1 100.0 99.9 99.9 99.8 99.9 99.9 100.0 100.0 99.9
Table 14. Summary of abundance and distribution of all mlneralogical and faunal
components (In % of total sediment) In the BBF seismic units. All
numbers are based on reflected light microscopy and Insoluble residue
data (Appendices A and B). (Carbonate == unidentifiable carbonate 109
fragments; Spar » calclte cement; Qtz Sand ~ slllclclastlc sand;
Insol Mud Insoluble mud; Carb Mud ° carbonate mud.)
Seismic Unit BBF-] BBF-2 BBF-3 BBF-6
Profile 15m 22m 1-4 1-5 1-4 22m 15m
Lithology it I 11 I II III I II I II
it of Samples 5 4 4 2 3 1 6 1 1 2 3 6
Fossils 0.1 0.6 tr 14.0 0.9 0.1 2.7 6.6 7.3 1.0 17.5 2.0
CARBONATE Spar 0.5 0 0 0 0.1 0.1 0.2 tr 2.9 0.4 5.0 tr
CONSTITUENTS Dolomite 0 0.5 0 0.1 tr 0 0 0 0 0 0 1.0
Carb Mud 2.8 7.9 4.3 28.5 5.7 46.3 10.7 7.1 22.0 5.4 28.4 13.3
Carbonate 3.4 9.0 4.3 42.6 6.7 46.5 13.6 13.7 32.2 6.8 50.9 16.3
Silica 0 0 . 0 0.1 0 0 tr 0 0 0 0 0
MAJOR Phosphate 13.0 5.9 3.1 3.0 6.5 0.1 10.7 1.1 0.2 tr 0.2 9.4
CONSTITUENTS Others 0 1.0 tr 0.1 0.1 tr 0.1 0.6 tr tr 0 0.1
Qtz Sand 43.9 66.3 49.3 28.0 63.0 7.4 49.9 72.7 6.1 88.7 19.9 62.0
Insol Mud 39.9 17.8 43.4 25.9 23.6 45.9 25.8 12.2 61.4 4.6 29.0 12.2
TOTALS 100.2 100.0 100.1 99.7 99.9 99.9 100.1 100.3 99.9 100.1 100.0 100.0
Table 15. Summary from Table 14 of abundance and distribution of major
mlneraloglcal components (In % of total sediment) In BBF seismic
units. (Spar = calclte cement; Qtz Sand = slllclclastlc sand;
Insol Mud = Insoluble mud; Garb Mud = carbonate mud.)
o
Ill
(46.4%), phosphorite sand. Phosphate grains (11.1%) are predominantly
intraclastic and pelletai. The only fossils present are bivalves
(0.1%), and traces of echinolds and benthic foramlnifers. Carbonate mud
(2.8%) is too rare for it's mineralogy to be determined by x-ray
diffractometry. The upper lithology (Lithology II), present in cores
OB-2 and OB-91, is a phosphatlc (5.9%), muddy (23.7%), quartz sand.
Benthic foraminlfers are slightly more abundant (0.6%), with trace
percentages of bivalves and echinoids. Dolomite is present in the fine
sand fraction (0.5%) and in the carbonate mud fraction (7.9%) mixed with
calcite.
Along the 22m profile, three BBF-1 lithologies were sampled. The
lowermost lithology (Lithology I), from cores OB-6 and OB-39, is a muddy
(47.7%), quartz sand. Fossils consist of trace percentages of bivalves
and barnacles. Carbonate mud (4.3%) is a minor constituent and it's
mineralogy could not be identified by x-ray diffractometry. Lithology
II occurs in core OB-71 and at the bottom of OB-109. It is a
fossiliferous (14.0%), quartz-rich (28.0%), mud. Carbonate mud (28.5%)
consists of both calcite and dolomite. Fossils include barnacles
(7.7%), benthic foraminlfers (2.9%), bivalves (1.9%), echinoids (1.5%),
and ostracods (0.1%). The uppermost lithology (Lithology III), found in
the upper three samples of core OB-109, is a phosphatlc (6.5%), muddy
(29.3%), quartz sand. Fossils average 0.9% of the total sediment and
include benthic foraminlfers, echinoids, bivalves, and barnacles.
Carbonate mud (5.7%) is also present. Dolomite was identified on only
one of the three x-ray diffractograms.
Two lithologies were sampled in BBF-1 along seismic profile 1-4.
The lowermost lithology (Lithology I), present in core OB-52, is a
quartz-rich (7.3%), dolomitic (46.3%) mud. Fossils are almost
nonexistent (0.1%). Dolomite is present only in the mud fraction.
The upper BBF-1 lithology (Lithology II), from cores OB-53 and
OB-60, is a muddy (36.5%), quartz-rich (49.9%), phosphorite sand.
Carbonate mud (10.7%) is present as calcite. Fossils consist of
barnacles (1.4%), bivalves (0.5%), echinoids (0.2%), benthic
foraminlfers (0.2%), and trace percentages of bryozoans and ostracods.
Three l-3cm thick laminae of moldic microsparite are present in cores
OB-53 and OB-60. Laminae are phosphatic (4.1%), quartz-rich (13.6%),
and in sharp contact with the overlying and underlying sediment. The
first stage of cementation was growth of isopachous cement within
intraparticle pore spaces in barnacle plates. Neomorphism of micrlte to
microspar fully cemented the sediment. Later, dissolution of mollusc
fragments produced secondary moldic porosity, which was then partially
occluded by blocky pore filling cement.
Two samples from the BBF-1 section of core OB-59, located on
seismic profile 1-5, have very different lithologies. The
stratigraphically lower lithology (Lithology I) is a slightly
fossiliferous (6.6%), muddy (19.3%), quartz sand. Carbonate mud (7.1%)
consists of a mixture of calcite and dolomite. Predominant fossils are
bivalves (3.8%) and benthic foraminlfers (1.0%). The upper lithology
(Lithology II) is a quartz-rich (6.1%), slightly fossiliferous (7.3%),
mud. Most fossils (6.0%) are unidentifiable because of fragmentation
and extensive growth of calcite cementi Echinoids (0.6%) and benthic
foraminlfers (0.6%) are the predominant identifiable fossils. Both
113
calcita and dolomite are present in the carbonate mud (22.0%).
Figures 33 and 34 show carbonate and siliciclastic components in
seismic unit BBF-1. These graphs show that: 1) all BBF-1 sediments are
siliciclastic; 2) carbonate content of BBF-1 increases from northern to
central Onslow Bay; 3) relative carbonate content increases upsectlon in
most seismic profiles; and 4) most carbonate in BBF-1 is found in the
mud fraction.
Seismic unit BBF-2
Unit BBF-2 was cored only in central Onslow Bay along seismic line
1-4 (core OB-92). A calcite cemented sandstone occurs at the top of the
Miocene section in this core. Calcite cementation decreases down
section, accompanied by a corresponding increase in quartz sand (Fig.
35). A small percentage of the components are insoluble clay and
fossils, which consist of barnacles, bivalves, and echinoids. The
fossils decrease slightly in concentration down section, with a
corresponding increase in clays.
Initial cementation was by interparticle and intraparticle
Isopachous cement on fossils. Second generation calcite cements are
drusy and blocky pore filling cements. Drusy cement is gradational with
isopachous cement, filling in remaining intraparticle pore space and
sheltered areas between fossils. Blocky pore filling cement, which
fills in the remaining Interparticle pore spaces, is the most abundant
type. Crystal size increases from grain surfaces into pore spaces,
grading into patches of microspar. Later dissolution of a few large
molluscs left molds which are not filled in by a second stage of pore
60 -
PERCENT
AREA AREA
Figure 33. Lateral distribution, from north Figure 34. Lateral distribution, from north
(15m) to south (1-5), of (15m) to south (1-5), of
carbonate components in BBF-1. sillclclastlc and phosphatlc 114
components in BBF-1.
3.00 -
3.50
DEPTH (M)
BELOW
4.00
SEDIMENT
SURFACE
4.50 \
5.00 \
T 1 r- “I r-
0 20 40 60 80 100
PERCENT
Figure 35. Vertical distribution of carbonate and slllclclastlc
components In BBF-2 (core OB-92). The Miocene portion 115
of this core begins at 3.00 meters.
116
filling cement.
Seismic unit BBF-3
BBF-3, cored only along the 22m profile (core OB-108), is a
fossiliferous (17.5%), quartz-rich (19.9%), mud. Both calcite and
dolomite are present in the mud fraction (28.4%). Predominant fossils
are barnacles (11.5%) and benthic foraminifers (1.6%). Total carbonate
content averages 50.9%.
Two 20cm thick beds of quartz-rich (29.5%), moldic biomicrosparite
are present at the top of the Miocene section in core OB-108 and are in
sharp contact with the surrounding unlithified sediment. The first
stage of cementation is an isopachous cement lining interparticle and
intraparticle pore spaces around fossils. Second generation drusy and
blocky pore filling cement partially filled remaining intraparticle pore
spaces, and ralcrlte neoraorphosed to raicrospar, filling in remaining
Interparticle pore space. Later dissolution of mollusc fragments left
secondary moldic porosity which remained unfilled.
Seismic unit BBF-6
BBF-6 crops out only in northern Onslow Bay and was cored along the
15m profile. Here it is a phosphatic (9.4%), muddy (25.5%), quartz
sand. Total carbonate content averages 16.3%. Benthic foraminifers
(1.2%) and echinoids (0.4%) are the predominant fossils. Carbonate mud
(13.3%) occurs as both calcite and dolomite. Dolomite (1.0%) also is
present in the fine and very fine sand fractions, but it shows no
stratigraphic trend
117
DISCUSSION
Four patterns of carbonate sedimentation are present in the Fungo
River Formation in Onslow Bay: 1) cyclic carbonate sediments overlying
noncarbonate lithologies and deposited as a couplet during the same
sea-level cycle; 2) barnacle-rich, relatively pure carbonate sediments
deposited throughout each fourth-order sea-level cycle of the AF seismic
sequence; 3) sparse fossils and minor carbonate mud disseminated in
noncarbonate lithologies; and 4) thin carbonate laminae interbedded with
noncarbonate lithologies.
Cyclic Patterns of Carbonate Sedimentation
Carbonate sediments gradationally overlie siliciclastics and other
lithologies. Each gradational noncarbonate-carbonate sediment sequence
was deposited during one fourth-order sea-level cycle. Carbonate
sediments in the Fungo River Formation in Onslow Bay include: 1) those
that fit the Idealized cycle of Riggs (1984), and 2) barnacle-rich
carbonates associated with hardgrounds.
Carbonates Associated with the Idealized Cycle of Riggs
Riggs (1984) proposed a model to explain the origin, distribution,
and cyclic nature of Neogene sediments on the southeastern U.S. Atlantic
continental margin. Major climatic changes cause multiple cycles of
glaciation and déglaciation, and resulting sea-level fluctuations, along
with climate, control sedimentation. During glacial maxima, semi-arid
conditions result in sparse vegetation and streams carry large sediment
loads. As climate becomes warmer and more humid, vegetation Increases
and sediment load decreases in streams carrying finer siliciclastic
materials. With rising sea level, the Gulf Stream moves towards and
begins to interact with the continental shelf. Upwelling occurs where
bathymetric contours diverge on the downstream side of topographic and
structural highs which interact with the Gulf Stream. Cold upwelling
waters supply nutrients for organic production and subsequent phosphate
mineralization. Carbonates are produced during glacial minima and
sea-level maxima when warm Gulf Stream waters flow across the
continental shelf.
Theoretically, each Pungo River seismic unit in Onslow Bay is a
product of a sea—level cycle and should consist of an idealized cyclical
sediment sequence (siliciclastic sediment at the base, increasing
phosphate and associated authigenlc sediments up section, culminating in
carbonates) or some variation on this theme (Riggs, 1984). However,
erosional processes during each lowstand may have locally removed part
or all of any preceding sediment sequence. Where preserved, the upper
carbonates should be most extensively affected by dlagenesis and the
degree of diagenesls should decrease down section. This model is
summarized in Table 16. This model is documented by sediments in Onslow
Bay where the cap rocks are of several different carbonate lithologies.
One distinct lithology occurs in seismic unit FPF-1 in the Frying
Pan Area (cores OB-20, 64, and 115). The age of these cap rocks is
controversial, as discussed in the description of FPF-1. Carbonates are
biomlcrosparltes which overlie and grade into phosphorite sands (Fig.
11). They contain a diverse fossil assemblage consisting of barnacles,
bryozoans, bivalves, echinolds, benthic and planktonic foramlnifers,
Sea-level Climate, Fauna, Gulf Stream (GS) Sedimentation Patterns
Associated with: and Vegetation Dynamics and Processes
early-mid stage moderating climate; GS migrates west; fine-grained terrigenous sediment
transgression cool water fauna; topographic upwelling deposited on inner part of shelf;
Increasing vegetation and frontal eddies phosphate deposited around nose of
begin topographic feature; carbonate inter-
bedded with phosphate on outer shelf
mid-late stage moderating climate GS continues west- phosphate sedimentation increases and
transgression ward migration; migrates further onto shelf;
upwelling increases terrigenous sedimentation decreases;
carbonates limited to outer shelf
sea-level interglacial; upper portion of GS carbonate deposltlonal regime;
maximum warm, humid climate; spills onto shelf reworking of previously deposited
heavy vegetation; phosphates; terrigenous sedimentation
subtropical fauna reduced to a minimum
sea-level glacial maximum; GS forced eastward erosion of previously deposited
minimum cold, semi-arid; sediments; nondeposition and exposure
decreased vegetation diagenetically alters sediments;
increase in terrigenous sedimentation
beginning of thick phosphorite pavements form;
oceanic overturn these are torn up to produce
intraclast pebbles which dominate
the lower facies of each cycle
119
Table 16 Neogene sedimentation model for the southeastern ted States (Riggs, 1984)
120
ostracods, coralline algae, decapods, serpulld worms, and coralline and
dasycladacean algae. This abundant and diverse fauna and flora indicate
open shelf conditions and warm temperate to subtropical waters.
Waters (1983) found that phosphorites in FPF-1 are predominated by
benthic foramlniferal taxa indicative of mid to outer shelf,
nutrient-rich, oxygen-poor conditions produced by upwelling. The
phosphorites grade upward into, warm water assemblages of the carbonate
cap rocks. These carbonates appear to mark the end of a fourth-order
sea-level transgression when warm Gulf Stream waters flooded the
continental shelf.
A second carbonate lithology forms the cap rock of seismic unit
BBF-2 (core OB-92). It is actually a slightly fossiliferous (4.3%),
calcite cemented (41.4%), quartz sandstone (total carbonate content of
45.7%) which grades downward into an unlndurated quartz sand with 1.9%
carbonate (Fig. 34). The upper part of the section has undergone
cementation by blocky pore filling cement and dissolution of bivalves.
This type of carbonate cap rock also fits Riggs’ (1984) model of Neogene
sedimentation because both carbonate content and diagenesis decrease
down section.
Barnacle-rich Carbonates
A third lithology, consisting of barnacle-rich carbonate sediments,
occurs as an upper facies in the depositlonal sequence. These appear to
be regional developments that represent a variation on the idealized
cycle of Riggs (1984). Discussion of these barnacle-rich carbonates in
the Pungo River Formation in Onslow Bay must begin with a brief
121
consideration of their ecology.
Barnacle Ecology. Pungo River barnacles are true barnacles belonging
to Order Thoracica in the Class Crustacea, Subclass Cirrlpedia.
Barnacles present in the Pungo River Formation in Onslow Bay are all
balanomorphs and include Megabalanus sp. in the BBF sequence, Balanus
imitator in the AF sequence and seismic units FPF-3 through FPF-6, and
an unidentified form (similar to Balanus amphitrites present in the
Pleistocene Wacamaw Formation) in FPF-1 (V.A. Zullo, pers. comm.). The
majority of the the barnacles in FPF-1 appear to be reworked; they are
fragmented, have rounded edges, and are stained grey. Barnacles in the
BBF sequence are a warmer water taxa than those in FPF and AF sequences
(Zullo, pers. comm.). This correlates well with the sea-level curve of
Vail and Mitchum (1979) which shows a sea-level maximum during the
Serravalllan (Fig. 5).
The shells of balanoraorph barnacles consist of 12 plates, eight
outer compartmental plates attached to a basal disc, and four inner
opercular plates (Newman and others, 1969; Zullo, 1979), composed of
low-Mg calcite (Milliman, 1974). Barnacles are eplbenthic filter
feeders that require a hard substrate for attachment. They are most
common in the intertidal zone which is best suited for their filter
feeding lifestyle, but they do occur in neritic waters where there are
ample currents. They can live in many marine environments but are more
abundant in subtropical to temperate waters. Growth of barnacles is
faster in warmer waters; however, they are not common on tropical
shelves (Milliman, 1974) possibly due to grazing fish that scrape the
122
substrate and remove barnacle larvae (Newman, 1960) or to competition
with corals which predominate the epibenthlc fauna. In Woods Hole,
Massachusetts and Monterey Bay, California the life span of balanomorph
barnacles is only about a year (Grave, 1933; Smith and Haederbie, 1969).
Shell accretion is rapid, 15 to 30 mm/year (Pequegnat and Fredericks,
1967; Smith and Haederbie, 1969). Because barnales are short lived,
gregarious organisms that produce 12 relatively large calclte plates per
individual, their disarticulated plates are an important carbonate
component of sediments in subtropical and temperate environments.
Barnacles, though present since the Silurian (Newman and others,
1969), have been common sediment components only since the Cretaceous.
Wilson (1975) and Flugel (1982) did not include barnacles in their
standard carbonate mlcrofacles, perhaps because very little
paleoecological work has been done them. Therefore, barnacles are
generally considered less useful for paleoecological Interpretations
than many other fossil groups.
Inner Shelf Deposits. Barnacle-rich carbonates which cap seismic
units FPF-5 and FPF-6 (cores OB-45 and OB-46) are unindurated and
consist of abundant (29.5%) barnacle plates, with lesser abundances of
echinoids (6.3%) and benthic foramlnifers (2.2%). Carbonate mud
(34.6%), quartz sand (7.0%), and Insoluble matrix (6.8%) are other major
components present in these sediments. Total carbonate content averages
86.3% of the total sediment. Barnacles are well preserved and appear to
have undergone little transportion.
Carbonates similar to those in FPF-5 and FPF-6 occur in seismic
123
units BBF-1 and BBF-3 (in the base of core OB-109 and throughout the
Miocene section in core OB-108, respectively). Barnacles (12.4%) are
less abundant and occur with benthic foraminifers (2.4%), molluscs
(1.3%), and echinoids (1.2%). Quartz sand (21.6%) and insoluble matrix
(26.8%) are higher than in the FPF barnacle-rich sediments while
carbonate mud content is lower (27.1%). Total carbonate content
averages 50.8% of the total sediment. Barnacle-rich carbonates in core
OB-109 are at the base of the core and could represent the end of a
fourth-order sea—level cycle because: 1) sediments in cores
stratigraphlcally lower in BBF-1 are siliclclastics, 2) sediments in the
upper part of core OB-109 are siliclclastics, and 3) BBF-1 may actually
contain three selsmic/llthologic units (S.W.P. Snyder and others, 1983;
Riggs and others, 1985). The composition of barnacle cap rocks in the
Pungo River Formation in Onslow Bay is summarized in Table 17.
Riggs' (1984) model can be related to the presence and distribution
of barnacle beds which overlie siliclclastic sediments in the Pungo
River Formation. Regression during fourth-order eustatic sea-level
cycles results in submarine or subaerial exposure of previously
deposited sediments and formation of hardgrounds. Barnacles attach to
these hardgrounds on the inner shelf. If there is an adequate sediment
supply, rising sea level buries the barnacles, which remain articulated
and attached to the hardground, during the next transgressive cycle
(Fig. 36). Such a senario can be observed on top of seismic unit FPF-1
(core OB-132).
During a regression, barnacles growing on hardgrounds are
disarticulated by current action and accumulate on top of sediments
Sample Moll Barn Bry Ech Ost Bf Pf Garb Spar Dolo Phos 0th Qtz Matr
FPF-6
45-1.00 0.5 27.5 0.5 5.6 0.0 1.7 0.1 9.8 0.0 0.2 0.5 0.0 8.7 44.9
FPF-5
46-0.75 0.6 31.6 0.5 6.9 0.1 2.6 0.3 14.8 0.0 0.2 0.1 0.2 5.2 36.9
BBF-3
108-2.75 0.4 6.6 0.2 0.4 0.1 1.7 0.0 1.8 tr 0.0 0.2 tr 10.9 77.8
108-3.7 0.7 18.7 0.1 1.0 0.0 1.3 0.0 5.0 5.8 0.0 0.3 0.0 27.6 39.5
108-5.00 0.3 9.3 0.1 0.6 0.0 1.7 0.2 2.2 9.3 0.0 0.2 0.0 21.2 54.9
BBF-1
109-5.75 3.8 15.3 0.0 2.8 0.2 4.9 0.0 0.4 0.0 0.0 2.7 0.1 26.6 43.2
Table 17. Composition of barnacle cap rocks. (Sample = core-depth (m); Moll = molluscs;
Barn = barnacles; Bry = bryozoans; Ech = echlnolds; Bf = benthic foramlnifers;
Pf = planktonic foramlnifers; Garb = unidentifiable carbonate fragments;
Spar = calclte cement; Dolo = dolomite; Phos = phosphate; 0th = other
authlgenlc minerals; Qtz = slllclclastlc sand; Matr = matrix.)
124
125
A
B
Figure 36. Deposition and preservation of barnacles during a
transgression. A. Barnacles (triangles) grow on
hardgrounds formed on top of sediments deposited during
previous sea-level cycles (fine stipple pattern). B. With
rising sea-level, sediments deposited during the current
fourth-order cycle (coarse stipple pattern) bury the
barnacles articulated and attached to the hardground.
126
which were deposited during the previous transgression (Fig. 37). If
barnacles continue to establish themselves down the shelf at the rate of
regression, an extensive layer of disarticulated barnacle plates will
overlie much of the previously deposited sediment. If the barnacles can
not keep up with the regression, then localized zones of plates will
occur nearshore but will be absent further offshore. Disarticulated
barnacles occur as cap rocks on noncarbonate lithologies in seismic
units FPF-5, FPF-6, BBF-1, and BBF-3 (cores OB-46, OB-45, OB-109, and
OB-108, respectively). I believe these carbonates represent the
regressive phase of their respective deposltlonal cycles.
Outer Shelf-Slope Deposits. The AF third-order seismic sequence is
the only one which is predominanted by carbonate sedimentation (greater
than 50% carbonate) through each fourth-order seismic unit. Average
carbonate content Increases up section and toward northern Onslow Bay
(Fig. 23).
Seismic unit AF-1 is a quartz-rich (12.5%), fosslliferous (22.4%),
carbonate mud in northern Onslow Bay (the 15m profile). It contains a
diverse assemblage of calcareous and siliceous fossils Including
barnacles, echinoids, benthic and planktonic foraminifers, molluscs,
ostracods, bryozoans, diatoms, radiolarians, and siliceous sponge
spicules. All diatoms seen in the sand fraction are centrics (round),
the majority of which are planktonic. Low individual abundances and
high diversity of organisms in AF-1 indicates deposition on an open
shelf, probably mid to outer shelf based on the abundance of planktonic
foraminifers, centric diatoms, and radiolarians.
127
Figure 37. Deposition and preservation of barnacles during a
regression. A. Barnacles (triangles) grow on hardgrounds
formed on top of sediments deposited during the current
fourth-order sea-level cycle (coarse stipple pattern). B.
Current activity caused by regression disarticulates
barnacles and scatter their plates (dashed line) over
sediment deposited during the current fourth-order cycle.
Seismic units AF-2 and AF-3 contain similar quartz-rich, muddy
carbonate sands in northern Onslow Bay (Table 13). Barnacles constitute
more than 24% of the sediment. Echlnoids, foraminifers, and molluscs
contribute another 9-15% to the sands (Table 14). Other fossils are
relatively rare (less than 1%). Unit AF-3 also is a quartz-rich, muddy
carbonate sand in central Onslow Bay; however, barnacles are not as
abundant (5.7%), and molluscs (9.8%), echlnoids (3.4%), and bryozoans
(1.5%) are more abundant. More than 80% of the fossils in AF-2 and AF-3
are poorly preserved. Barnacles, molluscs, and bryozoans are stained
grey and have bored and abraded surfaces. Borings are often filled with
glauconite or pyrite. Most echlnoids are overgrown by calcite cement.
Many of the more coarsely perforate foraminifers are covered by a thin
coat of calcite cement. Few moderately to well preserved echlnoid
fragments and planktonic and benthic foraminifers are present. Poorly
preserved fossils are Interpreted as transported and probably reworked,
while well preserved specimens probably accumulated during that
particular sea-level cycle. Open shelf conditions are indicated by this
assemblage of fossils; however, the majority appear to be reworked.
Benthic foraminifers of AF-3 in central Onslow Bay Indicate a mid to
outer shelf environment (Moore, in prep.).
Seismic unit AF-4 is a muddy (40.4%), carbonate sand. Most of the
mud is carbonate (Table 12). Barnacles are the predominant fossils,
with less abundant bivalves and bryozoans. Some of the barnacles appear
to have been transported or possibly recycled from older sediment
sequences. These barnacles have rounded edges and abraded surface
ornamentation, are stained light grey, and contain borings often filled
129
with glauconite or pyrite. The percentage of stained and rounded
barnacles increases upward from about 5% at the base to about 40% at the
top of AF-4. Remaining barnacles lack stain, and exhibit only minor
rounding of edges and little destruction of surface ornamentation. AF-4
sediments differ from other barnacle-rich Fungo River sediments in
Onslow Bay because of the abundance of bryozoans. Echinoids are a
relatively minor component in AF-4, but constitute a larger percentage
of other barnacle-rich sediments.
Milliraan (1974) found that the major epibenthic carbonate producers
on the modern continental shelf of the eastern United States and Canada
are barnacles. Most are associated with the algal ridge system and
other rocky areas at the shelf break. Barnacle-rich sediments are rare
on most other shelves, with the exception of the coast of Ireland,
Alaska, and eastern Africa. Bryozoans and coralline algae are the
predominant epibenthic fauna and flora on remaining non-tropical shelves
(Milliman, 1974, 1977).
S.W.P. Snyder (1982) interpreted the White Oak Lineament as the
paleo-shelf edge during the Langhian. All AF seismic units appear to
have been deposited over the White Oak Lineament as a series of
prograding clinoforms; the same type of seismic pattern occurs in modern
sediments being deposited on the slope beyond the shelf break (A.C.
Mine, pers. comm.). Sediments in AF-4 dip more steeply than those in
AF-1, AF-2, or AF-3 (Fig. 7).
The greater predominance of barnacles, with lesser abundances of
bivalves and bryozoans, in seismic unit AF-4 indicates deposition under
conditions different from those of AF-1 through AF-3. AF-4
130
barnacle-rich sediments probably formed on hardgrounds along the shelf
edge, were disarticulated, and redeposlted as clinoform beds over the
shelf break.
Carbonates in Noncarbonate Lithologies
Disseminated Carbonates
Some calcareous fossils and carbonate mud are present in nearly all
noncarbonate lithologies examined. The most common fossils in
noncarbonate lithologies are echinoids, bivalves, and benthic
foraminlfers, all calcareous organisms that lived in a predominantly
siliciclastic marine environment. Barnacles, bryozoans, and ostracods
are relatively rare in noncarbonate lithologies.
Siliceous fossils are often present in very fined grained
siliciclastic sediments where calcareous fossils are rare to absent
(Figs. 38 and 39). The only exception to this is in core OB-34 (seismic
unit AF-1) where a diverse assemblage of both calcareous and siliceous
fossils are present in the sand.
The source of most carbonate mud in "normal" carbonate environments
is from disarticulation of green algae (l.e., Penicillus) which
contribute aragonite needles to the sediment. Green algae that
contribute carbonate to the sand fraction in subtropical to tropical
carbonate environments include dasycladaceans and the codiacean algae
Halimeda. Dasycladacean algae occurs in only trace percentages in the
carbonate cap rocks of FPF-1. Molnia and Pllkey (1972) and Crowson
(1980) stated that most modern carbonate mud in Onslow Bay is derived
from bio-mechanical degradation of larger carbonate grains. This also
100 • •
90
FCOALS 80- • •CASREILOUSS MATRIX 70-% 60-
50-
I I I
0.5 1.0 1.5 2.0 2.5
% SILICEOUS FOSSILS % SILICEOUS FOSSILS
Figure 38. Sand-size siliceous vs. calcareous Figure 39. Sand-size siliceous fossils vs.
fossils shoving the predominance matrix showing the predominance
of siliceous fossils where of siliceous fossils In very 131
calcareous fossils are rare. muddy sediments.
132
is the most likely source for most calclte mud in the Pungo River
Formation in Onslow Bay, especially in sediments that are predominantly
muds with a high insoluble content. Loaf-shaped, 10-30um calclte
crystals, which Folk (1965) calls psuedospar, were seen in thin sections
of muds from seismic unit FPF-2. Calcareous fossils are the only other
calclte present in these muds. Folk believes that psuedospar is of
neomorphic origin; however, Bathurst (1975) believes most of Folk's
loaf-shaped crystals may be formed by the breakdown of skeletal
material. Because there is a lack of micrite and ralcrospar which, if
present, might suggest a neomorphic origin, a skeletal origin is favored
for loaf-shaped crystals where clays and other insoluble matrix material
are abundant.
Interbedded Carbonates
Interbedded carbonates are those in which indurated carbonate
laminae overlie and are overlain by noncarbonate lithologies. Two types
of interbedded carbonate sediments were seen: echinoid-foramlniferal
blosparite and moldic microsparite.
Echinoid-foramlniferal Biosparite. Two beds, 5cm and lOcm thick, of
echinoid-foramlnlferal biosparite (Plate 12) occur in seismic unit FPF-6
(core OB-102) in the Frying Pan Area. These biosparltes are well washed
(only 6% mud) and are predominated by benthic foraminifers (31.2%),
planktonic foraminifers (22.2%), and echinolds (8.3%). In thin section,
the foraminifers do not appear to be broken or abraded nor are the
fossils laminated. Biosparltes have sharp contacts with the overlying
133
and underlying sediment.
The lithology of the noncarbonate portion of FPF-6 in the Frying
Pan Area is a fossiliferous (29.5%), muddy (31.6%), quartz sand.
Predominant fossils are benthic foraminifers (8.7%), planktonic
foraminifers (6.1%), and echinoids (7.7%). FPF-6 contains a
foraminiferal fauna indicative of well oxygenated, open marine, mid to
outer shelf conditions; planktonic to benthic foraminiferal ratios are
about 1:1 (Waters, 1983). The seismic pattern of FPF-6 in the Frying
Pan Area is a series of large-scale channels (Fig. 6) which are
interpreted to be the product Gulf Stream activities.
Based on the state of preservation of foraminifers in the
biosparites, the minor amount of fine grained sediment, the lack of
bedding of the fossils, the similar species composition of faunas in the
biosparites to those in overlying and underlying sediment, and the
large-scale channeled seismic pattern of FPF-6 (Fig. 6), the biosparites
probably formed as a lag deposit via winnowing of the fines by
moderately low energy, current activity such as meander eddies of the
Gulf Stream. I believe the fines were winnowed by currents rather than
by wave agitation and transportation because the fossils are not abraded
or bedded.
Moldic microsparltes. Moldic microsparites were found in seismic
units FPF-1 and BBF-1 (cores OB-134, 53, and 94). Table 18 summarizes
the composition of the moldic microsparites. They are well cemented by
microsparite (65.9%) and contain few body fossils (2.9%). About 5%
moldic porosity is present due to dissolution of bivalve fragments.
Sample Moll Barn Ech For Spar Micr Phos Oth Qtz
53-5.90 0.0 0.0 0.0 0.0 6.7 81.3 2.7 0.6 8.7
94-1.00 0.0 3.3 0.0 0.0 8.3 72.0 3.7 0.3 12.3
94-1.50 0.0 0.0 0.0 0.0 11.1 63.0 5.9 0.0 20.0
134-0.00 0.6 3.6 2.9 1.3 7.1 47.2 0.3 1.0 35.9
Average 0.2 1.7 0.7 0.3 8.3 65.9 3.2 0.5 19.2
Table 18. Composition of moldic microsparites. (Sample =
core-depth (m); Moll = molluscs; Barn =? barnacles;
Ech = echinoids; For = foraminifers ; Spar = calcite
cernent; Micr = microspar; Phos = phosphate;
Oth - others; Qtz =* siliciclastic sand.
135
Quartz Is a common component, averaging 19.2%.
Moldic microsparite within seismic unit FPF-2 crops out on the sea
floor along the 22ra profile (core OB-134). The relationship of the
microsparite with underlying sediments is unclear because the rock was
too hard to vibracore (only 0.5 m was recovered). However, the 22m
seismic profile suggests it may be the carbonate cap rock of seismic
unit FPF-1.
In seismic unit BBF-1 (cores OB-53 and OB-94), three laminae of
microsparite are Interbedded with quartz-rich (49.9%), phosphorite sand.
The laminae are l-3cm thick and in sharp contact with overlying and
underlying sediments. Thin section analyses indicate that the laminae
are indurated by microspar. Surrouding unindurated phosphorite sand
also contains carbonate mud which has neomorphosed to microspar but is
not indurated because microspar is a minor component and is mixed with
abundant (25.8%) clays. These thin carbonate laminae resemble the cap
rock of "unit C" of the Pungo River Formation in the Aurora Area (Riggs
and others, 1982b). They may indicate the beginning of an increase of
carbonate upsectlon but better core control will be neccessary to
document this interpretation.
136
SUMMARY
1. Four patterns of carbonate sedimentation occur in the Fungo River
Formation in Onslow Bay: 1) cyclic carbonate sediments overlying
noncarbonate lithologies which were deposited as a couplet during the
same sea-level cycle (carbonate caps); 2) barnacle-rich, relatively pure
carbonate sediments of seismic sequence AF which were deposited
continuously during each fourth-order sea-level cycle of the Langhian;
3) thin carbonate laminae Interbedded with noncarbonate lithologies; and
4) disseminated sparse fossils and carbonate mud in noncarbonate
lithologies. The total carbonate content of the Fungo River Formation
in Onslow Bay is summarized in Figure 40. The distribution of carbonate
mud and calcareous faunal assemblages in Fungo River sediments are shown
in Figures 41 and 42, respectively.
2. Two types of carbonate cap rocks are present in the Fungo River
Formation in Onslow Bay; a) those that fit Riggs' (1984) model of
Neogene sedimentation, and b) barnacle-rich carbonates which could
represent a variation of the idealized lithic cycle in Riggs' model.
Two varieties of carbonate cap rocks which fit Riggs' (1984) model
occur in Fungo River sediments in Onslow Bay. Seismic unit FFF-1 in the
Frying Fan Area has a biomicrosparite cap that overlies and grades into
phosphorites. It contains a diverse fauna and flora of barnacles,
bryozoans, bivalves, echlnoids, benthic and planktonic foraminlfers,
ostracods, decapods, and coralline and dasycladacean algae. This
assemblage Indicates open shelf conditions and warm temperate to
137
Total Carbonata Contant
2S-50%
,0-25» >50»
Figure 40 . Map of the Fungo River Formation showing the distribution
of carbonate sediments.
138
Carbonata Mud
o-s%
SSfxSÎ
Figure 41. Map of the Fungo River Formation showing the distribution
of carbonate mud.
139
Calcaraoa* Fosall Aaaamblagas
Fottilt Barnacla*Cchinofd*Foram*Mollusc
Barflacl«t roram«£chinoid
MOllutCS oraminif ara
Figure 42 Map of the Pungo River Formation showing the distribution
of calcareous fossil assemblages.
140
subtropical waters. The second "carbonate" cap rock is calcite cemented
sandstone of seismic unit BBF-2. Total carbonate content and affects of
diagenesis decrease down section.
Barnacle-rich carbonate sediments consisting mostly of barnacles,
with minor echinoids and molluscs, probably were formed on the inner
shelf. These carbonate sediments were probably deposited during
fourth-order sea-level regressions during which the barnacles were
disarticulated and scattered over the top of previously deposited
siliciclastic sediment.
3. The AF seismic sequence is predominated by carbonate sediments in
the northern part of Onslow Bay; siliciclastics decrease upsection and
increase toward central Onslow Bay. Sediments of unit AF-1 in northern
Onslow Bay contain a diverse assemblage of calcareous and siliceous
fossils including molluscs, barnacles, echinoids, bryozoans, ostracods,
benthic and planktonic foraminlfers, diatoms, radiolarlans, and
siliceous sponge spicules. This assemblage indicates open shelf
conditions, probably mid to outer shelf. AF-2 and AF-3 both contain
largely reworked fossil assemblages. AF-4, predominated by barnacles
and bryozoans, is interpreted as outer shelf to upper slope deposition.
4. Two types of interbedded carbonate lithologies occur in Fungo River
sediments in Onslow Bay: 1) echinoid-foraminiferal biosparite and 2)
moldic microsparite. Echinoid-foraminiferal biosparites of seismic unit
FPF-6 are probably formed via winnowing of the fines by Gulf Stream eddy
currents. Moldic microsparite crops out on the sea floor along the 22m
141
profile and Is Interpreted as the carbonate cap rock on FPF-1 in
northern Onslow Bay. Seismic unit BBF-1 contains three moldic
microsparite laminae which are interbedded with quartz-rich phosphorite
sand. These laminae are similar to the carbonates in "unit C" of the
Pungo River Formation in the Aurora Area and they may indicate the
beginning of increased carbonate deposition.
5. The most common fossils in noncarbonate lithologies of Pungo River
sediments in Onslow Bay are echinoids, bivalves, and benthic
foramlnifers. Barnacles, bryozoans, and ostracods constitute a small
percentage of these sediments.
6. The source of carbonate mud in the Pungo River Formation is largely
from bio-mechanical degradation of larger carbonate grains, primarily
shell material.
7. Vertical diagenetic profiles are exhibited by some, but not all, of
the cores studied. This may be due to the sampling interval used, the
actual distribution of different diagenetic components, the effects of
multiple diagenetic processes, or a combination of these factors. More
detailed work at -a close sample interval needs to be done with cores
that have a thick Miocene section to determine the details and extent of
diagenetic alteration.
Where carbonate sediments are abundant, affects of fresh water
calcite cementation decrease down section. Syntaxlal cement on
echinoids seems to be a good indicator of the degree of diagenesis
142
undergone by sediments because It appears to be precipitated faster than
rim cements on other fossils.
The occurrence of early diagenetlc dolomite in the Pungo River
Formation appears to be sporadic. This may be attributable to the
presence or absence of sulfate reducing bacteria within the sediment.
Silica authlgenesis appears to be related to concentration of
siliceous fossils and permeability barriers within the sediment which
would explain the preservation of diatoms in parts of the sediment
column and their dissolution in other parts.
143
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Appendix A.
Reflected light microscopy data
153
Appendix A. Reflected light microscopy data.
This data Is arranged first by seismic unit, then by seismic
profile or area (refer to Figure 8 for the location of the seismic
profiles). Each series of cores in the same seismic unit are then
arranged by location from east to west. Area FP is the Frying Pan
Area; cores in this area are listed numerically.
The following data is presented in volume % of the total sediment.
The method by which this was determined is described in detail in the
Methods of Investigation section. The headings are abbreviated as
follows :
Sample = Core-Top depth of sample (m)
Moll = Molluscs
Barn = Barnacles
Bry = Bryozoans
Ech = Echinoids
Ost = Ostracods
Bf = Benthic foraminifers
Pf a Planktonic foraminifers
Garb = Unidentifiable carbonate grains
Spar = Calcite cement
Dolo = Dolomite
Cher = Chert
Diat a Diatoms
Rad = Radiolarians
Splc = Spicules
Skel = Skeletal phosphate grains
Phos = Pelletai and intraclastic phosphate grains
Glau = Glauconite
Opaq = Opaques
0th = Other minerals (zeolites and gypsum)
Qtz = Slliclclastic sand
Matr =s Matrix
Staple Area Holl Barn •ry Ech Oat Bf Pf Garb Spar Dolo Cher 01.c Rad Spic Sk.l Phoe Clau Op.S 0th Ota Natr
BBF-6
100-8.60 15. tr tr 0.0 0.6 0.0 tr 0.0 0.6 0,1 0,2 0.0 0,0 0.0 0.0 0.1 cr 0.0 cr 0.4 53.5 44.4
1-4,50 15. 0,3 tr 0.0 l.l 0.0 2.0 0.0 O.A 0.0 1,6 0.0 0,0 0.0 0.0 2.8 8.A 0.1 0.0 0.0 62.1 21.3
1-5,25 15. 0.0 0.0 0.0 O.A 0.0 3,7 0.0 0.4 0,0 2,4 0.0 0,0 0.0 0.0 2.7 6.4 0.2 0.0 0.0 60.2 23.6
1-5,75 15b 0.2 0.0 0.0 cr 0.0 0.6 0.0 O.l 0.0 0,7 0.0 0.0 0.0 0.0 3.0 5.6 0.1 0.0 0.0 63.7 26.1
1-6,50 15. cr tr 0.0 0,1 0.0 0.5 0.0 0,2 0.0 0,2 0,0 0.0 0.0 0.0 4.7 8.5 0.1 0.0 0.0 65.6 20.1
1-8.00 15a 0.0 tr 0.0 tr 0.0 0.6 0.0 tr 0.0 0.7 0.0 0.0 0.0 0.0 3.5 10.5 0.2 0.0 0.0 67.0 17.5
BBP*3
108-2.75 22a 0.4 6.6 0.2 0.4 0.1 1.7 0.0 1.8 cr 0.0 0.0 0.0 0.0 0.0 0.2 cr cr 0.0 0.0 10.9 77.8
108-3.75 22b 0.7 18.7 0.1 1.0 0.0 1.3 0.0 5.0 5.8 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 0.0 0.0 27.6 39.5
108-5.00 22. 0.3 9.3 0.1 0.6 0.0 1.7 0.2 2.2 9.3 0.0 0.0 0.0 0.0 0.0 0.2 cr 0.0 0.0 0.0 21.2 54.9
BBP-2
92-4.00 1-4 0.1 cr 0.0 0.1 0.0 tr 0.0 1.2 0.8 0.0 0.0 0.0 0.0 0.0 Cr Cr 0.0 0.0 0.0 83.9 13.9
92-5.50 1-4 0.4 0.0 0.0 0.1 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cr cr 0.0 cr 0.0 93.4 6.0
BBF-1
91-3.50 15a cr 0.0 0.0 tr 0.0 0.9 0.0 tr 0.0 0.8 0.0 0.0 0.0 0.0 2.9 7.4 1.6 0.0 0.0 66.9 19.4
91-5.50 15a 0.0 0.0 0.0 tr 0.0 0.9 0.0 tr 0.0 0.6 0.0 0.0 0.0 0.0 1.3 2.6 1.1 0.0 0.0 71.6 21.9
2-3.50 15a 0.0 0.0 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.5 2.1 1.2 0.0 0.0 67.6 27.0
2-6.50 15b 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.5 0.0 0.0 0.0 0.0 1.5 4.4 0.0 0.0 0.0 59.0 34.5
2B-6.50 15a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 0.0 0.0 0.0 0.0 0.0 3.4 10.1 0.0 0.0 0.0 50.4 35.1
3-1.50 15a 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 4.5 0.0 0.0 0.0 16.8 76.8
3-4.00 15b 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.0 3.5 11.7 0.0 0.0 0.0 45.6 39.2
3-6.50 15. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.5 12.6 0.0 0.0 0.0 46.5 36.3
36-2.00 15. 0.3 0.0 0.0 tr 0.0 cr 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2.3 6.6 0.0 0.0 0.0 60.1 30.5
109-1.50 22. 0.3 0.2 0.0 0.0 0.0 0.4 0.0 tr 0.0 cr 0.0 0.0 0.0 0.0 2.7 4.3 tr 0.0 0.0 65.7 26.3
109-3.00 22a 0.2 0.0 0.0 0.5 0.0 0.6 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.0 2.8 4.0 0.1 0.0 0.0 62.8 28.9
109-4.50 22a 0.2 0.0 0.0 0.0 0.0 tr 0.0 0.2 0.2 tr 0.0 0.0 0.0 0.0 2.8 2.8 0.3 0.0 0.0 60.6 32.8
109-5.75 22a 3.8 15.3 0.0 2.8 0.2 4.9 0.0 0.4 0.0 0.0 0.0 0.0 0.0 0.0 1.6 1.1 0.1 0.0 0.0 26.6 43.2
71-0.50 22a 0.1 cr 0.0 0.1 0.0 1.0 0.0 cr 0.0 0.2 0.0 0.1 0.0 0.0 1.4 1.9 0.1 0.0 0.0 29.4 65.6
6-2.00 22. cr cr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 2.7 0.0 0.0 0.0 50.7 45.9
6-5.00 22. cr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.6 0.1 0.0 0.0 49.0 48.2
39-2.00 22. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 2.1 0.0 0.0 0.0 49.9 47.7
39-5.00 22a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.9 2.9 0.0 0.0 0.0 47.4 48.6
60-1.50 1-4 0.1 2.6 0.0 tr 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.6 0.0 0.0 0.0 66.1 30.1
60-4.00 1-4 0.1 2.0 0.0 Cr 0.0 0.1 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.9 1.4 0.0 0.0 0.0 42.9 52.5
60-6.25 1-4 0.3 1.1 0.0 0.4 0.0 0.2 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 1.1 4.2 0.0 0.0 0.0 49.3 43.4
53-1.50 1-4 0.4 0.7 0.0 0.1 0.0 0.4 0.0 cr 0.0 0.0 0.0 cr 0.0 0.0 1.4 7.6 0.0 0.0 0.0 52.0 37.3
53-3.75 1-4 0.2 0.6 0.0 cr 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.4 22.2 0.3 0.0 tr 45.9 24.0
53-6.00 1-4 1.7 1.7 0.2 0.9 0.0 0.3 0.0 1.4 1.1 0.0 0.0 0.0 0.0 0.0 3.9 14.2 0.2 0.0 0.0 42.9 31.5
52-3.75 1-4 0.1 cr cr 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1 tr 0.0 tr 0.0 7.4 92.2
59-6.50 1-5 cr tr 0.0 0.6 tr 0.6 0.1 6.0 2.9 0.0 0.0 0.0 0.0 0.0 0.2 tr 0.0 0.0 tr 6.1 83.4
59-7.75 1-5 3.8 0.7 cr 0.4 0.1 1.0 0.0 0.2 tr 0.0 0.0 0.0 0.0 0.0 0.6 0.5 0.3 0.0 0.3 72.7 19.2
154
Saaple Area Holl Barn 8ry Ech Oat Bf Pf Carb Spar Dolo Cher Dtat Rad Spic Sk«l Phoa Clau Opaq Ot h Qta Hatr
AF-4
3-8.75 15* 1.9 49.0 0.5 0.7 0.0 0.4 tr 3.7 4.3 cr 0.0 0*0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.1 19.1
36-5.00 15« 0.0 4.3 0.0 tr 0.0 2.1 0.3 1.3 0.0 0.7 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.1 91.1
33-0.50 15. 20.6 42.5 0.7 0.0 0.0 tr tr 8.8 0.3 Cr 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.1 26.9
33-2.50 15« 10.3 65.6 3.0 tr tr tr tr 1.5 1.1 cr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.1 18.1
13-4.50 15a 9.3 27.6 12.4 1.2 tr 0.5 tr 9.8 0.0 0.1 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.1 0.0 0.8 38.2
33-6.50 15b 7.0 18.6 8.5 2.1 0.4 1.5 0.5 1.8 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.3 0.0 0.0 1.1 2.9 55.3
33-8.75 15b 2.3 46.4 2.6 3.8 tr 0.9 0.2 6.1 1.9 0.0 0.0 0.0 0.0 0.0 tr 0.2 0.0 0.1 0.0 1.7 31.7
111-0.50 15a 15.3 13.4 5.6 0.1 0.0 tr tr 6.0 38.2 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr tr 1.4 19.8
111-2.50 15a 15.1 28.0 3.2 0.5 tr 0.2 0.0 3.1 0.0 1.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.6 47.7
111-4.25 15a 3.0 42.8 7.3 0.4 0.0 0.3 0.0 10.5 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 4.1 27.4
111-5.50 15a 9.5 17.5 7.4 0.6 0.2 1.4 0.2 7.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.7 55.5
111-6.25 15a 9.8 39.4 5.6 0.5 tr 0.5 cr 4.4 10.9 0.0 0.0 0.0 0.0 0.0 tr tr 0.0 tr 0.0 1.1 27.4
111-7.50 15a 9.8 12.4 5.8 0.7 0.0 1.0 0.3 8.5 0.0 0.0 0.0 0.0 0.0 tr tr 0.1 0.0 0.0 0.0 1.4 60.1
111-8.00 15. 16.6 44.9 2.1 0.3 0.0 0.1 tr 5.6 2.8 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.1 0.0 2.0 25.6
AF-3
34-2.00 15. 0.4 21.9 0.7 5.6 0.0 0.2 0.1 3.2 7.9 0.0 0.0 0.0 0.0 0.0 tr 0.7 0.0 0.2 0.0 29.9 29.2
35-1.25 15a 2.5 26.9 0.5 6.9 0.4 2.1 0.7 9.0 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.3 tr 0.1 0.0 14.3 36.5
131-3.75 1-5 10.9 3.0 1.3 3.4 0.0 0.8 0.1 8.7 7.3 0.0 0.0 0.0 0.0 0.0 tr 0.2 0.0 0.0 0.0 30.1 33.9
131-4.75 1-5 8.4 7.8 1.6 4.3 0.0 1.1 0.2 9.7 3.2 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 12.6 10.8
131-5.75 1-5 10.1 6.3 1.5 2.4 0.0 0.7 0.1 11.1 2.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 36.7 28.8
AF-2
39-8.40 22a 4.0 41.9 0.4 2.2 0.0 1.8 0.5 4.2 1.2 0.0 0.0 0.0 0.0 0.0 0.5 0.6 0.2 0.0 0.0 29.1 13.3
38-0.50 22a 1.4 21.3 0.0 2.1 0.0 12.5 4.6 13.3 22.4 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.3 0.0 0.0 3.3 18.7
58-2.25 1-5 cr 0.1 0.0 0.2 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.2 0.0 0.0 0.0 94.5 4.8
58-4.25 1-5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.0 2.7 97.3
AF-1
34-4.00 15. 0.1 4.2 0.3 1.7 0.0 0.5 0.2 3.4 cr cr 0.0 1.4 cr tr 0.0 tr 0.0 tr 0.0 9.3 78.9
34-6.00 15a 0.1 1.8 0.1 0.5 0.1 0.2 0.1 0.8 0.0 0.0 0.0 2.5 tr tr tr 0.0 0.0 0.0 tr 3.8 90.0
34-8.00 15b 0.7 18.9 0.9 6.3 0.5 0.9 0.2 6.6 0.0 tr 0.0 0.1 0.0 0.0 0.0 0.2 tr 0.0 0.0 26.3 38.5
35-2.75 15b 0.2 3.1 0.3 8.1 0.4 3.2 0.5 10.8 0.0 0.1 0.0 0.0 0.0 0.0 0.5 0.4 0.0 0.0 0.0 12.260.3
35-5.25 15a 6.0 3.4 0.6 3.2 0.4 2.6 0.4 7.6 cr 0.1 tr 0.0 0.0 0.0 0.2 0.4 0.0 0.0 0.0 11.7 61.5
35-7.75 15a 7.1 1.1 0.5 1.9 3.4 11.0 1.0 8.0 0.0 0.2 0.0 0.0 0.0 0.0 0.2 0.4 0.0 0.0 0.0 9.7 55.5
38-3.50 22a cr 0.0 0.0 tr 0.0 0.0 0.0 cr cr 0.5 0.0 0.0 0.0 0.0 0.4 0.6 0.0 0.0 0.0 68.7 29.8
38-6.50 22. 0.0 0.0 0.0 cr 0.0 0.0 0.0 tr 7.5 tr 0.8 0.0 0.0 0.0 0.0 0.2 0.0 tr 0.0 28.662.8
38-8.75 22b tr cr 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.6 tr 0.0 0.0 94.6 2.8
40-8.00 22a cr Cr 0.0 0.0 0.0 tr 0.0 tr 0.0 tr 0.0 0.0 0.0 0.0 0.3 0.1 0.0 tr 0.2 26.7 72.6
41-2.50 1-8 3.4 0.3 0.2 0.4 0.0 tr cr 4.2 tr tr 0.0 0.0 0.0 tr 0.4 0.1 0.0 tr tr 78.6 12.2
41-4.75 1-8 tr cr cr tr 0.0 tr 0.0 4.1 1.9 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.0 tr 0.0 83.4 10.4
41-7.00 1-8 0.2 0.1 0.0 tr 0.0 0.0 0.0 0.4 2.3 0.0 0.0 0.0 0.0 0.0 tr 1.1 0.0 tr 0.0 86.9 8.8
44-2.00 1-8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.0 0.0 0.0 0.0 tr tr 0.1 0.0 0.0 tr 2.5 97.2
44-5.00 1-8 0.0 0.0 0.0 tr 0.0 tr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr 0.2 0.2 0.0 0.0 0.0 56.5 43.1
155
Staple Ar«â Holl B«rn Bry Ech 0»t Bf Pf Carb Spar Dolo Cher Diet Red Sptc Skel Phoe Gleu Op«<) 0th Qtt Hetr
AF-l
51-2.00 1-4 tr 0.0 0.0 0.3 0.0 tr 0.0 0.0 2.2 0.0 0.0 0.0 0.0 0.0 0.5 1.1 0.0 0.0 0.0 73.8 20.1
51-5.00 1-6 0.0 tr 0.0 0.1 0.0 0.0 0.0 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.7 0.0 0.0 0.0 69.9 26.8
5t>6.00 1-4 tr 0.1 0.0 0.6 0.0 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.5 0.6 0.0 0.0 tr 60.4 37.6
58-6.25 1-5 0.1 tr 0.0 0.0 0.0 tr 0.0 tr 0.1 0.0 0.0 0.0 0.0 0.0 tr 0.4 0.0 0.0 0.0 96.8 4.6
58-8.25 1-5 tr tr 0.0 tr 0.0 0.0 0.0 0.1 1.5 0.0 0.0 0.0 0.0 0.0 0.1 0.6 0.0 0.0 0.0 88.5 9.2
FPf-6
45-1.00 i-e 0.5 27.5 0.5 5.6 0.0 1.7 0.1 9.8 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0,5 0.0 0.0 0.0 8.7 44.9
45-1.00 1-8 0.2 1.9 0.8 11.6 0.0 2.9 0.6 2.6 1.1 0.0 0.0 0.0 0.0 0.0 0.4 0.9 tr 0.0 0.0 50.1 22.9
45-4.00 1-8 4.4 5.7 0.8 2.9 0.0 0.4 0.1 2.8 0.7 0.0 0.0 0.0 0.0 0.0 0.9 0.6 0.0 0.0 0.0 52.9 27.5
65-5.50 1-8 3.1 8.2 tr 1.6 0.0 0.7 0.4 4.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 tr tr 0.0 68.9 12.6
67-1.50 PP tr 0.0 0.0 8.1 tr 8.8 11.7 1.7 0.5 0.0 0.0 0.0 0.0 0.0 1.0 0.8 0.0 0.0 0.0 19.5 21.6
67-6.50 FP 0.0 0.0 0.0 8.1 0.2 7.5 7.1 1.6 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.4 0.0 0.0 0.0 41.6 10.2
86-1.50 FP 0.4 0.4 tr 11.8 0.2 10.4 6.9 22.8 6.9 0.0 0.0 0.0 0.0 0.0 1.1 0.1 0.0 0.0 0.0 16.9 23.9
96-1.50 FP 0.0 tr 0.0 6.0 tr 8.9 1.6 5.6 tr 0.0 0.0 0.0 0.0 0.0 1.1 1.1 0.0 0.0 0.0 41.4 10.6
96-5.50 FP 0.0 tr 0.0 4.0 0.0 8.1 1.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 0.6 0.2 0.0 0.0 0.0 14.8 49.9
rPF-5
46-0.75 1-8 0.6 31.6 0.5 6.9 0.1 2.6 0.3 16.8 0.0 0.2 0.0 0.0 0.0 0.0 0.0 O.l 0.0 0.2 0.0 5.2 36.9
46-2.50 1-8 0.2 0.2 tr 0.0 0.0 tr tr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.6 tr 0.0 0.0 0.0 85.3 13.0
66-5.50 1-8 tr 0.1 0.0 tr 0.0 tr 0.0 tr tr 0.0 0.0 0.0 0.0 0.0 tr 0.1 0.0 tr 0.0 88.0 11.6
50-2.50 1-4 8.1 8.4 1.0 4.5 0.0 0.9 0.6 6.7 4.4 0.0 0.0 0.0 0.0 0.0 0.1 0.7 tr tr 0.0 44.4 19.9
50-3.25 1-6 5.3 3.7 0.0 2.7 0.0 1.5 0.3 6.0 2.0 0.0 0.0 0.0 0.0 0.0 0.5 0.8 0.0 0.0 0.0 65.2 16.1
50-5.75 1-4 0.0 tr 0.0 0.1 0.0 tr 0.0 tr 0.0 0.0 0.0 tr 0.0 0.0 0.1 0.4 0.0 0.0 0.0 1.6 95.8
50-8.25 1-4 0.0 0.0 0.0 tr 0.0 0.0 tr 0.1 0.0 0.0 0.0 0.5 0.0 tr 0.1 0.1 0.0 0.0 0.0 6.6 92.4
FPF-4
37-3.00 15a 0.3 tr 0.0 0.2 tr 0.2 0.0 tr tr 0.0 0.0 0.0 0.0 0.0 0.9 tr 0.0 0.0 0.0 88.1 10.2
37-6.00 15. 12.8 4.8 0.0 0.0 0.0 0.0 0.0 0.9 tr 0.0 0.0 0.0 0.0 0.0 0.2 tr 0.0 0.0 0.0 70.5 10.7
1 o 15. 46.2 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.1 0.0 0.0 38.8 10.1
FPP-1
68-2.00 1-4 0.6 0.5 0.1 1.7 0.1 0.3 0.1 2.6 0.1 0.0 0.0 0.0 0.0 0.0 0.2 l.O tr 0.0 0.0 78.6 16.2
48-5.00 1-4 0.1 1.5 tr 1.5 0.1 2.8 0.4 5.6 tr 0.0 0.0 0.0 0.0 0.0 0.9 1.6 0.0 1.1 0.0 74.0 10.6
68-7.75 1-6 tr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.0 0.0 1.5 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 61.2 27.2
17-3.25 FP 0.0 0.0 0.0 tr 0.0 1.5 tr 0.0 0.0 tr 0.0 tr 0.2 0.1 0.2 0.6 0.0 0.0 0.0 1.4 91.9
17-5.50 FP tr tr 0.0 0.2 0.0 6.4 0.4 0.0 tr 0.0 0.0 0.0 0.2 tr 0.1 0.5 0.0 0.0 0.1 8.2 81.6
62-1.75 FP tr tr tr tr 0.0 0.1 tr tr 0.0 0.0 0.0 tr 0.1 tr tr tr 0.0 0.0 0.0 0.5 99.2
62-5.50 FP tr 0.0 tr 0.0 0.0 0.1 tr tr 0.0 0.0 0.0 0.1 0.1 0.1 tr tr 0.0 0.0 0.0 0.9 98.7
FPF-2
110-1.00 22a 0.4 tr 0.0 0.5 0.0 0.1 0.2 l.l 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 tr 87.8 8.8
110-4.64 22a 1.2 0.1 tr 0.1 tr 0.2 0.9 tr 0.0 0.0 0.0 0.0 0.0 0.0 0.1 tr 0.0 0.0 0.2 60.5 36.6
156
Saaplc Area Holl Barn Bry Ech OaC Bf Pf Carb Spar Dolo Cher Diat Rad sptc Skel Phoa Clau Opaq Oth Ota Nacr
FPr-2
49-1.75 1-4 tr cr 0.0 tr 0.0 cr 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.7 0.0 0.0 0.0 66.3 32.4
49-4.75 1-4 0.0 cr 0.0 0.4 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.4 0.7 0.1 0.0 0.0 40.9 57.4
49-7.75 1-4 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.9 tr 0.0 0.0 0.1 0.0 0.0 0.7 0.6 0.0 tr 0.0 54.2 43.6
47-0.50 1-4 O.l 0.1 tr cr 0.0 0.0 0.0 cr Cr 0.0 0.0 0.1 cr 0.0 0.1 0.1 0.0 0.0 0.0 17.2 82.2
47-2.75 1-4 Cr 0.0 0.0 0.0 0.0 cr 0.0 tr 0.0 0.0 0.0 1.3 0.2 0.0 0.1 0.1 0.0 0.0 cr 19.3 79.0
47-5.00 1-4 0.0 cr 0.0 cr 0.0 cr cr cr 0.0 0.0 0.0 2.4 cr 0.1 tr 0.4 0.1 tr 0.0 20.7 76.1
47-7.25 1-4 tr cr tr tr 0.0 Cr tr cr 0.2 0.0 5.1 0.1 0.1 tr 0.4 0.3 0.0 0.0 0.2 17.8 75.8
15-0.25 PP cr cr tr cr 0.0 0.6 0.0 0.3 0.0 0.1 0.0 0.0 0.1 0.3 0.7 0.4 0.0 0.0 0.0 7.9 89.6
15-1.75 FP tr cr 0.0 0.0 0.0 cr 0.0 cr cr 0.1 0.0 0.0 0.0 0.0 0.6 0.9 0.0 0.0 0.0 8.2 90.0
16-1.50 FP 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.0 cr cr cr 0.0 0.0 0.0 0.0 0.1 99.9
16-5.50 FP 0.0 0.0 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.0 0.0 cr Cr cr Cr 0.0 0.0 0.0 0.0 tr 99.9
27-1.00 FP 0.0 0.0 0.0 0.0 0.0 0.7 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 3.2 0.7 94.7
27-3.00 FP cr 0.0 0.0 tr 0.0 3.1 2.7 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.4 1.2 92.4
27-5.00 FP tr 0.0 tr cr 0.0 5.1 0.5 0.0 1.9 0.0 0.0 0.0 0.0 0.0 1.0 1.3 0.0 0.0 tr 16.8 73.3
27-7.00 FP 0.0 cr tr 0.0 0.0 6.0 0.2 0.0 0.2 0.0 0.0 0.0 0.0 0.0 2.1 3.4 0.2 0.0 0.0 33.2 54.7
63-0.75 FP cr tr 0.0 0.0 0.0 10.6 10.7 0.7 0.4 0.0 0.0 0.0 0.0 0.0 0.3 0.1 0.0 0.0 0.0 1.3 75.9
63-2.00 FP 1.1 0.1 0.2 0.2 0.0 19.1 6.2 2.9 4.3 0.0 0.0 0.0 0.0 0.0 2.8 9.1 0.0 0.0 0.0 3.9 49.9
70-1.50 FP tr 0.0 0.0 0.0 0.0 cr tr cr 0.0 0.2 0.0 0.0 0.0 0.0 0.2 0.3 0.0 0.0 0.4 2.5 96.4
97-0.50 FP 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.2 tr 0.0 0.0 0.0 0.0 0.0 2.1 2.9 0.0 cr 0.0 45.3 49.4
97-2.50 FP cr tr 0.0 0.0 0.0 cr tr 0.0 cr 0.0 0.0 0.0 0.0 0.0 3.2 1.4 0.0 0.0 cr 56.0 39.3
97-4.50 FP 0.0 0.0 0.0 0.0 0.0 tr Cr 0.5 0.0 0.3 0.0 0.0 0.0 0.0 0.5 0.8 0.0 0.0 tr 31.7 66.2
97-6.50 FP 0.0 0.0 0.0 0.0 0.0 tr 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 1.8 0.0 0.0 0.0 31.4 66.3
FPF-1
47-8.50 1-4 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 1.0 1.3 0.0 0.0 0.0 32.8 64.7
113-0.50 1-4 cr tr tr 0.0 0.0 0.0 0.0 cr 0.0 0.0 0.0 0.0 0.0 0.0 1.8 6.2 0.0 0.0 0.0 48.0 43.9
113-1.50 1-4 tr tr 0.0 0.0 0.0 0.0 0.0 0.0 cr 0.0 0.0 0.0 0.0 0.0 1.8 1.7 0.0 0.0 0.0 61.7 34.7
14-1.00 FP tr 0.0 tr 0.8 tr 23.2 5.8 0.0 Cr 0.0 cr 0.0 0.0 0.0 1.7 3.8 0.0 0.0 0.0 18.7 46.1
14-2.75 FP 0.0 0.0 0.0 0.8 0.0 10.8 4.4 0.0 tr 0.0 0.0 0.0 0.0 0.0 4.8 25.5 0.0 0.0 0.0 20.5 33.3
20-1.50 FP 0.3 0.6 0.2 0.3 0.0 18.3 7.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.3 2.1 0.0 0.0 0.0 10.4 58.5
20-3.75 FP 0.0 tr 0.0 0.1 0.0 13.1 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.8 16.1 0.0 0.0 0.0 17.2 49.6
20-6.00 FP tr 0,0 0.0 0.1 0.0 22.6 7.0 2.1 0.1 0.0 0.0 0.0 0.0 0.0 2.2 15.3 0.0 0.0 0.0 17.0 33.7
26-0.50 FP tr cr 0.0 0.3 0.0 19.1 5.2 0.1 o.l 0.0 0.0 0.0 0.0 0.0 3.7 8.6 0.0 0.0 0.0 20.2 42.7
64-3.50 FP cr 5.1 3.3 0.6 0.1 8.9 0.8 3.8 cr 0.0 0.0 0.0 0.0 0.0 3.2 14.0 0.0 0.0 0.0 17,5 42.6
64-5.75 FP 0.0 tr 0.0 0.1 0.0 6.5 1.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.9 36.9 0.0 0.0 0.0 19.2 28.7
114-5.75 FP cr tr 0.0 0.1 0.0 29.7 7.2 2.5 cr 1.0 0.0 0.0 0.0 0.0 2.4 2.6 0.0 tr 0.0 7.3 47.0
114-7.50 FP 0.1 cr 0.0 0.1 cr 15.2 0.9 0.5 0.1 0.1 0.0 0.0 0.0 0.0 4.1 14.4 0.0 0.0 0.0 23.3 41.1
115-5.00 FP 2.7 25.4 4.7 2.8 0.0 7.8 1.4 4.3 5.3 0.0 0.0 0.0 0.0 0.0 3.6 15.0 0.0 0.0 0.0 7.8 19.1
115-5.50 FP 0.2 2.3 0.4 0.2 0.0 14.5 4.5 2.8 tr 0.0 0.0 0.0 0.0 0.0 4.0 28.4 0.0 0.0 0.0 15.2 27.5
115-7.00 FP 1.0 0.0 0.0 tr 0.0 3.2 0.6 0.1 0.0 0.0 0.0 0.0 0.0 0.0 4.3 29.3 0.0 0.0 0.0 37.5 24.0
157
Appendix B.
Insoluble residue and x-ray diffraction data
159
Appendix B. Insoluble residue and x-ray diffraction data.
This data is arranged first by seismic unit, then by seismic
profile or area (refer to Figure 8 for the location of the seismic
profiles). Each series of cores in the same seismic unit are then
arranged by location from east to west. Area FP is the Frying Pan
Area; cores in this area are listed numerically.
Total weight % of matrix in the sediment was determined by wet
seiving. Insoluble residue analysis resulted in the determination of
weight % of Insolubles and carbonate in the matrix and the weight % of
mud-sized Insolubles and carbonate in the total sediment. Presence (P)
and absence (A) of calcite and dolomite were determined by x-ray
diffractometry of a split of the mud fraction. It is Important to
remember, however, that when only a few percent of a mineral are
present in the sample being x-rayed that peaks for that mineral may be
very weak or not show up at all. These methods are described in detail
in the Methods of Investigation section.
160
CO
9) 0) *T3 CO T3
M-l iJ 0) 4J Qj CO
o CO N o N 4J
3 c o
X. o CO CO u
4J Q) o X 1 C 1
(X a 4J X CO u •o c
<U X iJ c CO D D •H
a bO •H o a CO a
0) •H C X X 0) 0)
CUfH 01 «H AJ X 4J u AJ 0^
o o« » c u U X c CO c 0) iJ
H a X <u ?U 4J u 4J U 3 0) 4J e a> 4J
1 <0 1—1 s X eg X CO X a X o a a
01 cn flS <0 U bo a bO a bo O t-» bO X f-i o o
V JJ 4J •H •H •H CO Tt u
O <4-( u orno; V c 0) c 0) c 0) 0) CO Oi CO o
o o < H e to 5 -H 3 3 •H CO 3 o CO u o
BBF-6
100-8.60 15m 44.4 20.7 79.3 9.2 35.2 P P
1-4.50 15m 21.3 27.0 73.0 5.8 15.6 P P
1-5.75 15m 26.1 57.6 42.4 15.0 11.1 P P
1-6.50 15m 20.1 ' 55.1 44.9 11.1 9.0 P P
1-8.00 15m 17.5 79.1 20.9 13.8 3.7 P P
BBF-3
108-2.75 22m 77.8 70.6 29.4 54.9 22.9 P P
108-3.75 22m 39.5 40.7 59.3 16.1 23.4 P P
108-5.00 22m 54.9 40.3 59.7 22.2 32.8 P P
BBF-2
92-4.00 1-4 13.9 16.1 83.9 2.2 11.7 P A
92-5.50 1-4 6.0 76.7 23.3 4.6 1.4 P A
BBF-1
91-3.50 15m 19.4 55.5 44.5 10.7 8.6 P P
91-5.50 15m 21.9 70.8 29.2 15.5 6.4 P P
2-3.50 15m 27.0 81.8 18.2 22.1 4.9 P A
2-6.50 15m 34.5 - - - - P P
2B-6.50 15m 35.1 90.6 9.4 31.8 3.3 A A
3-6.50 15m 36.3 94.8 5.2 34.4 1.9 A A
36-2.00 15m 30.5 95.1 4.9 29.0 1.5 A A
109-1.50 22m 26.3 79.6 20.4 21.0 5.3 A P
109-3.00 22m 28.9 86.0 14.0 24.9 4.0 A A
109-4.50 22m 32.8 75.7 24.3 24.9 8.0 A A
109-5.75 22m 43.2 32.1 67.9 13.9 29.3 P P
71-0.50 22m 65.6 63.2 36.8 41.4 24.1 P P
6-2.00 22m 45.9 92.1 7.9 42.3 3.6 A A
6-5.00 22m 48.2 87.2 12.8 42.0 6.2 A A
39-2.00 22m 47.7 91.1 8.9 43.4 4.2 A A
39-5.00 22m 48.6 93.1 6.9 45.2 3.4 A A
60-1.50 1-4 30.1 84.8 15.2 25.5 4.6 A A
53-3.75 1-4 24.0 65.7 34.3 15.8 8.2 A A
53-6.00 1-4 31.5 61.2 38.8 19.3 12.2 P A
52-3.75 1-4 92.2 49.8 50.2 45.9 46.3 A P
59-6.50 1-5 83.4 73.6 26.4 61.4 22.0 P P
59-7.75 1-5 19.2 63.2 36.8 12.2 7.1 P P
161
CO 1^
a> V T3 CÜ •o
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o (0 (4 o N 4J
a c •H 4^ •<i4 o
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4J 0) o 1 c 1
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AF-4
3-8.75 15m 39.1 22.5 77.5 8.8 30.3 P P
36-5.00 15m 91.1 16.2 83.8 14.7 76.4 P P
33-0.50 15m 26.9 7.7 92.3 2.1 24.8 P P
33-2.50 15m 18.3 5.0 95.0 0.9 17.3 P P
33-4.50 15m 38.1 10.8 89.2 4.1 34.0 P P
33-6.50 15m 55.3 36.5 63.5 20.2 35.1 P P
33-8.75 15m 33.7 17.9 82.1 6.0 27.7 P A
111-0.50 15m 19.8 9.5 90.5 1.9 17.9 P P
111-2.50 15m 47.7 9.6 90.4 4.6 43.1 P P
111-4.25 15m 27.4 8.9 91.1 2.4 25.0 P A
111-5.50 15m 55.5 32.8 67.2 18.2 37.3 P A
111-6.25 15m 27.4 16.6 83.4 4.5 22.9 P A
111-7.50 15m 60.1 37.7 62.3 22.6 37.4 P A
111-8.00 15m 25.6 49.4 50.6 12.6 13.0 P A
AF-3
35-1.25 15m 36.5 22.9 77.1 8.4 28.1 P P
131-3.75 1-5 33.9 22.9 77.1 7.8 26.1 P P
131-4.75 1-5 30.8 29.1 70.9 9.0 21.9 P A
131-5.75 1-5 28.8 30.3 69.7 8.7 20.0 P A
AF-2
39-8.40 22m 13.3 55.0 45.0 7.3 6.0 P P
38-0.50 22m 18.7 42.0 58.0 7.8 10.8 P P
58-2.25 1-5 4.8 61.5 38.5 3.0 1.8 P A
58-4.25 1-5 97.3 81.0 19.0 78.8 18.4 A P
AF-1
34-6.00 15m 90.0 76.9 23.1 69.2 20.8 P P
35-2.75 15m 60.3 37.1 62.9 22.4 37.9 P P
35-5.25 15m 61.5 40.2 59.8 24.7 36.8 P P
35-7.75 15m 55.5 38.6 61.4 21.4 34.1 P P
38-3.50 22m 29.8 23.6 76.4 7.0 22.8 A P
38-6.50 22m 62.8 55.8 44.2 35.0 27.7 A P
38-8.75 22m 2.8 20.2 79.8 0.6 2.2 A P
40-8.00 22m 72.6 30.0 70.0 21.8 50.8 A P
41-2.50 1-8 12.2 44.8 55.2 5.5 6.7 P P
162
CO pH
a; at <d pH
ij at 4H at Cd
O cd N o N 4J
3 c •H iJ tH
j: oo 0)4J 00 iJ^ 0) o
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0) *o cw JC 4J c
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V c X
QU^ X at at0) •H u •w a^e •H a^« pH u 4J
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a; CO CO a j: o •H(0 s Bcd u 1-»
u bO B bO B bO o •H bO Xi •Hd) a4J O4J •n •H •H
O CO
•H pH
<4-1 pHu too 09 0) 0) c
CJ 0) c at c ato < at <d atH CdB o00 » •H 3 CO 3 o CO o o
AF-1
41-4.75 1-8 10.4 30.2 69.8 3.1 7.3 P A
41-7.00 1-8 8.8 30.1 69.9 2.7 6.1 P A
44-2.00 1-8 97.2 67.1 32.9 65.3 31.9 A P
44-5.00 1-8 43.1 58.0 42.0 25.0 18.1 A P
51-2.00 1-4 20.1 72.3 27.7 14.6 5.6 A A
51-5.00 1-4 37.4 - - - - A P
58-6.25 1-5 4.6 68.1 31.9 3.1 1.5 A P
58-8.25 1-5 9.2 78.5 21.5 7.2 2.0 A P
FPF-6
45-1.00 1-8 44.9 15.5 84.5 7.0 37.9 P P
45-3.00 1-8 22.9 26.2 73.8 6.0 16.9 P P
45-4.00 1-8 27.5 35.7 64.3 9.8 17.7 P A
67-3.50 FP 23.6 50.6 49.4 11.9 11.7 P A
96-1.50 FP 23.9 31.5 68.5 7.5 16.4 P A
96-3.50 FP 30.4 61.0 39.0 18.6 11.9 P P
96-5.50 FP 41.1 75.7 24.3 37.8 12.1 P P
FPF-5
46-2.50 1-8 13.0 83.2 16.8 10.8 2.2 A A
50-3.25 FP 14.1 46.4 53.6 6.5 7.6 P A
50-5.75 FP 95.8 81.3 18.7 77.8 17.9 A P
50-8.25 FP 92.4 80.5 19.5 74.4 18.0 P P
FPF-4
37-3.00 15m 10.2 79.8 20.2 8.1 2.1 P A
37-6.00 15m 10.7 66.2 33.8 7.1 3.6 P A
37-7.50 15m 10.3 36.0 64.0 3.7 6.6 A A
FPF-3
48-2.00 1-4 14.2 51.7 48.3 7.3 6.9 P P
48-7.75 1-4 27.2 85.2 14.8 23.2 4.0 A P
17-3.25 FP 93.9 87.8 12.2 82.4 11.5 P P
17-5.50 FP 83.6 40.9 59.1 34.2 49.4 P P
62-3.75 FP 99.2 96.9 3.2 96.1 3.1 A P
62-5.50 FP 98.7 94.8 5.2 93.6 5.1 A P
163
CO
0) Q) •O CO
AJ Q) AJ o;
O CO N O N
S c: •H AJ •H
£ i'i O CO CO
4J ^ 0> O 1 C 1
O. a U jC CD U •fj •T3
(U JZ 4J c CO 3 3
O 00 •H O a CO B
0) •H c X X V
(Xi-H 0) •H 4J •H ^ «H pH AJ
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1 CO fH a CO JZ <0 sz B
01 en CO CO w bO a bo a bO O •H bO
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O u-i U O (0 0) o; c 0) C 0) c Oj OJ
U O c H a CO » •H ^ •H 3 •rJ CO 3 Itocnarbtoanatel sediment
FPF-2
110-1.00 22m 8.8 88.6 11.4 7.8 1.0 P A
110-4.64 22m 36.4 92.4 7.6 33.6 2.8 A A
49-1.75 1-4 32.4 49.7 50.3 16.1 16.2 A P
49-4.75 1-4 57.4 84.0 16.0 48.2 9.2 A P
49-7.75 1-4 43.6 79.5 20.5 34.7 8.9 A P
47-0.50 1-4 82.2 88.3 11.7 72.6 9.6 A P
47-7.25 1-4 75.8 76.9 23.1 58.3 17.5 A P
15-0.50 FP 89.6 77.0 23.0 68.9 20.6 P P
15-1.75 FP 90.0 90.8 9.2 81.7 8.3 A P
16-1.50 FP 99.9 94.3 5.7 94.1 5.8 A P
16-5.50 FP 99.9 91.8 8.2 91.7 8.2 A P
27-1.00 FP 94.7 94.6 5.4 89.5 5.1 A A
27-3.00 FP 92.4 88.8 11.2 82.0 10.3 P A
27-5.00 FP 73.3 78.6 21.4 57.6 15.7 P A
27-7.00 FP 54.7 70.0 30.0 38.3 16.4 P P
63-0.75 FP 75.9 80.8 19.2 61.3 14.5 P A
70-1.50 FP 96.4 78.4 21.6 75.6 20.8 A P
FPF-1
47-8.50 1-4 64.7 78.3 21.7 50.7 14.0 A P
113-0.50 1-4 43.9 54.8 45.2 24.0 19.9 A P
113-1.50 1-4 34.7 67.0 33.0 23.2 11.5 A P
114-5.75 FP 47.0 82.8 17.2 38.9 8.1 P P
114-7.50 FP 41.1 47.6 52.4 19.6 21.5 P P
115-5.00 FP 19.1 17.7 82.3 3.4 15.7 P A
115-5.50 FP 27.5 48.6 51.4 13.4 14.1 P A
115-7.00 FP 24.0 59.4 40.6 14.3 9.7 P A
Appendix C
Thin section point count data
165
Appendix C. Thin section point count data.
This data is arranged first by seismic unit, then by seismic
profile or area (refer to Figure 8 for the location of the seismic
profiles). Each series of cores in the same seismic unit are then
arranged by location from east to west. Area FP is the Frying Pan
Area; cores in this area are listed numerically. Core OB-123 is located
approximately midway between seismic profile 1-4 and 1-5.
The following data is presented in volume % of the total sediment
and is based on 300 point counts per slide. The headings are
abbreviated as follows:
Sample = Core-Top depth of sample (m)
Moll = Molluscs
Barn = Barnacles
Bry Bryozoans
Ech = Echlnolds
Ost Ostracods
Bf = Benthic foraminifers
Pf = Planktonic foraminifers
Alg = Calcareous algae
Garb = Unidentifiable carbonate grains
Spar = Calclte cement
Micr = Microspar
Matr 3 Matrix
Dolo = Dolomite
Cher = Microcrystalline quartz
Chai = Chalcedony
Phos = Phosphate grains
Glau 3 Glauconite
Opaq = Opaques
Qtz = Siliclclastic sand
Saaple Area Holl Barn Bry Ech Oat Bf Pf Alg Garb Spar Mtcr Natr Dolo Cher Chai Phos Glau Opaq Qtt
BBF-3
108-1.75 22a 0.3 15.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 46.0 0.0 0.0 0.0 0.0 Ü.0 0.3 0.0 32.3
108-2.25 22n 0.0 25.3 1.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 45.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.7
108-5.00 22a 0.0 11.8 0.0 0.4 0.0 0.7 0.0 0.0 0,0 0.0 58.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 29.1
BBF-2
92-3.25 1-4 1.4 2.5 0.0 0.4 0.0 0.0 0.0 0.0 0.0 20.5 20.9 0.0 0.0 0.0 0.0 3.6 0.0 0.0 50.8
92-3.50 1-4 0.0 1,2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 16.4 10.0 0.0 0.0 0.0 0.0 2.8 0.0 0.0 67.7
BBF-1
94-1.00 1-4 0.0 3.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.3 72.0 0.0 0.0 0.0 0.0 3.7 0.3 0.0 12.3
94-1.50 1-4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.1 63.0 0.0 0.0 0.0 0.0 5.9 0.0 0.0 20.0
53-1.50 1-4 1.7 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 73.7 0.0 0.0 0.0 0.0 5.3 0.0 0.0 18.3
53-5.50 1-4 1.0 0.7 0.0 0.0 0.3 0.7 0.0 0.0 0.0 0.7 58.3 0.0 0.0 0.0 0.0 10.4 0.3 0.0 27.7
53-5.90 1-4 0.0 0.0 0.0 0.0 0,0 0.0 0.0 0.0 0.0 6.7 81.3 0.0 0.0 0.0 0.0 2.7 0.3 0.3 8.7
AF-4
3-8.75 15a 3.3 46.3 1.7 0.0 0.0 0.0 0.3 0.0 0.0 0.0 48.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
33-2.50 15a 5.4 76.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 18.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
33-3.25 15a 6.0 70.3 0.0 1.3 0.0 0.7 0.0 0.0 0.0 0.0 16.3 0.0 4.0 0.0 0.0 0.0 0.0 0.0 1.3
33-4.00 15a 9.7 22.0 21.7 0.7 0.0 0.7 0.0 0.0 0.0 0.0 32.6 0.0 11.7 0.0 0.0 0.0 0.0 0.0 1.0
33-5.25 15a 6.3 45.3 3.7 0.3 0.0 0.0 0.0 0.0 0.0 0.0 39.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.7
33-6.40 i5a 12.6 7.9 3.1 0.9 1.3 2.8 0.3 0.0 11.3 0.0 0.0 50.3 4.7 0.0 0.0 0.9 0.3 0.0 3.5
33-8.00 15a 4.0 12.3 7.7 1.3 1.0 3.0 0.0 0.0 10.7 0.0 55.0 0.0 0.3 0.0 0.0 2.0 0.0 0.0 2.7
111-0.25 15a 14.7 23.3 4.7 0.0 0.0 0.3 0.0 0.0 0.0 0.0 53.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 3.0
111-4.10 15a 4.3 20.7 0.7 1.0 0.0 0.0 0.0 0.0 1.0 0.0 68.0 0.0 0.0 0.0 0.0 0.3 0.0 0.0 4.0
in-4.75 15a 4.3 44.3 3.0 0.3 0.0 0.0 0.0 0.0 0.0 0.3 45.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.7
AF-3
34-2.00 15a 2.3 16.0 0.7 1.7 0.0 0.0 0.0 0.0 1.7 2.7 41.3 0.0 0.0 0.0 0.0 0.7 0.0 0.0 24.0
131-3.00 1-5 1.0 3.0 7.0 2.0 0.0 1.0 0.0 0.0 2.7 0.0 76.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 6.3
131-6.3* 1-5 2.6 14.3 4.7 4.7 0.3 1.3 0.0 0.0 0.3 5.3 55.8 0.0 0.0 0.0 0.0 1.0 0.0 0.0 9.7
AF-2
38-0.50 22a 7.3 37.3 0.0 1.0 0.0 22.1 9.3 0.0 2.0 0.0 3.0 0.0 0.3 0.0 0.0 1.3 5.0 0.0 11.3
58-7.40 1-5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 32,7 1.3 0.0 0.0 65.9
AF-1
35-SEM 15a 0.9 0.0 0.0 0.4 0.0 1.3 1.8 0.0 3.5 0,0 0.0 0.0 5.3 58.9 13.7 1.3 0.0 0.0 12.6
35-6.75 15a 3.3 0.0 0.0 1.0 0.0 4.0 0.0 0.0 9.3 0.0 61.7 0.0 6.3 0.0 0.0 0.3 0.0 0.0 14.0
35-7.25 15a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.7 0.0 0.0 0.0 4.7 68.7 2.7 0.0 0.0 0.0 11.3
35-8.00 15a 2.0 0.0 0.0 1.3 0.0 0.7 0.7 0.0 4.3 0.0 0.0 0.0 7.0 66.0 7.7 0.0 0.0 0.3 10.0
38-7.25 22a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 99.3 0.7 0.0 0.0 0.0 0.0
44-5.90 22a 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 99.0 0.7 0.0 0.0 0.0 0.3
166
Sample Area Holl Barn Bry Ech Oat Bf Pf Alg Carb Spar Hier Hatr Dolo Cher Chai Phoa Glau Opaq Qtz
FPF-6
102-7.00 FP 3.0 0.0 0.0 5.3 0.0 3A.7 29.7 0.0 0.0 11.7 0.0 4.0 0.0 0.0 0.0 0.7 0.0 0.0 10.9
102-7.75 FP 0.3 3.0 0.0 11.3 0.3 27.6 14.6 0.0 0.0 24.0 1.0 8.0 0.0 0.0 0.0 0.6 0.0 0.3 9.3
FPF-3
17-3.00 FP 0.0 0.0 0.0 0.0 0.0 8.0 0.0 0.0 0.0 0.0 0.0 64.7 17.3 0.0 0.0 1.7 0.0 0.7 7.7
FPF-2
47-0.00 1-4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 55.4 12.9 0.0 0.0 6.9 1.7 0.3 22.7
47-7.25 1-4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 80.9 0.0 0.0 0.0 2.3 0.3 0.0 16.4
123-2.00 — 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.7 63.0 0.0 0.0 0.0 0.0 25.3
123-5.07 — 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 A.5 27.5 0.5 3.0 2.0 0.0 62.5
123-6.74 — 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.2 36.4 0.8 1.2 2.0 0.0 44.4
29B-2.75 FP 0.0 0.0 0.0 1.0 0.0 17.3 6.0 0.0 3.3 0.0 0.0 29.3 0.0 0.0 0.0 6.7 0.0 0.0 36.4
29B-6.75 FP 0.7 0.0 0.0 0.0 0.0 10.3 2.3 0.0 3.0 0.0 0.0 46.0 0.0 0.0 0.0 17.7 0.0 0.0 20.0
FPP-1
134-0.00 22b 0.6 3.6 0.0 2.9 0.0 1.0 0.3 0.0 0.0 7.1 47.2 0.0 0.0 0.0 0.0 0.3 0.0 1.0 35.9
14-3.75 FP 0.0 0.0 0.0 0.0 0.0 6.7 2.0 0.0 0.0 0.0 0.0 38.7 0.3 0.0 0.0 30.3 0.0 0.0 22.0
20-0.50 FP 4.9 18.1 2.0 4.3 0.3 0.8 0.0 0.3 10.6 4.0 43.6 0.0 1.4 0.0 0.0 3.7 0.0 0.3 5.7
24-1.25 FP 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 26.3 0.0 0.0 0.0 68.4 0.0 0.0 4.3
24-1.67 FP 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 27.7 0.0 0.0 0.0 0.0 45.0 0.0 0.3 26.0
64-0.75 FP 9.6 19.4 4.8 4.1 0.3 1.3 0.3 0.0 2.2 1.3 43.6 0.0 0.0 0.0 0.0 2.5 0.0 0.0 10.5
64-1.75 FP 9.6 9.6 13.0 4.6 0.3 1.9 0.0 0.0 1.9 0.3 50.2 0.0 0.0 0.0 0.0 1.5 0.0 0.0 7.1
64-2.75 FP 4.8 4.1 0.0 4.1 0.0 4.1 0.7 0.0 2.8 0.0 68.8 0.0 0.0 0.0 0.3 1.4 0.0 0.7 8.2
64-6.00 FP 0.3 6.0 0.0 2.3 0.0 3.3 0.0 0.0 4.3 4.7 52.1 0.0 0.0 0.0 1.3 0.0 0.0 0.0 25.4
64-6.25 FP 4.7 9.2 2.4 2.9 0.6 1.8 0.3 0.9 4.4 0.0 32.6 0.0 0.0 0.0 0.3 0.3 0.0 0.3 39.1
6A-6.37 FP 0.0 0.0 0.0 0.6 0.0 0.6 0.0 0.0 0.0 1.7 79.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17,9
114-2.10 FP 8.7 10.0 6.0 8.0 0.0 1.3 0.0 0.0 4.0 2.3 56.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.3
llA-7.75 FP 0.3 3.7 0.0 1.3 0.0 0.7 0.0 0.0 1.0 0.7 62.2 0.0 0.0 0.0 0.0 0.6 0.0 0.0 29.4
115-1.50 FP 10.7 13.9 23.7 6.0 0.0 4.0 0.3 0.0 0.9 1.3 36.8 0.0 0.0 0.0 0.0 0.9 0.0 0.0 1.6
115-2.50 FP 11.4 10.8 13.3 2.2 0.3 4.0 0.3 0.0 2.2 1.1 45.4 0.0 0.0 0.0 0.0 2.8 0.0 0.0 6.2
115-3.00 FP 11.5 9.0 8.7 7.4 0.6 1.5 0.0 0.3 4.3 1.5 44.3 0.0 0.0 0.0 0.0 5.9 0.0 0.0 5.3
115-4.25 FP 6.2 23.1 3.8 6.0 0.3 1.3 0.3 0.4 2.2 2.8 34.6 0.0 0.0 0.0 0.0 8.8 0.0 0.0 8.2
115-4.75 FP 4.0 19.0 7.7 6.6 0.0 2.2 0.4 0.0 0.0 1.7 36.4 0.0 0.0 0.0 0.0 8.4 0.0 0.0 13.2
Appendix D.
Textural data
169
Appendix D. Textural data.
This data is arranged numerically and is presented in weight % of
the total sediment. Samples are numbered in the following manner;
Core number-Depth in meters below the sediment surface. Individual %
(Ind. %) and cumulative % (Cum. %) are given for each 0.5 phi sand and
gravel fraction up to -2.0 phi. The mud fraction is all material finer
than 63um.
Grain Size Sample 1-4.50 Sample 1-5.25 Sample 1-5.75 Sample 1-6.50 Sample 1-8.00
mm phi Ind. % Cum • % Ind. % Cum • Á Ind. % Cum • Á Ind. % Cum • % Ind. % Cum. !
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0 0 0.07 0.07 0 0
2.00 -1.0 0.04 0.04 0 0 0 0 0.08 0.15 0.04 0.04
1.41 -0.5 0.08 0.12 0 0 0.05 0.05 0.09 0.24 0.08 0.12
1.00 0.0 0.09 0.21 0.12 0.12 0.18 0.24 0.33 0.58 0.40 0.52
0.71 0.5 0.59 0.80 0.93 1.05 0.86 1.09 1.29 1.87 2.48 3.00
0.50 1.0 3.54 4.34 3.98 5.03 3.82 4.91 5.33 7.20 6.27 9.27
0.35 1.5 8.30 12.64 7.66 12.69 6.96 11.87 9.69 16.89 9.50 18.77
0.25 2.0 12.18 24.82 11.75 24.44 10.52 22.39 13.58 30.47 14.75 33.52
0.177 2.5 25.52 50.34 25.78 50.22 26.63 49.02 28.74 59.21 32.77 66.29
0.125 3.0 23.34 73.68 20.43 70.65 19.58 68.60 18.11 77.32 17.01 83.30
0.088 3.5 3.32 77.00 4.07 74.73 3.79 72.39 2.01 79.33 2.56 85.86
0.0625 4.0 1.68 78.68 2.01 76.74 1.48 73,87 0.60 79.92 1.24 87.10
Mud >4.0 21.32 100 23.27 100 26.13 100 20.08 100 12.90 100
Grain Size Sample 2-3.50 Sample 2-6.50 Sample 2B-6.50 Sample 3-1.50 Sample 3-4.00
mm phi Ind. % Cum. % Ind. % Cum • % Ind. % Cum. % Ind. % Cum. % Ind. % Cum.
4.00 -2.0 0 0 0 0 0.83 0.83 0 0 0 0
2.83 -1.5 0 0 0.24 0.24 0 0.83 0 0 0.16 0.16
2.00 -1.0 0.11 0.11 1.06 1.30 0.03 0.86 0 0 0.30 0.46
1.41 -0.5 0.10 0.21 1.41 2.71 0.02 0.88 0.16 0.16 0.47 0.93
1.00 0.0 0.25 0.26 1.78 4.49 0.14 1.02 0.18 0.34 0.64 1.57
0.71 0.5 0.36 0.82 2.17 6.66 3.02 4.04 0.51 0.85 1.80 3.37
0.50 1.0 0.55 1.36 1.63 8.29 10.84 14.88 1.37 2.22 3.05 6.42
0.35 1.5 0.68 2.04 1.56 9.85 18.75 33.63 2.88 5.10 5.68 12.10
0.25 2.0 0.83 2.87 1.87 11.72 18.45 52.08 5.17 10.27 15.10 27.20
0.177 2.5 2.06 4.93 2.17 13.89 6.10 58.18 3.02 13.30 20.28 47.48
0.125 3.0 10.39 15.32 6.59 20.48 1.06 59.24 1.76 15.06 8.46 55.94
0.088 3.5 40.58 55.90 24.42 44.91 1.29 60.53 6.72 21.78 3.17 59.11
0.0625 4.0 19.04 74.94 22.88 67.79 4.86 65.39 3.41 25.19 10.45 69.56 170
Mud >4.0 25.06 100 32.21 100 34.61 100 74.81 100 30.44 100
Grain Size Sample 3-6.50 Sample 3-8.75 Sample 6-2.00 Sample 6-5.00 Sample 14-1.00
mm phi Ind. % Cum. % Ind. % Cum • % Ind. % Cum • Ind. % Cum • /ti Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 6.15 6.15 0 0 0 0 0 0
2.00 -1.0 1.17 1.17 2.01 8.16 0 0 0 0 0 0
1.41 -0.5 0.63 1.80 5.32 13.48 0.13 0.13 0.03 0.03 0.13 0.13
1.00 0.0 0.79 2.59 8.79 22.26 0.24 0.37 0.06 0.09 0.07 0.20
0.71 0.5 2.60 5.19 11.56 33.83 0.49 0.86 0.13 0.22 0.21 0.41
0.50 1.0 3.89 9.09 10.13 43.95 1.31 2.16 0.49 0.71 0.49 0.90
0.35 1.5 6.18 15.27 6.44 50.40 3.07 5.23 1.61 2.32 1.60 2.49
0.25 2.0 11.58 26.85 3.65 54.04 6.90 12.13 4.19 6.51 4.00 6.50
0.177 2.5 9.77 36.62 2.19 56.23 9.84 21.97 6.28 12.80 7.33 13.82
0.125 3.0 5.52 42.14 1.90 58.13 4.75 26.72 4.56 17.36 11.01 24.83
0.088 3.5 3.67 45.80 1.70 59.83 9.47 36.19 13.38 30.74 17.01 41.84
0.06251 4.0 17.86 63.66 1.03 60.85 17.96 54.14 21.05 51.78 18.26 60.10
Mud >4.0 36.34 100 39.15 100 45.86 100 48.22 100 39.90 100
Grain Size Sample 14-2.75 Sample 15-0.25 Sample 15-1.75 Sample 16-1.50 Sample 16-5.50
mm phi Ind. % Cum • % Ind. % Cum. % Ind. % Cura. % Ind. % Cum • /ti Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0.27 0.27 0 0 0 0 0 0 0 0
2.00 -1.0 0 0.27 0 0 0.12 0.12 0 0 0 0
1.41 -0.5 0.05 0.32 0 0 0.02 0.14 0 0 0 0
1.00 0.0 0.16 0.48 0.09 0.09 0.02 0.16 0 0 0 0
0.71 0.5 0.31 0.79 0.09 0.18 0.05 0.21 0 0 0 0
0.50 1.0 0.73 1.52 0.10 0.28 0.12 0.33 0 0 0 0
0.35 1.5 1.54 3.07 0.12 0.40 0.20 0.53 0 0 0 0
0.25 2.0 6.68 9.75 0.18 0.58 0.21 0.74 0 0 0 0
0.177 2.5 13.96 23.71 0.26 0.84 0.24 0.98 0 0 0 0
0.125 3.0 18.38 42.09 0.32 1.16 0.24 1.22 0 0 0 0
0.088 3.5 14.31 56.40 1.59 2.75 1.02 2.24 0 0 0 0
0.0625 4.0 10.80 67.20 7.69 10.44 7.76 10.00 0.15 0.15 0.12 0.12
Mud >4.0 32.80 100 89.56 100 90.00 100 99.85 100 99.88 100 171
Grain Size Sample 17-3.25 Sample 17-5.50 Sample 20-1.50 Sample 20-3.75 Sample 20-6.00
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • Á
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0 0 0 0 0.18 0.18
2.00 -1.0 0 0 0 0 0.16 0.16 0 0 0 0.18
1.41 -0.5 0 0 0.04 0.04 0.21 0.37 0 0 0.03 0.22
1.00 0.0 0 0 0.04 0.08 0.32 0.69 0.07 0.07 0.08 0.30
0.71 0.5 0.02 0.02 0.05 0.13 0.64 1.33 0.18 0.25 0.17 0.47
0.50 1.0 0.04 0.06 0.17 0.30 1.43 2.76 0.49 0.74 0.43 0.90
0.35 1.5 0.23 0.29 1.33 1.63 4.14 6.90 1.24 1.99 1.55 2.45
0.25 2.0 0.31 0.60 1.56 3.19 4.22 11.12 2.58 4.57 3.58 6.03
0.177 2.5 0.39 1.00 1.15 4.34 6.27 17.39 7.28 11.85 10.04 16.07
0.125 3.0 0.42 1.42 0.94 5.28 7.94 25.33 18.53 30.39 27.45 43.52
0.088 3.5 1.30 2.72 2.39 7.67 5.65 30.98 11.37 41.76 16.40 59.92
0.0625i 4.0 3.34 6.06 8.76 16.43 10.52 41.51 8.66 50.42 6.45 66.37
Mud >4.0 93.94 100 83.57 100 58.49 100 49.58 100 33.63 100
Grain Size Sample 26-0.50 Sample 27-1.00 Sample 27-3.00 Sample 27-5.00 Sample 27-7.00
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • Á
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0 0 0 0 0 0
2.00 -1.0 0 0 0 0 0 0 0.29 0.29 0.54 0.54
1.41 -0.5 0.08 0.08 0.11 0.11 0 0 0.05 0.34 0.18 0.72
1.00 0.0 0.09 0.17 0.08 0.19 0 0 0.14 0.48 0.22 0.94
0.71 0.5 0.35 0.52 0.07 0.26 0.02 0.02 0.19 0.67 0.27 1.21
0.50 1.0 0.73 1.25 0.07 0.33 0.08 0.10 0.45 1.12 0.47 1.68
0.35 1.5 2.26 3.51 0.12 0.45 1.06 1.16 1.32 2.44 1.48 3.16
0.25 2.0 6.01 9.52 0.21 0.66 0.86 2.02 1.14 3.58 1.31 4.47
0.177 2.5 10.18 19.70 0.31 0.97 1.17 3.19 1.02 4.60 1.47 5.93
0.125 3.0 8.68 28.38 0.43 1.39 1.13 4.32 1.53 6.13 3.25 9.18
0.088 3.5 11.28 39.66 1.13 2.52 1.33 5.65 8.94 15.07 20.22 29.40
0.0625 4.0 17.64 57.30 2.81 5.33 1.97 7.62 11.62 26.69 15.87 45.27
Mud >4.0 42.70 100 94.67 100 92.38 100 73.31 100 54.73 100 172
Grain Size Sample 33-0.50 Sample 33-2.50 Sample 33-4.50 Sample 33-6.50 Sample 33-8.75
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 12.41 12.41 6.47 6.47 8.91 8.91 0 0 6.60 6.60
2.83 -1.5 4.94 17.35 2.87 9.34 2.16 11.07 0 0 7.88 14.48
2.00 -1.0 6.71 24.06 6.02 15.36 3.43 14.49 2.62 2.62 10.46 24.94
1.41 -0.5 9.53 33.59 13.45 28.81 6.52 21.01 1.32 3.94 10.11 35.05
1.00 0.0 8.80 42.39 15.85 44.66 5.64 26.65 1.21 5.16 5.07 40.12
0.71 0.5 9.57 51.96 16.01 60.67 6.12 32.76 2.33 7.49 3.54 43.66
0.50 1.0 7.28 59.24 10.95 71.62 5.13 37.89 3.78 11.27 2.85 46.51
0.35 1.5 5.40 64.64 5.19 76.81 6.28 44.17 5.64 16.91 3.61 50.12
0.25 2.0 3.45 68.09 2.34 79.15 7.95 52.12 8.42 25.33 5.28 55.40
0.177 2.5 1.80 69.90 1.12 80.27 4.23 56.36 6.31 31.64 3.95 59.35
0.125 3.0 1.48 71.38 0.75 81.02 2.37 58.73 5.02 36.66 2.86 62.21
0.088 3.5 0.99 72.36 0.46 81.48 1.64 60.37 4.81 41.47 2.15 64.36
0.0625 4.0 0.75 73.11 0.25 81.73 1.54 61.91 3.27 44.74 1.91 66.27
Mud >4.0 26.89 100 18.27 100 38.09 100 55.26 100 33.73 100
Grain Size Sample 34-2.00 Sample 34-4.00 Sample 34-6.00 Sample ‘34-8.00 Sample 35-1.25
mm phi Ind. % Gum • Át Ind. % Cum. % Ind. % Cum • % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0.49 0.49
2.83 -1.5 0.55 0.55 0 0 0 0 0.44 0.44 0.64 1.13
2.00 -1.0 1.23 1.78 0 0 0 0 0.32 0.76 2.50 3.63
1.41 -0.5 2.36 4.14 0.06 0.06 0 0 0.86 1.62 4.74 8.37
1.00 0.0 3.10 7.24 0.12 0.18 0.04 0.04 1.12 2.74 3.78 12.15
0.71 0.5 5.50 12.74 0.41 0.59 0.13 0.17 2.43 5.17 3.43 15.58
0.50 1.0 6.78 19.52 0.98 1.57 0.30 0.47 3.41 8.58 1.93 17.51
0.35 1.5 10.80 30.32 2.80 4.37 0.81 1.28 6.67 15.25 2.15 19.65
0.25 2.0 20.66 50.98 8.09 12.46 2.55 3.83 15.41 30.66 6.46 26.11
0.177 2.5 14.79 65.77 5.32 17.78 2.72 6.55 19.80 50.45 18.37 44.48
0.125 3.0 3.81 69.58 2.01 19.79 1.42 7.97 8.63 59.08 13.93 58.41
0.088 3.5 0.60 70.18 0.95 20.74 0.89 8.85 1.53 60.61 3.08 61.49
0.0625 4.0 0.60 70.78 1.09 21.83 1.17 10.02 1.17 61.78 2.05 63.55
Mud >4.0 29.22 100 78.17 100 89.98 100 38.22 100 36.45 100 173
Grain Size Sample 35-2.75 Sample 35-5.25 Sample 35-7.75 Sample 36-2.00 Sample 36-5.00
mm phi Ind. % Cum • ^ Ind. % Cum. % Ind. % Cum • /fk Ind. % Cum. % Ind. % Cum • ^
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0.07 0.07 0 0 0 0 0.21 0.21 0.13 0.13
2.00 -1.0 0 0.07 0 0 0 0 0.39 0.60 0.17 0.30
1.41 -0.5 0.10 0.17 0.06 0.06 0 0 0.24 0.84 0.59 0.89
1.00 0.0 0.12 0.29 0.04 0.10 0 0 0.39 1.23 0.81 1.70
0.71 0.5 0.17 0.46 0.06 0.16 0.05 0.05 1.24 2.47 0.91 2.61
0.50 1.0 0.19 0.65 0.06 0.22 0.11 0.16 6.59 9.06 0.72 3.33
0.35 1.5 0.43 1.08 0.32 0.54 0.48 0.64 16.26 25.32 0.61 3.94
0.25 2.0 1.87 2.95 1.73 2.27 3.03 3.67 23.46 48.78 0.59 4.53
0.177 2.5 5.85 8.79 8.48 10.74 9.36 13.03 12.71 61.49 0.62 5.15
0.125 3.0 11.79 20.59 18.04 28.78 15.09 28.12 1.90 63.39 0.98 6.13
0.088 3.5 9.44 30.02 6.50 35.27 7.78 35.90 1.03 64.42 1.26 7.39
0.0625 4.0 11.42 41.45 3.26 38.54 8.62 44.52 5.35 69.77 1.47 8.86
Mud >4.0 58.55 100 61.46 100 55.48 100 30.23 100 91.14 100
Grain Size Sample 37-3.00 Sample 37-6.00 Sample 37-7.50 Sample 38-0.50 Sample 38-3.50
mm phi Ind. % Cum • Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 12.81 12.81 30.34 30.34 16.55 16.55 0 0
2.83 -1.5 0.09 0.09 1.47 14.28 5.46 35.80 0 16.55 0 0
2.00 -1.0 0.02 0.11 0.91 15.19 3.45 39.26 0.23 16.78 0 0
1.41 -0.5 0.07 0.18 0.88 16.07 2.92 42.18 0 16.78 0 0
1.00 0.0 0.09 0.27 0.72 16.79 2.08 44.26 0.13 16.91 0 0
0.71 0.5 0.41 0.68 0.80 17.59 1.80 46.06 0.58 17.49 0 0
0.50 1.0 0.92 1.61 1.23 18.81 1.71 47.76 2.93 20.42 0.10 0.10
0.35 1.5 2.03 3.64 1.33 20.14 1.44 49.20 10.38 30.80 3.90 4.00
0.25 2.0 3.20 6.84 2.91 23.05 1.86 51.06 21.99 52.79 27.38 31.38
0.177 2.5 17.34 24.17 12.33 35.38 7.14 58.19 19.18 71.97 29.36 60.74
0.125 3.0 46.29 70.46 24.93 60.31 25.33 83.53 6.65 78.63 8.79 69.53
0.088 3.5 16.56 87.02 26.60 86.91 5.22 88.75 2.04 80.67 0.06 69.58
0.0625 4.0 2.77 89.79 2.35 89.26 0.94 89.69 0.65 81.32 0.62 70.20
Mud >4.0 10.21 100 10.74 100 10.31 100 18.68 100 29.80 100 174
Grain Size Sample 38-6.50 Sample 38-8.75 Sample 39-2.00 Sample 39-5.00 Sample 39-8.40
mm phi Ind. % Cum • % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • Á Ind. % Cum. %
4.00 -2.0 5.11 5.11 0 0 0 0 0 0 0.20 0.20
2.83 -1.5 0.60 5.71 0 0 0 0 0 0 0.58 0.78
2.00 -1.0 0.44 6.15 0 0 0.03 0.03 1.31 1.31 0.87 1.65
1.41 -0.5 0.36 6.51 0 0 0.04 0.07 0.17 1.49 2.15 3.80
1.00 0.0 0.25 6.76 0 0 0.15 0.22 0.41 1.90 4.18 7.98
0.71 0.5 0.19 6.94 0.01 0.01 0.36 0.58 1.01 2.91 6.90 14.88
0.50 1.0 0.16 7.11 0.08 0.09 1.16 1.74 3.06 5.97 13.84 28.72
0.35 1.5 1.90 9.01 4.59 4.68 2.55 4.29 6.12 12.09 23.16 51.88
0.25 2.0 11.34 20.35 44.57 49.25 4.77 9.06 8.25 20.34 20.31 72.19
0.177 2.5 11.55 31.90 42.79 92.04 6.89 15.95 10.29 30.63 9.01 81.20
0.125 3.0 4.61 36.51 5.02 97.06 3.99 19.94 5.25 35.88 3.13 84.33
0.088 3.5 0.47 36.98 0.14 97.20 15.87 35.81 6.00 41.88 1.39 85.72
0.0625 4.0 0.27 37.25 0.01 97.21 16.53 52.34 9.53 51.41 1.03 86.75
Mud >4.0 62.75 100 2.79 100 47.66 100 48.59 100 13.25 100
Grain Size Sample 40-8.00 Sample 41-2.50 Sample 41-4.75 Sample 41-7.00 Sample 44-2.00
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 0.59 0.59 0.50 0.50 2.20 2.20 0 0
2.83 -1.5 0 0 0.32 0.91 0.34 0.84 0 2.20 0 0
2.00 -1.0 0.08 0.08 0.75 1.66 0.04 0.88 0 2.20 0 0
1.41 -0.5 0.08 0.16 0.49 2.15 0.32 1.20 0 2.20 0 0
1.00 0.0 0 0.16 0.58 2.73 0.29 1.49 0.03 2.23 0 0
0.71 0.5 0.01 0.17 1.32 4.05 0.93 2.42 0.17 2.39 0 0
0.50 1.0 0.11 0.28 3.89 7.94 3.70 6.12 1.95 4.34 0 0
0.35 1.5 2.03 2.31 8.75 16.69 12.07 18.19 11.68 16.02 0 0
0.25 2.0 9.30 11.61 27.15 43.84 36.41 54.60 37.21 53.24 0 0
0.177 2.5 11.54 23.15 33.65 77.49 26.93 81.53 31.18 84.42 0 0
0.125 3.0 3.88 27.03 9.40 86.89 6.10 87.63 5.79 90.21 0 0
0.088 3.5 0.24 27.27 0.74 87.63 1.25 88.88 0.69 90.89 0 0
0.0625 4.0 0.13 27.40 0.21 87.85 0.72 89.60 0.30 91.19 2.76 2.76
Mud >4.0 72.60 100 12.15 100 10.40 100 8.81 100 97.24 100 175
Grala Size Sample 44-5.00 Sample 45-1.00 Sample 45-3.00 Sample 45-4.00 Sample 45-5.50
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum • % Ind. % Cum. % Ind. % Cum •
4.00 -2.0 0 0 0 0 0.89 0.89 0 0 0.14 0.14
2.83 -1.5 0 0 0.63 0.63 0.59 1.48 0.74 0.74 0.96 1.10
2.00 -1.0 0 0 2.24 2.87 1.85 3.33 0.96 1.70 1.69 2.79
1.41 -0.5 0 0 4.46 7.33 1.96 5.29 1.47 3.17 3.21 6.00
1.00 0.0 0 0 4.03 11.36 2.14 7.43 1.52 4.69 2.64 8.64
0.71 0.5 0.01 0.01 3.74 15.09 2.42 9.85 2.44 7.13 3.54 12.18
0.50 1.0 0.02 0.03 2.96 18.05 5.41 15.26 4.89 12.01 8.79 20.97
0.35 1.5 0.04 0.07 3.90 21.95 13.12 28.37 14.88 26.89 20.68 41.65
0.25 2.0 0.85 0.92 5.70 27.65 22.02 50.39 24.95 51.84 28.91 70.56
0.177 2.5 13.92 14.84 8.46 36.11 16.38 66.77 12.87 64.71 11.31 81.87
0.125 3.0 37.67 52.51 13.43 59.54 7.65 74.42 5.22 69.94 3.84 85.71
0.088 3.5 3.70 56.21 3.75 53.29 1.68 76.10 1.69 71.63 1.10 86.81
0.0625 4.0 0.73 56.94 1.83 55.13 0.99 77.09 0.89 72.52 0.69 87.50
Mud >4.0 43.06 100 44.87 100 22.91 100 27.48 100 12.50 100
Grain Size Sample 46-0.75 Sample 46-2.50 Sample 46-5.50 Sample 47-0.50 Sample 47-2.75
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum • /ti Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0.57 0.57 0 0 0 0 0 0 0 0
2.83 -1.5 1.43 2.00 0.13 0.13 0.09 0.09 0 0 0 0
2.00 -1.0 3.33 5.33 0.09 0.22 0.08 0.17 0 0 0 0
1.41 -0.5 6.18 11.52 0.07 0.29 0.42 0.58 0 0 0 0
1.00 0.0 4.31 15.83 0.06 0.35 0.77 1.35 0.04 0.04 0 0
0.71 0.5 4.89 20.72 0.13 0.38 2.48 3.83 0.02 0.06 0.01 0.01
0.50 1.0 3.44 24.16 0.61 1.08 13.19 17.02 0.03 0.09 0.01 0.02
0.35 1.5 3.79 27.95 2.68 3.76 38.35 55.37 0.13 0.22 0.01 0.03
0.25 2.0 5.69 33.64 32.07 35.83 21.71 77.08 0.47 0.69 0.02 0.04
0.177 2.5 9.94 43.58 44.84 80.67 7.45 84.53 0.84 1.53 0.06 0.10
0.125 3.0 13.98 57.56 5.90 86.58 3.29 87.82 2.03 3.56 1.67 1.77
0.088 3.5 3.66 61.22 0.30 86.88 0.92 88.74 7.96 11.52 9.84 11.62
0.0625 4.0 1.87 63.09 0.10 86.98 0.42 89.16 6.24 17.76 9.37 20.99
Mud >4.0 36.01 100 13.02 100 10.84 100 82.24 100 79.01 100 176
Grain size Sample 47-5.00 Sample 47-7.25 Sample 47-8.50 Sample 48-2.00 Sample 48-5.00
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. 7, Cum • Ái
4.00 -2.0 0 0 4.98 4.98 0 0 0.20 0.20 0 0
2.83 -1.5 0 0 0 4.98 0 0 0.29 0.49 0 0
2.00 -1.0 0.03 0.03 0.16 5.14 0 0 0.17 0.66 0.08 0.08
1.41 -0.5 0.02 0.05 0.14 5.28 0.05 0.05 0.21 0.87 0.10 0.18
1.00 0.0 0.01 0.06 0.06 5.35 0.07 0.12 0.27 1.14 0.09 0.27
0.71 0.5 0.01 0.07 0.05 5.40 0.08 0.21 0.43 1.57 0.17 0.44
0.50 1.0 0.01 0.08 0.03 5.43 0.09 0.30 0.83 2.40 0.25 0.69
0.35 1.5 0.02 0.10 0.02 5.45 0.14 0.44 1.30 3.70 0.47 1.16
0.25 2.0 0.03 0.13 0.02 5.47 0.22 0.66 1.82 5.53 1.08 2.24
0.177 2.5 0.11 0.24 0.04 5.51 0.42 1.08 11.67 17.20 14.67 16.91
0.125 3.0 2.59 2.83 1.12 6.63 3.12 4.20 52.80 70.00 58.27 75.18
0.088 3.5 10.90 13.72 9.49 16.12 21.32 25.52 13.85 83.85 12.74 87.92
0.0625 4.0 10.58 24.30 8.08 24.20 9.74 35.26 2.08 85.92 2.13 90.05
Mud >4.0 75.70 100 75.80 100 64.74 100 14.08 100 9.95 100
Grain Size Sample 48-7.75 Sample 49-1.75 Sample 49-4.75 Sample 49-7.75 Sample 50-2.50
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • ^
4.00 -2.0 0.40 0.40 0 0 0 0 0 0 9.18 9.18
2.83 -1.5 0 0.40 0 0 0 0 0 0 5.15 14.33
2.00 -1.0 0.21 0.61 0 0 0 0 0 0 3.80 18.13
1.41 -0.5 0.35 0.96 0 0 0 0 0 0 3.73 21.86
1.00 0.0 0.38 1.34 0 0 0 0 0.01 0.01 2.56 24.43
0.71 0.5 0.59 1.93 0 0 0 0 0.01 0.02 3.54 27.97
0.50 1.0 0.96 2.89 0.02 0.02 0 0 0.01 0.02 4.47 32.44
0.35 1.5 1.34 4.23 0.02 0.04 0.01 0.01 0.02 0.04 9.10 41.54
0.25 2.0 2.04 6.27 0.05 0.09 0.01 0.02 0.05 0.09 17.30 58.84
0.177 2.5 6.78 13.05 0.37 0.46 0.13 0.15 0.31 0.40 14.94 73.78
0.125 3.0 32.18 45.23 9.77 10.23 5.25 5.40 7.65 8.05 5.07 78.05
0.088 3.5 21.96 67.19 41.75 51.98 21.57 26.97 27.14 35.19 0.82 79.67
0.06251 4.0 5.64 72.83 15.67 67.65 15.65 42.62 21.32 56.51 0.41 80.08
Mud >4.0 27.17 100 32.35 100 57.38 100 43.49 100 19.92 100
Grain Size Sample 50-3.25 Sample 50-5.75 Sample 50-8.25 Sample 51-2.00 Sample 51-5.00
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 4.52 4.52 0 0 0 0 2.12 2.12 0 0
2.83 -1.5 2.66 7.18 0 0 0 0 0 2.12 0 0
2.00 -1.0 1.98 9.16 0 0 0 0 0 2.12 0 0
1.41 -0.5 2.29 11.45 0 0 0 0 0.02 2.14 0 0
1.00 0.0 1.41 12.86 0 0 0 0 0.02 2.16 0.02 0.02
0.71 0.5 1.57 14.43 0.01 0.01 0 0 0.02 2.18 0.10 0.12
0.50 1.0 2.99 17.42 0.02 0.03 0.01 0.01 0.12 2.30 0.31 0.43
0.35 1.5 9.72 27.14 0.04 0.07 0.01 0.02 0.90 3.20 1.56 1.99
0.25 2.0 23.67 50.81 0.10 0.17 0.04 0.06 10.97 14.17 8.66 10.65
0.177 2.5 23.14 73.95 0.46 0.63 0.78 0.84 38.89 53.07 29.43 40.08
0.125 3.0 10.31 84.26 1.91 2.54 3.35 4.19 22.56 75.63 26.89 66.97
0.088 3.5 1.23 85.49 1.05 3.59 1.84 6.03 2.97 78.60 4.62 71.59
0.0625 4.0 0.41 85.90 0.64 4.23 1.56 7.59 1.26 79.86 1.59 73.18
Mud >4.0 14.10 100 95.77 100 92.41 100 20.14 100 26.82 100
Grain Size Sample 51-8.00 Sample 52-3.75 Sample 53-1.50 Sample 53-3.75 Sample 53-6.00
mm phi Ind. % Cum ? % Ind. % Cum • % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • /o
4.00 -2.0 0 0 0 0 0.34 0.34 0 0 0.85 0.85
2.83 -1.5 0 0 0 0 0.22 0.56 0 0 0.51 1.36
2.00 -1.0 0 0 0.09 0.09 0.35 0.91 0.56 0.56 0.83 2.19
1.41 -0.5 0 0 0.05 0.14 1.18 2.09 0.23 0.79 1.06 3.25
1.00 0.0 0 0 0.02 0.16 2.00 2.09 0.38 1.17 1.04 4.29
0.71 0.5 0.13 0.13 0.07 0.23 5.23 9.32 1.55 2.72 2.31 6.60
0.50 1.0 0.56 0.69 0.10 0.33 10.91 20.23 3.26 5.98 5.02 11.62
0.35 1.5 3.12 3.81 0.15 0.48 15.44 35.67 4.99 10.96 7.74 19.36
0.25 2.0 13.41 17.22 0.12 0.60 12.40 48.07 8.83 19.79 10.07 29.44
0.177 2.5 21.12 38.34 0.25 0.85 8.35 56.42 18.65 38.44 14.49 43.93
0.125 3.0 13.55 51.89 1.32 2.17 4.36 60.78 25.29 63.73 15.86 59.79
0.088 3.5 7.78 59.67 2.20 4.36 1.22 62.00 9.75 73.48 6.77 66.56
0.0625 4.0 2.90 62.57 3.42 7.78 0.92 62.92 2.52 76.00 3.08 69.64
Mud >4.0 37.43 100 92.22 100 37.08 100 24.00 100 30.36 100 178
Grain Size Sample 58-2.25 Sample 58-4.25 Sample 58-6.25 Sample 58-8.25 Sample 59-6.50
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum • ^
4.00 -2.0 0 0 0 0 0 0 1.18 1.18 0.25 0.25
2.83 -1.5 0 0 0 0 0 0 0 1.18 0.74 0.99
2.00 -1.0 0.15 0.15 0 0 0 0 0.20 1.38 0.23 1.22
1.41 -0.5 0.03 0.18 0 0 0.07 0.07 0.01 1.39 0.12 1.34
1.00 0.0 0.29 0.47 0 0 0.06 0.13 0.04 1.42 0.09 1.43
0.71 0.5 1.25 1.71 0 0 0.13 0.26 0.05 1.47 0.04 1.47
0.50 1.0 3.60 5.31 0 0 0.52 0.78 0.23 1.70 0.03 1.50
0.35 1.5 6.37 11.68 0 0 5.99 6.77 4.24 5.94 0.04 1.54
0.25 2.0 36.43 48.11 0 0 56.45 63.22 34.24 40.18 0.09 1.63
0.177 2.5 39.65 87.76 0 0 38.71 91.93 44.54 84.72 0.25 1.88
0.125 3.0 6.12 94.37 0 0 3.03 94.96 5.67 90.39 1.27 3.15
0.088 3.5 0.61 94.98 0 0 0.35 95.31 0.30 90.69 6.06 9.21
0.0625 4.0 0.22 95.20 2.75 2.75 0.13 95.44 0.09 90.78 7.36 16.57
Mud >4.0 4.80 100 97.25 100 4.56 100 9.22 100 83.43 100
Grain Size Sample 59-7.75 Sample 60-1.50 Sample 60-4.00 Sample 60-6.25 Sample 62-3.75
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum • % Ind. % Cum • % Ind. % Cum. %
4.00 -2.0 0 0 0.84 0.84 0.22 0.22 0.19 0.19 0 0
2.83 -1.5 0.09 0.09 0.87 1.71 0.10 0.32 0.14 0.33 0 0
2.00 -1.0 0.09 0.18 0.35 2.06 0.48 0.80 0.09 0.42 0 0
1.41 -0.5 0.21 0.39 0.29 2.35 0.36 1.16 0.44 0.86 0 0
1.00 0.0 0.32 0.72 0.21 2.56 1.03 2.19 3.05 3.91 0 0
0.71 0.5 0.42 1.14 0.79 3.36 3.47 5.66 14.77 18.68 0 0
0.50 1.0 1.13 2.27 1.50 4.86 4.85 10.51 17.98 36.65 0.04 0.04
0.35 1.5 6.89 9.16 1.18 6.04 2.99 13.50 8.68 45.33 0.02 0.06
0.25 2.0 21.30 30.45 3.77 9.81 3.60 17.10 4.06 49.39 0.01 0.07
0.177 2.5 23.00 53.45 24.67 34.48 13.87 30.98 3.85 53.24 0.03 0.10
Q.125 3.0 21.93 75.38 29.69 64.17 12.69 43.67 1.74 54.98 0.07 0.17
0.088 3.5 4.37 79.75 3.46 67.63 1.98 45.65 0.66 55.64 0.17 0.34
0.0625 4.0 1.00 80.75 2.28 69.91 1.88 47.53 0.99 56.63 0.42 0.76
Mud >4.0 19.25 100 30.09 100 52.47 100 43.37 100 99.24 100 179
Grain Size Sample 62-5.50 Sample 63-0.75 Sample 63-2.00 Sample 64-3.50 Sample 64-5.75
mm phi Ind. % Ctim • % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 0 0 1.70 1.70 0.63 0.63 0 0
2.83 -1.5 0 0 0 0 1.13 2.83 0.44 1.07 0 0
2.00 -1.0 0 0 0 0 1.89 4.72 0.71 1.78 0.05 0.05
1.41 -0.5 0 0 0 0 2.52 7.24 0.81 2.59 0.07 0.12
1.00 0.0 0 0 0.10 0.10 1.84 9.09 0.74 3.33 0.12 0.24
0.71 0.5 0 0 0.07 0.17 2.09 11.18 0.74 4.07 0.26 0.50
0.50 1.0 0 0 0.54 0.71 2.37 13.55 0.91 4.98 0.45 0.95
0.35 1.5 0 0 3.75 4.46 5.85 19.40 1.98 6.95 1.02 1.97
0.25 2.0 0.01 0.01 3.70 8.16 5.45 24.85 5.23 12.18 4.24 6.21
0.177 2.5 0.03 0.04 5.14 13.30 6.76 31.61 11.91 24.09 14.05 20.26
0.125 3.0 0.06 0.10 4.44 17.74 8.95 40.56 16.55 40.65 32.34 52.60
0.088 3.5 0.22 0.32 3.13 20.87 4.98 45.54 8.37 49.02 14.11 66.71
0.0625 4.0 0.99 1.31 3.26 24.13 4.54 50.08 8.39 57.41 4.57 71.28
Mud >4.0 98.69 100 75.87 100 49.92 100 42.59 100 28.72 100
Grain Size Sample 67-3.50 Sample 67-6.50 Sample 70-1.50 Sample 71-0.50 Sample 91-3.50
mm phi Ind. % Cum • % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0.05 0.05 0 0 0 0
2.00 -1.0 0 0 0 0 0 0.05 0 0 0 0
1.41 -0.5 0 0 0 0 0.06 0.11 0 0 0.04 0.04
1.00 0.0 0.03 , 0.03 0 0 0.05 0.16 0.73 0.73 0.27 0.31
0.71 0.5 0.07 0.10 0.01 0.01 0.02 0.18 1.34 2.07 2.92 3.23
0.50 1.0 0.44 0.54 0.06 0.07 0.03 0.21 2.13 4.20 7.90 11.13
0.35 1.5 1.51 2.04 0.25 0.32 0.07 0.28 2.39 6.59 6.40 17.53
0.25 2.0 4.39 6.43 0.83 1.15 0.16 0.44 3.38 9.97 6.14 23.67
0.177 2.5 7.29 13.72 2.30 3.45 0.33 0.77 8.00 17.97 15.65 39.32
0.125 3.0 15.25 28.97 9.07 12.52 0.18 0.95 11.90 29.87 25.66 64.98
0.088 3.5 37.59 66.56 35.70 48.22 0.33 1.28 2.92 32.79 11.89 76.87
0.06251 4.0 11.08 77.65 21.62 69.84 2.41 3.69 1.65 34.45 3.77 80.64
Mud >4.0 22.35 100 30.16 100 96.31 100 65.55 100 19.36 100
180
Grain Size Sample 100-8.60 Sample 108-2.75 Sample 108-3.75 Sample 108-5.00 Sample 109-1.50
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum m /a
4.00 -2.0 0 0 0 0 0 0 5.01 5.01 0 0
2.83 -1.5 0 0 0 0 0 0 0 5.01 0 0
2.00 -1.0 0 0 1.54 1.54 3.83 3.83 1.84 6.85 0.27 0.27
1.41 -0.5 0.05 0.05 0.44 1.98 1.84 5.67 0.88 7.73 0.52 0.79
1.00 0.0 0.13 0.18 0.36 2.34 2.12 7.79 1.00 8.73 0.84 1.63
0.71 0.5 0.16 0.34 0.24 2.58 1.94 9.72 1.15 9.88 2.13 3.76
0.50 1.0 0.11 0.45 0.22 2.81 1.78 11.50 1.30 11.18 4.80 8.56
0.35 1.5 0.09 0.54 0.31 3.12 2.58 14.08 1.83 13.01 7.70 16.26
0.25 2.0 0.50 1.04 1.93 5.05 11.58 25.66 5.98 18.99 14.29 30.55
0.177 2.5 5.53 6.56 5.52 10.57 22.30 47.96 9.10 28.09 26.09 56.64
0.125 3.0 38.13 44.69 7.25 17.82 9.28 57.24 11.10 39.19 14.18 70.82
0.088 3.5 10.10 54.79 2.70 20.52 2.25 59.49 3.90 43.09 1.97 72.78
0.0625 4.0 0.80 55.59 1.70 22.22 1.05 60.55 1.96 45.06 0.87 73.65
Mud >4.0 44.01 100 77.78 100 39.45 100 54.94 100 26.35 100
Grain Size Sample 109-3.00 Sample 109-4.50 Sample 109-5.75 Sample 110-1.00 Sample 110-4.64
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0 0 0 0 0 0
2.00 -1.0 0.16 0.16 0.20 0.20 6.16 6.16 0 0 0.04 0.04
1.41 -0.5 0.12 0.28 0.46 0.66 2.84 9.00 0.11 0.11 0.05 0.09
1.00 0.0 0.36 0.64 0.54 1.20 2.43 11.43 0.27 0.38 0.11 0.20
0.71 0.5 1.03 1.67 1.09 2.29 2.11 13.54 0.64 1.02 0.08 0.28
0.50 1.0 3.77 5.44 2.18 4.47 1.92 15.46 1.40 2.43 0.08 0.36
0.35 1.5 6.63 12.07 3.44 7.91 2.26 17.72 1.79 4.22 0.07 0.43
0.25 2.0 9.11 21.18 6.41 14.32 3.84 21.56 1.86 6.08 0.18 0.61
0.177 2.5 20.04 41.22 16.87 31.19 10.63 32.19 4.31 10.39 0.55 1.16
0.125 3.0 25.98 67.20 25.91 57.10 17.30 49.49 36.43 46.82 6.05 7.21
0.088 3.5 3.29 70.49 8.20 65.30 5.75 55.24 39.14 85.96 31.00 38.21
0.06251 4.0 0.61 71.10 1.86 67.16 1.59 56.83 5.21 91.17 25.39 63.60 00
Mud >4.0 28.90 100 32.84 100 43.17 100 8.83 100 36.40 100
Grain Size Sample 91-5.50 Sample 92-4.00 Sample 92-5.50 Sample 96-1.50 Sample 96-3.50
mm phi Ind. % Cum • Ind. % Cum « % Ind. % Cum. % Ind. % Cum • Ind. % Cum. %
4.00 -2.0 0 0 0.25 0.25 0.04 0.04 1.56 1.56 0 0
2.83 -1.5 0 0 0 0.25 0 0.04 0 1.56 0 0
2.00 -1.0 0 0 0.09 0.34 0.02 0.06 0.62 2.18 0 0
1.41 -0.5 0.03 0.03 0.18 0.52 0.04 0.10 0.40 2.58 0 0
1.00 0.0 0.06 0.09 3.04 3.56 1.89 1.99 0.80 3.38 0 0
0.71 0.5 0.19 0.28 12.81 16.37 10.77 12.76 1.52 4.90 0.09 0.09
0.50 1.0 0.39 0.67 39.06 55.43 38.55 51.31 2.52 7.42 0.28 0.37
0.35 1.5 0.43 1.10 24.09 79.52 40.11 91.42 3.12 10.54 0.61 0.98
0.25 2.0 0.43 1.53 1.88 81.40 1.60 93.02 5.18 15.72 1.86 2.84
0.177 2.5 1.52 3.05 1.15 82.55 0.39 93.41 11.56 27.28 4.97 7.81
0.125 3.0 10.20 13.25 1.48 84.03 0.31 93.72 27.31 54.59 13.31 21.12
0.088 3.5 46.64 59.89 1.26 85.29 0.16 93.88 17.66 72.25 32.40 53.53
0.0625 4.0 18.35 78.24 0.77 86.06 0.10 93.98 3.82 16.01 16.05 69.58
Mud >4.0 21.76 100 13.94 100 6.02 100 23.93 100 30.42 100
Grain Size Sample 96-5.50 Sample 97-0.50 Sample 97-2.50 Sample 97-4.50 Sample 97-6.50
mm phi Ind. % Cum. % Ind. % Cum. % Ind. % Cum. % Ind. % Cum. 7. Ind. % Cum. %
4.00 -2.0 0 0 0 0 0 0 0 0 0 0
2.83 -1.5 0 0 0 0 0 0 0 0 0 0
2.00 -1.0 0 0 0.03 0.03 0 0 0 0 0 0
1.41 -0.5 0.01 0.01 0.14 0.17 0.05 0.05 0.03 0.03 0 0
1.00 0.0 0.05 0.06 0.21 0.38 0.07 0.12 0.01 0.04 0 0
0.71 0.5 0.12 0.18 0.29 0.67 0.09 0.21 0.02 0.06 0.01 0.01
0.50 1.0 0.28 0.46 0.33 1.00 0.15 0.36 0.04 0.10 0.02 0.03
0.35 1.5 0.59 1.05 0.40 1.40 0.21 0.57 0.04 0.14 0.02 0.05
0.25 2.0 1.48 2.53 0.59 1.99 0.33 0.90 0.06 0.20 0.05 0.10
0.177 2.5 3.07 5.60 1.01 3.00 0.93 1.83 0.15 0.35 0.23 0.33
0.125 3.0 7.65 13.25 6.65 9.65 8.05 9.88 1.24 1.59 4.21 4.54
0.088 3.5 24.57 37.82 19.95 29.60 30.59 40.48 13.93 15.52 17.33 21.87
0.0625Í 4.0 21.05 58.87 21.00 50.60 20.26 60.74 18.28 33.80 11.82 33.69 182
Mud >4.0 41.13 100 49.40 100 39.26 100 66.20 100 66.31 100
Grain Size Sample 111-0.50 Sample 111-2.50 Sample 111-4.25 Sample 111-5.50 Sample 111-6.25
mm phi Ind. Z Cum. % Ind. % Cura. % Ind. % Cum. % Ind. % Cum • Á Ind. % Cum. Z
4.00 -2.0 49.61 49.61 10.05 1Ó.05 2.32 2.32 0.26 0.26 11.48 11.48
2.83 -1.5 3.04 52.65 2.51 12.56 0.96 3.28 1.31 1.57 6.36 17.84
2.00 -1.0 2.88 55.53 4.22 16.78 3.04 6.32 0.97 2.54 7.04 24.88
1.41 -0.5 3.23 58.75 5.90 22.68 5.35 11.67 1.48 4.02 8.65 33.53
1.00 0.0 3.03 61.78 5.41 28.09 7.72 19.39 1.40 5.42 8.36 41.88
0.71 0.5 3.58 65.36 4.50 32.59 10.21 29.60 3.11 8.53 6.84 48.72
0.50 1.0 3.91 69.27 3.88 36.47 12.20 41.80 4.61 13.14 4.92 53.64
0.35 1.5 3.83 73.10 3.85 40.32 12.44 54.24 5.76 18.90 4.00 57.64
0.25 2.0 2.97 76.07 4.62 44.94 9.40 63.64 6.67 25.57 4.35 61.99
0.177 2.5 1.50 76.07 2.59 47.53 3.77 67.41 6.30 31.87 4.06 66.05
0.125 3.0 1.29 78.87 1.22 48.75 2.46 69.87 5.54 37.41 2.97 69.02
0.088 3.5 0.82 79.68 1.06 49.81 1.74 71.61 4.12 41.53 2.13 71.15
0.0625 4.0 0.57 80.25 2.53 52.34 0.98 72.59 2.98 44.51 1.40 72.56
Mud >4.0 19.75 100 47.66 100 24.41 100 55.49 100 27.44 100
Grai n Size Sample 111-7.50 Sample 111-8.00 Sample 113-0.50 Sample 113-1.50 Sample 114-5.75
mm phi Ind. % Cum • ^ Ind. % Cura. % Ind. % Cum. % Ind. % Cum. Z Ind. Z Cum. %
4.00 -2.0 0 0 17.51 17.51 0 0 0 0 0 0
2.83 -1.5 0 0 7.93 25.44 0 0 0 0 0 0
2.00 -1.0 4.49 4.49 10.34 35.78 0.07 0.07 0 0 0 0
1.41 -0.5 2.52 7.01 10.86 46.64 0.07 0.14 0 0 0.09 0.09
1.00 0.0 2.06 9.07 8.22 54.87 0.12 0.26 0.08 0.08 0.20 0.29
0.71 0.5 2.02 11.09 5.67 60.54 0.24 0.50 0.10 0.18 0.45 0.74
0.50 1.0 1.99 13.08 3.61 64.15 0.40 0.90 0.24 0.42 1.65 2.39
0.35 1.5 2.59 15.67 2.71 66.85 0.50 1.40 0.32 0.74 5.19 7.58
0.25 2.0 4.73 20.40 2.72 69.57 0.92 2.32 0.53 1.27 6.43 14.01
0.177 2.5 5.99 26.39 1.82 71.39 1.30 3.62 0.92 2.19 12.29 26.30
0.125 3.0 5.91 32.30 1.22 72.61 4.58 8.20 4.59 6.77 17.07 43.37
0.088 3.5 4.47 36.77 1.07 73.68 33.44 41.64 38.76 45.53 5.15 48.52
0.06251 4.0 3.16 39.93 0.74 74.42 14.45 56.09 19.79 65.32 4.46 52.99
Mud >4.0 60.07 100 25.58 100 43.91 100 34.68 100 47.01 100 183
Grain Size Sample 114-7.50 Sample 115-5.00 Sample 115-5.50 Sample 115-7.
mm phi Ind. % CuiD • % Ind. % Chid • % Ind. % Cum • % Ind. % Cum.
4.00 -2.0 0 0 8.59 8.59 0.91 0.91 0.40 0.40
2.83 -1.5 0 0 4.09 12.68 0.34 1.25 0 0.40
2.00 -1.0 0.24 0.24 4.87 17.55 0.34 1.60 0.38 0.78
1.41 -0.5 0.10 0.34 5.51 23.06 0.62 2.22 0.18 0.96
1.00 0.0 0.18 0.52 4.09 27.15 0.72 2.94 0.23 1.19
0.71 0.5 0.50 1.02 4.31 31.46 0.86 3.80 0.49 1.68
0.50 1.0 1.00 2.02 4.37 35.83 1.24 5.04 1.00 2.68
0.35 1.5 2.28 4.30 5.43 41.26 2.69 7.73 2.09 4.77
0.25 2.0 5.35 9.65 9.07 50.33 7.37 15.10 6.04 10.81
0.177 2.5 14.73 24.37 13.53 63.86 18.09 33.19 14.18 24.99
0.125 3.0 25.71 50.08 12.78 76.64 29.21 62.40 26.98 51.97
0.088 3.5 5.41 55.50 3.09 79.73 7.69 70.09 17.99 69.96
0.0625 4.0 3.36 58.86 1.19 80.91 2.44 72.53 6.04 76.00
Mud >4.0 41.14 100 19.09 100 27.47 100 24.00 100
Grain Size Sample 131-3.75 Sample 131-4.75 Sample 131-5.75
mm phi Ind. % Cum. % Ind. % Com • % Ind. % Cum • %
4.00 -2.0 2.29 2.29 1.07 1.07 0 0
2.83 -1.5 0 2.29 0 1.07 0 0
2.00 -1.0 4.17 6.46 2.39 3.46 5.32 5.32
1.41 -0.5 4.51 10.97 2.77 6.23 3.64 8.96
1.00 0.0 4.28 15.25 3.24 9.46 4.65 13.61
0.71 0.5 4.61 19.86 4.78 14.24 5.18 18.79
0.50 1.0 5.52 25.38 6.21 20.45 6.65 25.44
0.35 1.5 6.62 32.00 7.64 28.09 6.08 31.52
0.25 2.0 9.12 41.12 10.22 38.30 9.91 41.43
0.177 2.5 9.01 50.13 13.88 52.18 13.25 54.68
0.125 3.0 11.17 61.30 11.72 63.90 11.09 65.77
0.088 3.5 3.32 64.62 3.67 67.57 3.77 69.54
0.0625 4.0 1.47 66.08 1.59 69.16 1.70 71.24
Mud >4.0 33.92 100 30.84 100 28.76 100 184