Michael E. Lyle. CLAY MINERALOGY OF THE FUNGO RIVER
FORMATION, ONSLOW BAY, NORTH CAROLINA CONTINENTAL SHELF.
(Under the direction of Dr. Stanley R. Riggs) Department of
Geology, May 1984.
ABSTRACT
The Fungo River Formation in Onslow Bay, North Carolina
consists of the Burdigalian (late early Miocene), Langhian
(early middle Miocene), and the Serravallian (middle Miocene)
depositional sequences as defined by seismic stratigraphy and
biostratigraphy. X-ray diffraction analyses have defined the
clay mineral composition of these sequences as follows:
Serravallian Montmorillonite 50 to 70%
(BBF Depositional Illite 25 to 40%
Sequence ) Chamo site 1 to 10 %
Sepiolite not detectable
Langhian Montmorillonite 6 to 45%
(AF Depositional Illite 41 to 89%
Sequence) Sepiolite 3 to 18%
Chamo site not detectable
Burdigalian Montmorillonite 25 to 70%
(FFF Depositional Illite 27 to 70%
Sequence) Chamo site 0 to 2 4%
Sepiolite 3 to 18%
Clinoptilolite, a zeolite mineral, is present
infrequently in the Burdigalian, not detectable in the
Langhian, and present throughout the Serravallian. Well
crystallized, mica-derived montmorillonite and a poorly
crystallized illite are interpreted to be of terrigenous
origin. Sepiolite, chamosite, and a glauconitic illite, are
interpreted to be of authigenic origin Clinoptilolite is
interpreted to be authigenic in the Burdigallian sediments
and detrital in the Serrava11ian. The diagenetic alteration
of clays and formation of zeolite is thought to be related to
variations in availability of Fe, Mg, and silica in response
to changing climatic conditions, weathering processes, and
sea-level fluctuations.
CLAY MINERALOGY OF THE PUNGO RIVER FORMATION,
ONSLOW BAY, NORTH CAROLINA CONTINENTAL SHELF
A Thesis
Presented to
the Graduate Faculty of the Department of Geology
East Carolina University
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Geology
by
Michael E. Lyle
May, 1984
J. T. JÜYNJEB UBRAJiT
«AST GABOUNA UNIVBRSTTT
clay mineralogy of the fungo river formation
ONSLOW BAY, NORTH CA-ROLINA CONTINENTAL SHELF
by
Michael E. Lyle
.APPROVED BY:
DIRECTOR OF THESIS
CONÎM1TTEE MEMBER
C01ÎMITTEE MEMBER
Dr. Donald W. Neal
DEAN OF THE GRADUATE SCHOOL
ACKNOWLEDGEMENTS
Successful mission accomplishment depends not only on
those who carry out a task, but on the support personnel as
well. I would like to express my gratitude to Dr. Stanley
Riggs, mentor, chief cook and bottlewasher of this thesis,
and to Drs. Charles Brown, Donald Neal, and Lee Otte,
committee members. Dr. Dennis Darby of Old Dominion
University served as outside reader. I am indebted to Dr.
Richard Spruill, Mary Paula Brown, Brian Gray, Jim Watson,
Lori Stewart, Sue Oppenlander, Robert Privette, Dare Merritt,
Richard Levinson, Leo Fay, and all of my friends and
colleagues, here and in Alaska, for their support and
encouragement during this mission. Last but certainly not
least, I would like to thank the "primary support personnel,"
my parents, for without them, I could not even have made it
to the Line of Departure, much less the objective.
TABLE OF CONTENTS
Page
INTRODUCTION
Regional Setting 1
Previous Work 4
Objectives 6
GEOLOGIC SETTING
Structure 8
Stratigraphy 10
PROCEDURES
Sampling 14
Laboratory Analysis 16
RESULTS
Textural Analysis 30
Petrographic Analysis 34
Clay Mineral Analysis ..... 45
DISCUSSION 57
CONCLUSIONS 81
REFERENCES CITED 84
APPENDIX A 92
APPENDIX B 99
APPENDIX C 101
APPENDIX D 108
APPENDIX E no
APPENDIX F 112
APPENDIX G 121
APPENDIX H 125
LIST OF FIGURES
FIGURE Fage
1 Location map of structural and topographic
features in the Onslow Bay area 9
2 Miocene seismic units of Onslow Bay and
their lithology 12
3 Location map showing 1) outcrop belt of the
Fungo River Formation across Onslow Bay; 2)
the 3 depositional sequences of the Fungo
River Formation defined by seismic strati-
graphy; 3) 15 of the 18+ depositional units
defined by seismic stratigraphy; and 4) the
location of vibracore holes used in this
study 13
4 Flowchart of procedures used to accomplish
the laboratory procedures 17
5 Flowchart of routine treatments to the finer
than 8 phi material of all samples 20
6 Graph showing the relationship of precision
error in clay analysis procedures to mean
clay percent 26
7a Diagram illustrating the method for determin-
ing the crystallinity of smectite. ..... 27
7b Diagram illustrating the method for determin-
ing the crystallinity of illite 27
8 Ternary diagram summarizing sand-si1t-clay
percentages for the Burdigalian, Langhian,
and Serravallian depositional sequences. . . 32
9 X-ray diffractograms showing basal peak
responses to routine treatments as well as
LiCl-DMSO treatment 49
Q
10 7A d-spacing of two samples showing poorly
crystallized and well crystallized peaks . 53
1 1 X-ray diffractogram showing peak responses
to heat treatments 54
1 2 Flowchart showing paragenetic sequence of the
clay-zeolite suite in the Fungo River Forma-
tion of Aurora according to Rooney (1965) . . 58
Figure Page
13 A generalized model for continental clay
mineral formation during warm and cold
climatic regimes. ... 64
14 Plot of average smectite and illite percent-
ages in each of the sampled Pungo River
Formation units 66
15 Global cycles of relative sea level change,
during the early to middle Miocene 67
16 Cycle of dissolved silica in the oceans ... 76
17 Generalized trends of clay mineral and zeolite
distribution in Miocene sediments in the S.E.
United States 79
18 Plot of presence and absence of c1inopti1o1ite
and sepiolite in the three depositional sequen-
ces of the Pungo River Formation of Onslow
Bay 80
LIST OF TABLES
Table Page
1 Vibracores and the sediment samples used
in this study, along with their depth below
the sediment surface 15
2 Routine instrument settings for the x-ray
analyses conducted on a General Electric
XRD-6 Diffractometer 24
3 Summary of textural data for the 3 depositional
sequences in the Rungo River Formation, Onslow
Bay 31
4 Summary characteristics of mineral grain types
found in the thin section study 35
5 Total clay, percentages of specific clay minerals
and crystallinity indices for the two major clay
minerals for each core sample by geologic age . 46
6 D-spacing response of the basal smectite peaks
to various treatments of clay samples from the
Pungo River Formation in Onslow Bay 47
7 Peak intensity data based on x-ray diffraction
studies of c1inopti1o1ite 56
8 Model for the deposition of an idealized Miocene
lithologic cycle in response to glaciation and
déglaciation on the S. E. United States conti-
nental margin 63
LIST OF PLATES
Plate Page
1 Location map of the southeastern North
Carolina coastal plain and continental
shelf including Onslow Bay 2
2a Photomicrograph of monocrystalline and
polycrystal1ine quartz 36
2b Photomicrograph of orthoclase feldspar .... 36
3 a SEM photograph of a dolomite rhomb 40
3b Photomicrograph of pelletai phosphate and
intraclastic phosphate 40
4 a Photomicrograph of c1inoptilo1ite laths. ... 43
4 b SEM photograph of c1inopti1o1ite crystals . . 43
5 Photomicrograph of iron coating on quartz
grain 71
INTRODUCTION
The Miocene of the southeastern United States is
characterized by high concentrations of a whole series of
anomalous authigenic minerals , including vast concentrations
of phosphate (Riggs, 1980). These minerals are found in two
contemporaneous units in the southeast: the Hawthorn
Formationof Florida, Georgia, and South Carolina, and the
Fungo River Formation of North Carolina.
The sedimentary units of these formations consist of
complex and interbedded sequences of phosphatic sands, silts,
clays, limestones, and dolomites (Weaver and Beck, 1977;
Scarborough 1981; Riggs and others, 1982a). The clays
include abundant pa1ygorskite, montmori11onite, and sepiolite
in the Hawthorn Formation (Heron and Johnson, 1966; Weaver
and Beck, 1977) and smectite and illite in the Fungo River
Formation of North Carolina (Rooney and Kerr, 1964).
The Miocene phosphatic formations in the southeastern
United States formed in response to oceanographic events of
global extent (Riggs, 1984). Riggs believes that these
highly cyclical deposits with regional patterns of
terrigenous, phosphate, and carbonate deposition were
primarily responses to the interaction of glacial eustatic
sea-level flucuations, climatic changes, and Gulf Stream
dynamic s.
Regional Setting
Onslow Bay (Fíate 1) is an arcuate bay situated on the
2
Plate 1. Location map of the southeastern North Carolina
coastal plain and continental shelf including
Onslow Bay. This map is based upon ERTS NASA/
USDA SAT-L 1973, meter band .8 - 1.1.
78°
CAPE
NATTERAS
; CAPE LOOKOUT
ONSLOV^.'BAY
O STUDY
AREA
CAPE FEAR í.
FRYING PAN kilometers
SHOALS
4
southeas tern Atlantic continental shelf. It i s bordered by
Bogue Banks and Cape Lookout to the north. by the barrier
islands along the outer edge of the North Carolina coastal
plain to the west, by Cape Fear and Frying Pan Shoals to the
south. The eastern boundary is the shelf edge, which occurs
at a depth of approximately 50 meters. Water depths in
Onslow Bay average 20 to 30 meters and grade from 6 meters at
the base of the lower forebeach to about 50 meters at the
shelf edge. The study area is the zone within Onslow Bay
where the Pungo River Formation crops out; this area extends
from the northeastern portion of the bay, southwestward into
the Frying Pan area in southern Onslow Bay and encompasses
2
approximately 9800 km .
Previous Work
Numerous studies of the Pungo River Formation have been
conducted since it was first described by Brown (1958) and
named by Kimrey (1964; 1965). The most important studies
include those of Gibson (1967), Miller (1971; 1982), Brown
and others (1972), Scarborough (1981), Katrosh and Snyder
(1982), Riggs and others (1982a), Scarborough and others
(1982), and Snyder and others (1982a). Pilkey and others
(1967) first described phosphatic sands in the Holocene
sediments of Onslow Bay. Meisberger (1979) described Miocene
phosphatic sands in vibracores taken immediately offshoreof
5
Bogue Banks and Steele (1980) described Miocene phosphatic
sands in auger samples drilled on Bogue banks. Subsequent
studies of the Pungo River Formation in Onslow Bay include
Lewis (1981), Lewis and others (1982), Blackwelder and others
(1982), Snyder, S. W. P. (1982), Snyder S. W. P., and others
(1982), Riggs and others (1982b, in press), and Waters
( 1983 ) .
Clay mineralogy of the Pungo River Formation was first
described by Rooney (1965) in Aurora, NC. He found
montmori11onite and a glauconite illite to be the dominant
clay minerals. The presence of a zeolite, c 1 inopti1o1ite,
led to the suggestion that there were volcanic associations
present at the time of Pungo River Formation deposition
(Rooney and Kerr, 1964; 1967). Potluri (1966) found
glauconite present as silt-sized grains in phosphate pellets
from the Pungo River Formation in Beaufort County. He
related the presence of glauconite and pyrite formation in
phosphate pellets to reducing conditions in the environment
of deposition. Miller (1971) listed mixed-layer
montmori11onite-i11ite and 1 M illite as the predominant
clays along with trace amounts of chlorite in the Pungo River
Formation of the North Carolina coastal plain. He noted that
c1inopti1o1ite is more abundant in phosphate-rich beds than
in clay-rich beds. Meisberger (1979) found glauconite
present and in greater abundance than other material within
the Miocene phosphorite pellets in northeastern Onslow Bay.
Siedlicki (1983) reported smectite and halloysite in the silt
6
and clay fraction of the Pungo River Formation in Aurora.
Objectives
The clay mineral studies mentioned in the preceding
section provide minimal quantitative information concerning
the types of clay in the Pungo River Formation. Of the
studies mentioned, only Rooney (1965) presents a complete
breakdown of clay type with some diagenetic changes.
Detailed studies of the clay mineralogy of Miocene sediments
in Onslow Bay have not been done.
Clay mineral studies can provide insight on 1) recent
and ancient climatic conditions (Biscaye, 1965; Griffin and
others, 1968; Grim, 1968; Chamley, 1979; Kennet, 1982); 2)
environment of deposition (Grim, 1968; Keller, 1970; Carroll,
1970a; Wilson and Pitman, 1977; Weaver and Beck, 1977); and
3) diagenesis (Keller, 1964; Lucas and Ataman, 1968; Grim,
1968; Carroll, 1970b; Reynolds, 1970; Drever, 1971; Gibbs,
1977; Patón, 1978).
The purpose of this study is to determine the clay
mineralogy of the Pungo River Formation in Onslow Bay. More
specifically, the objectives are:
1) to identify the major and minor clay minerals;
2) to determine the lateral and vertical distribution of
the clay minerals in the Miocene sediments;
7
34))toto eclianytesrtfrparbliacettsphalaeuotchliigmeanitcic/dcioangeion; and dniteiotincsaanltedration of thedepositional
environment at the time of sediment formation.
8
GEOLOGIC SETTING
Structure
Onslow Bay is situated on the northern flank of the
Carolina Platform (Snyder, S. W. P., 1982). The platform is
a major first-order, large-scale feature consisting of pre-
Jurassic continental crust that has affected sedimentation
throughout the Cretaceous and Tertiary in this region
(Snyder, S. W. P., 1982). Snyder described various smaller
scale structures which occur on the platform and in the
Onslow Bay area (Fig. 1) and have controlled Neogene
sedimentation, including the following:
1) An Oligocène deltaic depositional series of
prograding clinoforms occurs in western Onslow Bay and the
adjacent coastal plain (Lawrence, 1975; Meisberger, 1979;
Lewis and others, 1 982).
2) The White Oak Lineament, a north to south trending
monoclinal erosional scarp in northern and central Onslow
Bay. The scarp might have been initially associated with a
tensional fault system in the Carolina Platform (Snyder,
S.W.P., 1982), however, recent seismic evidence suggests that
it is entirely an erosional feature. Snyder believes that
the scarp was cut by the Gulf Stream.
3) The Cape Lookout High lies north of Onslow Bay.
This second-order topographic high, trending almost east to
west, separates the adjacent Aurora and Northeastern Onslow
Bay embayments (Scarborough, 1981; Snyder, S.W.P., 1 982).
Figure 1 - Location map of structural and topographie features in the Onslow
Bay area (From Snyder, S.W.P., 1982).
10
4) A series of flexure basins occur near Frying Pan
Shoals. Snyder (S.W.P.,1982) believes that they may
represent the surficial expression of differential subsidence
in the crystalline basement.
5) The Mid-Carolina Platform High is a broad structural
feature extending from Cape Romain, South Carolina, to
central Onslow Bay, North Carolina. It is analagous to the
Cape Fear Arch and is now Interpreted to be the shallowest
portion of continental crust on top of the Carolina Platform
(Snyder, S. W. P., 1982).
Stratigraphy
The lowermost units identified in the Onslow Bay
sedimentary sequences are moldic biomicrites with interbedded
calcarenite sand and grayish green, slightly clayey,
carbonate rich, quartz sands. These sands are tentatively
assigned to the Oligocène Belgrade Formation and the lower
Miocene Silverdale Formation, respectively (Baum, and others,
1979; Riggs and others, 1982b, in press). These units are
unconformably overlain by the Miocene Pungo River Formation.
Three depositional sequences, separated by
unconformities and consisting of at least eighteen
depositional units each composed of interbedded lithofacies,
have been identified in the Pungo River Formation of Onslow
Bay using high resolution seismic profiling (Snyder, S. W.
P., 1982) (Figs. 2 and 3). The three depositional sequences
form a broad northeast to southwest outcrop belt of the Pungo
GEOŒRONOMETRIC ISMCNA.YLE.
Figure 2. Miocene seismic units of Onslow Bay and their lithology (Lewis, 1981; Riggs and others, 1982b
Snyder, S. W. P., 1982). Shaded areas designate sampled units.
12
Figure 3. Location map showing 1) the outcrop belt of the Fungo River
Formation across Onslow Bay; 2) the 3 depositional sequences
of the Fungo River Formation defined by seismic stratigraphy
and biostratigraphy; 3) 15 of the 18+ depositional units
defined by seismic stratigraphy; and 4) the location of vibra-
cores used in this study. The seismic sequences and units are
from Snyder (S. W. F., 1982) and the nomenclature of the units
are for this study only. • = vibracore hole.
13
River Formation across Onslow Bay. The sequences, deposited
along the eastern flank and around the nose of the Mid-
Carolinian Platform High, dip east and southeast off of the
High (Lewis, 1981; Snyder, S. W. P., 1982; Riggs, 1984).
The depositional sequences, consisting of the
Burdigalian (6 depositional units), the Langhian (4
depositional units), and the Serravallian (5+ depositional
units) were probably formed in response to 1-10 million year
duration third-order sea level cycles (see p. 67) (Snyder, S.
W. P., 1982). Each depositional unit is characterized by
vertical and lateral sediment patterns defined by the
terrigenous, phosphatic, and calcareous components, and
deposited in response to the transgressive portion of fourth-
order sea-level cycles of relatively short (< 1 million
years) duration (Riggs, 1984). The cycles also have a
regressive stage which is characterized by non-deposition ,
erosiona! scouring and channeling, and diagenetic alteration
(Riggs , 1 984 ).
The Pungo River Formation in Onslow Bay is unconformably
overlain by 1) various Pliocene and Pleistocene carbonate
sequences and 2) thin and variable thicknesses of Holocene
sands .
14
PROCEDURES
Samp ling
Samples were obtained from vibracores taken in Onslow Bay
in May and October of 1980 from the R/V Eastward (cruise (/E-
3-80) and the R/V Endeavor (cruise #EN-057), respectively,
under the direction of Dr. S. R. Riggs. Lewis (1981)
described the acquisition and subsequent processing of the
cores, as well as preparing core descriptions. Core
locations within the study area are shown in Figure 3. The
vibracores and samples used in this study are listed in Table
1 .
The original purpose of the study was to describe the
mineralogy and texture of the terrigenous component of the
Pungo River Formation. Preliminary examination of Lewis'
data, the vibracores, and whole rock analyses by x-ray
diffraction showed quartz to be the primary terrigenous
mineral. Since terrigenous clays were not considered at that
time, quartz content in Lewis' lithofacies formed the basis
for sample selection. An arbitrary value of >20% quartz was
used to select units for study.
Riggs and others (1982b) developed an economic
classification of the sediment units in the Frying Pan and
northeast Onslow Bay phosphate districts (Fig. 3).
Subsequently, (Snyder, S. W. P., 1982) produced a detailed
seismic-stratigraphic classification for the entire Miocene
section in Onslow Bay (Fig. 2). This latter work indicated
gaps where individual units had been either sparsely sampled
15
UNIT CORE SAMPLE No. DEPTH BELOW
SEDIMENT
SURFACE
(meters)
S-5 1 1 5.00-5.25
S-2 53 1 1.25-1.50
S-2 53 2 3.75-4.00
S-2 53 3 5.25-5.50
S-2 60 1 5.50-5.75
S-1 2 1 4.50-4.75
S-1 4 1 5.50-5.75
S-1 6 1 0.50-0.75
S-1 6 2 3.00-3.25
S-1 6 3 7.25-7.50
S-1 42 1 2.50-2.75
L-2 34 1 2.00-2.25
L-2 52 1 3.50-3.75
L-1 35 1 3.75-4.00
L-1 44 1 1.75-2.00
L-1 44 2 3.00-3.25
L-1 44 3 5.50-5.75
L-1 51 1 4.00-4.25
B-6 15 1* 1.50-1.75
B-6 45 1 1.75-2.00
B-6 45 2 3.50-3.75
B-6 45 3 5.00-5.25
B-6 62 1* 3.50-3.75
B-6 62 2 4.25-4.50
B-6 62 3* 5.00-5.25
B-6 66 1 3.00-3.25
B-6 67 1 3.50-3.75
B-6 67 2* 5.00-5.25
B-6 67 3* 7.00-7.25
B-6 70 1* 2.00-2.25
B-5 48 1 4.00-4.25
B-5 57 1 4.75-5.00
B-2 27 1* 1.50-1.75
B-2 27 2* 3.00-3.25
B-2 27 3* 5.00-5.25
B-2 28 1* 2.00-2.25
B-2 47 1 5.00-5.25
B-2 63 1 2.25-2.50
B-2 97 1* 3.25-3.50
B-1 20 1 1.00-1.25
B-1 20 2 3.50-3.75
B-1 20 3 5.50-5.75
B-1 23 1 2.00-2.25
B-1 29 1 2.75-3.00
B-1 14 1 4.75-5.00
B-1 22 1 4.75-5.00
B-1 30 1 1.00-1.25
B-1 30 2 1.75-2.00
B-1 30 3 2.50-2.75
B-1 30 4 5.00-5.25
Table 1. Vibracores and the sediment samples used in
this study along with their depth below the
sediment surface. *= analyzed for clay min-
éralogy only.
16
or not sampled at all for the present study, and caused some
units to be oversampled. When Snyder's work was completed,
the largest portion of the laboratory work had been finished
and time limitations precluded examining new samples from the
gaps in the same detail as the previously sampled units.
Laboratory Analyses
The general laboratory procedures are outlined in Figure
4. Samples were split using the quartering method (Carver,
1971). Separate splits were made for each sieve and pipette
analysis. According to Folk (1980), the two analyses can be
conducted in this manner if the mud content is relatively
high and the sample is thoroughly mixed before splitting. He
also said that one must assume that both splits have the same
proportion of constituents.
Each split to be sieved or pipetted for grain size
analysis was dispersed (Folk, 1980) using Calgon and placed
in a shaker for 30 minutes. The dispersed sample was wet
sieved in a U.S. Standard ASTM 8", 4 phi (0) (0.0625mm) sieve
to separate the coarser than 4 phi fraction from the finer
than 4 phi fraction.
Sieve An a 1y sis. The coarse fraction was oven dryed at
60° C overnight then sieved through a nest of 0.5 phi
intervals of U. S. Standard ASTM 8" sieves using a Tyler
Rotap Sieve Shaker. Each size fraction was weighed on a
Mettler HIOT Balance. Individual and cumulative percentages
(Appendix A) were calculated for each size interval using the
Unfractionated 17
100 gr. sample
Quartered
sample
I
5 gr. 70 gr. 15 to 30 gr.
for thin for for
section sieve pipette
Wash in 40 sieve Wash in 40 sieve
Coarser than 40 Finer than 40
Petrographic fraction to be fraction to be
microscope sieved for size pipetted for
examination analysis size analysis
to determine I
mineralogy and Binocular study Pp etrogi raphic
texture to determine microscope
shape,roundness, examination
sphericity, and
mineralogy Scanning electron
I microscope
Cathode lumiinescence Scanning electron examination
examination of microscope of selected samples
selected samples examination
of selected samples X-ray study of
the finer than 80
fraction
J
Compilation and
analysis of data
Figure 4. Flowchart of procedures used to accomplish the lab-
oratory analysis.
18
following formulas (Folk, 1980):
Cumulative weight
(1) Cumulative percent = x 100%
Total sample weight
Individual weight
(2) Individual percent = x 100%
Total sample weight
Pipette An a1y sis. The fine fraction from each 15 to 30
gram split was pipetted from 1000 ml cylinders in 1 phi
intervals. Withdrawal times for the pipette analyses and
individual and cumulative percents were computed using the
following formulas (Folk, 1980):
D
(3) T= where: T = time in min
ISOOxAx d^ 9mm) D = depth in in
centimeters
A = density of clay
and quartz de-
pendent on
temperature
d = particle diameter
100(S + F - P)
(4) Cumulative percent =
S + F
where: S = weight of sand on the 4 0 sieve
F = amount of mud in the cylinder
P = quantity of each pipette sample times 50
(5) Individual percent = CW
where: CW is the difference in cumulative weight %
Thin Section An a1y sis. The split samples for thin
sections were placed in 40ml paper cups, mixed with epoxy,
and slabbed for thin sections. The thin sections were
stained with sodium cobaltinitrite and amaranth red to aid in
19
the identification of potassium and plagioclase feldspars,
respectively (Carver, 1971). Preparation and staining
techniques of the thin sections are listed in Appendix B.
Cover slips were not used in order to allow for study by
cathodoluminescence.
Percentages of the minerals present in each thin section
are based on a 300 grain point count using the line method
(Carver, 1971) with a 0.5 mm interval on the mechanical
stage. This technique yielded a counting error of 0.7% to 3%
(Folk, 1980).
Sediment characteristics. Color determinations of the
total sediment were based on wetted samples in sunlight
utilizing the color chart by Goddard and others (1975).
Characteristics of the sand and silt grains, including degree
of rounding and sphericity, were based on charts from Scholle
(1979) and Payne (1974). Sphericity of sand and silt sized
grains in thin section were measured along the long and short
axis with a calibrated micrometer ocular scale. In order to
insure randomness, the first 100 grains encountered in the
point count were used to determine average sphericity and
roundne s s.
Clay An a 1y sis. Clay samples were prepared for x-ray
diffraction analysis utilizing a procedure from Carroll
( 1 9 7 0a) (Fig. 5). However, the clay was separated from the
silt by pipette instead of centrifuge. After pipetting, the
samples were centrifuged at 2 500 RPM for 5 minutes to
separate the water and the clay. The water was decanted, and
20
Size separation by pipette
to obtain finer than 80
material
Wash with deionized water
5 times, centrifuge and
dry clay in oven @60°C
Weigh 50mg aliquots
For oriented samples: For non-oriented samples:
add deionized water, mount dry material in holder
pipette wetted material
onto glass slides,and air dry
X-ray
1
Heat to 400°C Glycolation
X-ray
I
Heat to 550°C X-ray
X-ray X-ray
L
Analyze x-ray data
Figure 5. Flowchart of routine treatments to the finer than
8 phi material of all samples.
21
the clay was washed by stirring in deionized water for 5
minutes and recentr i fuging at 2500 RPM for 5 minutes. All
samples were washed five times, then placed in an oven at 60°
C until dry. Deionized water was added to the clay to make a
slurry, which was pipetted onto a glass slide and allowed to
air dry, producing a preferred basal orientation of the clay
particles on the slide. Powdered material of the finer than
8 phi fraction was packed into fiberglass sample holders and
lightly pressed with a spatula to obtain relatively
unoriented mounts. Oriented slides enabled identification
and quantification of the clay groups while unoriented slides
were utilized for more detailed identification of the clay
types (Thorez, 1976).
Ethylene glycol treatments were used to identify
expandable clay groups (Thorez, 1976). Ethylene glycol,
*^2^6®2’ organic compound that will cause some clay,
such as smectite, to expand by adsorbing the compound onto
interlayer surfaces. The procedure, which was routinely done
for all oriented samples, consisted of suspending the slides
over glycol heated to 60° C until they were moist from the
vapor, followed by x-ray analysis. Heat treatments to all
oriented slides consisted of 1) heating to 400° C for one
hour to test for phillipsite, a zeolite, and to collapse
expandable clays; and 2) heating to 550° C for one hour to
test for kaolinite structural collapse.
Thorez (1976) listed two techniques to identify the
smectite species: K and Mg saturations followed by treatment
22
with glycerol. The procedures from each of five samples (52-
1, 44-2, 23-1, 22-1, and 6-3) involved obtaining two aliquots
of finer than 8 phi material. One aliquot (50 mg) was
saturated in a IN solution of K acetate and the other aliquot
(50 mg) was saturated in a IN solution of Mg-acetate. The
saturations were accomplished by: 1) washing the samples
with the ionic compounds; 2) centrifuging to remove excess
fluid; 3) sedimenting the remainder onto glass slides; and 4)
allowing them to air dry. The treated samples were first x-
rayed, then treated with glycerol (g 1ycero1 ation), and x-
rayed again. Glycerol (C^HgO^), an organic compound, was
applied in the same manner as ethylene glycol.
O O
In order to differentiate between 7A chamosite and 7A
kaolinite, a procedure by Abdel-Kader and others (1978) was
used. According to the procedure, 50 mg of clay is 1) washed
twice with 5 ml 1 N lithium chloride (LiCl) solution for 5
minutes; 2) washed once with 4 ml .IN LiCl and allowed to
stand for 2 hours at 50°C; 3) washed with 9 ml of
dimethy1su1foXide (DMSO) for 5 minutes; 4) washed with 90%
DMSO, < 10% water, and < .OIN LiCl and allowed to stand
overnight at 90°C; 5) centrifuged to separate the supernatant
liquid; 6) mounted on glass slides in routine manner
described in the procedures and x-rayed. The procedure
O O
causes the 7A kaolinite peak to shift to 11.2A while the
O
chamosite peak remains at 7A (see p. 49). Three samples (1-1,
6-1, and 30-3) were treated with the procedure.
23
Samples were x-rayed using a General Electric
(Diano)(XRD-6) X-ray Diffractometer with a Model 700
Detector. Routine instrument settings are given in Table 2.
Pulse height analyses were conducted periodically to achieve
and maintain optimum machine performance. Clay mineral
standards from the University of Missouri were analyzed to
insure accurate clay mineral identification and relative
crystallinity of the illite.
Determinations of clay mineral percentages are close
approximations at best (Biscaye, 1965). The method for
calculating clay mineral percentages of montmori11onite,
illite, kaolinite, and chlorite was adapted from Biscaye. I
O
included the calculation of a 12A clay component which is
interpreted to be sepiolite. The calculation used in this
study consisted of: 1) identifying the basal (001) peaks
from the glycolated runs, 2) determining the area under the
peaks, and 3) using these values in the following formula:
100 X basal peak area of mineral
(6) % of clay mineral in sample =
17A + 12A + lOA + 7A
O
whe r e: 1 7 A peak area o f the 17A0 component times 1
1 2A peak area 0 f the 1 2 A0 component times 1
1 0 A peak area o f the 1 OAo component times 4
7 A peak area o f the 7 A component times 2
To evaluate precision of the clay sample preparation
technique, x-ray diffractometer, and data quantifcation,
sixteen replicate analyses were run on two samples. Both
samples were divided into 4 subsamples each. All subsamples
Console
Milliamps 7
Kvp 45
Meter Range High-A
Diffractometer
Radiation CuKct A=1.5418
Filter Ni
-t ^
Slits 1 mr and .2°
Scan rate 1 /30sec; 1 /mi
Detector
Range 250
Time constant 2.5
Amp gain 16
Potentiometer 140 kv
PHS E
L -280;’E -441U
Rate meter 25 seconds
Table 2. Routine instrument settings
for the x-ray analysis con-
ducted on a General Electric
(Diano) XRD-6 Diffractometer
25
were prepared, mounted on glass slides, and glycolated in the
same manner. Each slide was subjected to four runs on the x-
ray goniometer. On the first two runs, a slide was x-rayed
from 2° to 13° (29-). The slide was removed from the sample
holder in the goniometer and replaced again for runs three
and four.
The clay mineral percentages were then calculated for
each x-ray run. Statistical parameters of mean (x) and
standard deviation (s) were calculated for each clay mineral
in each sample. Precision, or the coefficient of variation
(c), was calculated (Till, 1974):
(7) c = 100s
X
A plot of means versus coefficients of variation (Fig. 6)
shows a range in precision error of 3 to 24% with precision
improving as mean clay percent increases.
Crystallinity index is a factor used to express 1) the
degree of mineral crystallinity and 2) the degree of
degradation of the crystal lattice of the clay. It may also
reflect trends of weathering or diagenetic factors present
either during or after deposition (Thorez, 1976).
Crystallinity indicies were determined for all illite and
smectite minerals present in the samples. Crystallinity of
O
the 17A (smectite) component was determined by the
valley/peak ratio method (Biscaye, 1965; Thorez, 1976 (Fig.
O
7a). Crystallinity of the lOA (illite) component was
determined by peak, characteristics such as height and width
26
100 -,
80
M(CPEELx 60RCAENYN)T 40
20
PRECISION ERROR (c)
Figure 6 Plot of coefficient of variation (c= precision error) vs
mean clay percent.
27
Figure 7a. Method used by Biscaye (1965) and Thorez (1976)
to determine crystallinity of the basal smectite
peak using the formula, C = V/P. = smectite
crystallinity; V= height of valley from apex to
base line; P= height of peak from apex to base
line.
Figure 7b. Method used by Thorez (1976) to determine crys-
tallinity of the basal illite peak using the
formula, Cj = P/W. Cj= illite crystallinity;
P= height of peak from apex to base line; W=
width of peak at 1/2 peak height. Diffracto-
gram is a well crystallized illite standard where
Cj = 10. Crystallinities of Onslow Bay illites
are compared to the standard where 'O' is most
poorly crystallized and '10' is most well crys-
tallized.
28
(Fig. 7b).
Cathodoluminescence. A Nuclide Model ELM 2A Luminoscope
was used for cathodoluminescence examinations of ten thin
sections to detect authigenic overgrowths on quartz grains.
Samples were selected (1-1, 2-1, 4-1, 6-1, 6-2, 20-3, 30-2,
44-2, 62-2, and 63-1) which contained many large (4 phi or
coarser) quartz grains which allowed for easier examination.
The thin sections were cleaned with alcohol to remove any
oils that might contaminate the helium atmosphere in the
luminoscope sample chamber.
Scanning Electron Microscopy (S E M ). Scanning electron
microscopic analyses were performed on sand and silt grains
from samples using an ISI-40 instrument. The purpose of this
analysis was to detect any crystal terminations on quartz
grains or any cleavage present in feldspars to determine
their relative 'freshness'. Crystal terminations or cleavage
might go unnoticed with lower magnification of optical
microscopes.
Approximately 30 milligrams of material from the sieve
and pipette analysis of each sample were combined in a test
tube with a 10% HCL solution, centrifuged at 2 500 RPM for 5
minutes to separate the supernatant, washed twice with
deionized water, and recentrifuged after each washing. After
each washing the washed samples were dried, mounted on SEM
stubs, and sputter coated with go Id/palladium.
Statistics. The statistical parameters used for the
textural analysis included: 1) graphic mean phi size; 2)
29
inclusive graphic standard deviation (sorting); 3) inclusive
graphic skewness and kurtosis; and 4) mode (Folk, 1980).
Values obtained from percentiles in cumulative probability
curves (Appendix C) were used in statistical parameter
formulas (Appendix D). The mode was determined using the
graphic procedure of Folk (1980) which is also described in
Appendix D. Maturity was determined by: 1) using the clay
matrix and sorting values from the petrographic study; 2)
inserting those values into the flow chart (Appendix E); and
3) assigning a classification to the sample of immature,
submature, mature, or supermature.
30
RESULTS
Textural Analysis
Textural analyses of the total, unfractionated samples
were performed to characterize the sediment with respect to
sand, silt, and clay components and to determine any inter-
relationship of the clay and non-clay components. Textural
parameters of the samples (Appendix F) are summarized in
Table 3, while sand, silt, and clay concentrations (Appendix
G) are summarized in Figure 8. Textural parameters and sand-
silt-clay concentrations show the Burdigalian and
Serravallian depositional sequences have similar grain size
characteristics and both sequences are different from the
Langhian.
Sediments in the Burdigalian, Langhian, and Serravallian
sequences are poorly sorted with mean phi sizes in the fine
sand to coarse silt ranges. Twenty-six out of 39 samples are
bimodal or trimodal which may be indicative of reworking,
multiple sediment sources, or sea-level fluctuations.
Studies on shelf sediments have shown that relict sediments
may be in disequilibrium with processes currently acting on
them, particularly during transgressive/regressive sea-level
fluctuations (Emery 1968; Swift and others, 1971; Reineck and
Singh, 1973). Thus, the modality of the sediments may be the
combined results of 4th-order sea-level cycles of the Rungo
River Formation (Riggs, 1984) and the multiplicity of origins
of terrigenous, authigenic, and biogenic components of the
sediment s
N.A. Terr. Sand Silt Clay Mean Size Sorting Skewness Kurtosis
(%) (%) (%) (%) (0)
Serravallian 11 58 64 24 12 3.5 vf sand 4.1 X poor 1.4 sf skewed 2.2 v leptokurtic
Langhian 7 43 45 39 16 4.8 c silt 4.2 X poor .20 f skewed 1.5 leptokurtic
Burdigalian 21 43 62 27 11 3.9 vf sand 3.5 V poor .41 sf skewed 1.7 v leptokurtic
Table 3. Summary of textural data for the 3 depositional sequences in the Pungo River Formation, Onslow
Bay. Terrigenous percentages are taken from point counts of 300 points in the petrographic
analysis. All other percentages were derived from seive and pipette analysis. N.A. = number
of samples analyzed; Terr = terrigenous.
32
SAND
2S:I1LRTatio
Figure 8. Ternary diagram summarizing sand-silt-clay percentages
for the Burdigalian (B), Langhian (L), and Serravallian
(S) depositional sequences. Classification is based on
Folk (1980).
33
The dispersion technique used to break down the clay
fractions may be a problem with respect to the textural
ion of the samples. The technique uses Calgon
to disperse the finer than 8 0 sediment size fraction (Folk,
1980). Clay minerals (e.g. kaolinite) in the finer than 8 0
size fraction can flocculate upon entering marine waters and
settle out with silts, as demonstrated by Gibbs (1977).
Filter feeders may also aggregate fine and deposit
them as larger (coarser than 8 0) fecal pellets (Pryor, 1975;
Potter and others, 1980). Consequently, disaggregation
procedures using Calgon would tend to cause the grain size
distribution to be skewed to the finer side, producing a
distortion from the grain sizes actually deposited. The fine
to strongly fine skewness of the samples (Table 3; Appendix
F) might reflect this laboratory disaggregation.
34
Petrographic Analysis
Thin sections of the Pungo River sediments of Onslow Bay
were examined in order to determine the types and
distribution of terrigenous minerals to supplement the x-ray
analysis. Percentages of minerals present in the samples are
shown in Appendix H. Grain size and roundness values for the
minerals are shown in Table 4. Matrix material, consisting
of quartz, carbonate minerals, and clays, is ubiquitous in
all samples. Quartz is the most abundant terrigenous mineral
in the sand and silt fraction of all samples and is
subdivided into monocrysta 11ine and po1ycrysta 11ine types.
Potassium and plagioclase feldspars, muscovite mica, and
zircon are present as accessory minerals. Small amounts of
glauconite, chert, and opaque minerals are also present in
the Pungo River Formation sediments.
Percentages of terrigenous component in the sand and silt
size range are generally higher in northern Onslow Bay
samples than in central and southern samples. Carbonate
materials are present in all units, with calcium carbonate
shell being the dominant form in southern Onslow Bay samples
and dolomite rhombs in the northern Onslow Bay samples (T.
L. Stewart, pers. comm., 1984). Phosphate is present in most
samples, having its highest concentration in the southern
Onslow Bay samples.
Monocrystalline quartz. This category comprises 95% to
100% of the quartz in the Pungo River Formation sediments
(Plate 2a). Grain surfaces are generally smooth with minor
Distribution
in total Size Roundness Sphericity
sediment (%) Range
Moderate
Monocrystalline quartz 10 - 79 o oo i (47-1) - 0.80mm (4-1) Subangular - subround
Polycrystalline quartz T - 1 0.lOmm (20-3) - 2.30mm (4-1) Subround - round High
Chert 0-2 0.02mm (30-1) - 0.90mm (2-1) Subround Moderate
Potassium feldspar 0-6 0.05mm (6-3) - 0.65mm (6-1) Subround Moderate
Twinned 0-2 0.01mm (14-1) 0.14mm (6-1) Subround Moderatefeldspar -
Untwinned feldspar 0-3 0.01mm (14-1) - 0.25mm (20-3) Subround Moderate
- Low
Muscovite mica 0-2 0.05mm (4-1) - 0.25mm (67-1)
Zircon 0 T 0.06mm (6-2) - 0.13mm (30-2) Subround Moderate-
-
Shell 0 - 37 0.07mm (23-1) - 4.00mm (67-1)
-
-
0 13 0.07mm (20-1) --Shell fragments - 3.00mm (67-1)
0.03mm (1-1) 0.05mm (1-1)
-
-
-
Dolomite rhombs 0 - 8
Sparry calcite 0 - 6 0.01mm (30-1)
- 0.70mm (60-1) --
Pelletai phosphate 0.10mm (23-1)
- 2.70mm (4-1) Round High
Skeletal phosphate T - 34 0.14mm (22-1)
- 0.50mm (4-1) Low
-
Intraclastic phosphate 0.11mm (30-4) 1.20mm (20-3) Subangular - subround
Moderate
Glauconite 0-2 0.03mm (20-1) - 0.12mm (30-1) Subround - round High
- Moderate
Opaque grains T 0.04mm (30-2) 0.15mm (45-1) Angular - subround
Table A. Summary characteristics of mineral grain types found in the thin section study. Sample numbers
are in parentheses. The data is based on 300 grain point and comparison with Payne (1974) and
Scholle (1979). T= trace or <1%.
LO
Ln
Plate 2a. Photomicrograph of moncrystalline quartz (A) and
polycrystalline quartz (B) in sample 20-3. (cross-
ed niçois, 65x)
Plate 2b. Photomicrograph of orthoclase feldspar (in yellow)
in sample 1-1. White grains are quartz, (plane
light, 65x)
37
mm
0.15
mm
38
pitting. Extinction of the monocrysta11ine quartz ranges
from 35% undulatory (65% straight extinction) in sample 35-1
to 97% undulatory (3% straight extinction) in sample 45-2.
Inclusions consist of rods (apatite?) and needles (rutile?)
present in less than 1% of the grains. Vacuoles are present
in most grains. Monocrysta 11ine quartz in the Pungo River
Formation is classified as "plutonic" or "common", according
to Folk's (1980) classification, suggesting a probable
igneous source. Cathodoluminescence study revealed no
overgrowths on the quartz grain and the SEM study revealed no
crystal terminations.
Polycrystalline quartz. This category comprises a small
portion (<1%) of the quartz in the Pungo River Formation
sediments. The individual crystals within the whole grain
are lenticular in shape (Plate 2a). The po1ycrysta 11ine
grains fit the "stretched metamorphic" category of Folk's
(1980) classification which indicates they might have
undergone shear or strain without recrysta11ization.
Feldspars. Feldspars are second in abundance in the
terrigenous sand and silt fraction. Three types of feldspars
occur in the Pungo River Formation sediments: 1) potassium
feldspars: 2) untwinned feldspars, and 3) twinned
plagioclase feldspars.
Potassium feldspars, represented by orthoclase and
microcline, are recognized in thin section (Plate 2b) by
their cleavage and yellow stain resulting from treatment with
sodium CObaltinitrite. Grains having polysynthetic twinning
39
in 2 directions at right angles (Kerr, 1959), were classified
as microcline. Due to the low amount present in the samples
(<1%), the microcline is included with potassium feldspars in
Appendix H.
Untwinned plagioclase feldspars are recognized by their
cleavage, positive (+) biaxial figures, and the pink stain
resulting from amaranth red. I was not able to determine
plagioclase feldspar mineral(s) that comprise this category,
but the stain will not work for pure albite. However, the
stain will work on more calcic varieties (Carver, 1971).
Pink stained, fine silt-sized grains may once have been part
of larger twinned grains that have since been weathered,
leaving individual grains with uniform extinction (Van der
Plas, 1 97 5 ).
Twinned feldspars, other than microcline, are interpreted
to be plagioclase. Albite and oligoclase comprise this
category as determined by the Michel-Levy method for optical
determination (Kerr, 1959).
Carbonates. Four types of carbonate materials occur in
the Pungo River Formation samples including: 1) whole
shells; 2) shell fragments; 3) dolomite rhombs; and 4) sparry
calcite. Whole shells, fragments, and rhombs (Plate 3a) are
pitted, indicating possible solution activity. Dolomite
rhombs show zonation in plane light which might be due to
iron content (Kerr, 1959). Sparry calcite occurs as void
filling material. Authigenic pyrite and sparry calcite coat
and fill the micro-shell material. The pyrite occurs as thin
40
Plate 3a. SEM photograph of a dolomite rhomb in sample 6-1. The
pitted nature of the rhomb surfaces suggest solution
activity or etching.
Plate 3b. Photomicrograph of pelletai phosphate (A) and intraclastic
phosphate (B) grains in sample 22-1. White angular grains
are quartz. (plane light, 65x)
41
mm
42
covering on the surfaces of shell fragments, whereas calcite
occurs as anhedral particles attached to inner surface of
foraminifera 1 tests. In sample 60-1, the calcite infilling
of tests is so complete as to be almost indistinguishable
from sparry calcite.
Phosphate. Phosphate is present in most Pungo River
Formation samples. Three varieties of phosphate grains were
observed in thin section: 1) pelletai phosphate, round to
oval-shaped grains which often have rims, are most common
(Plate 3b); 2) skeletal material consisting primarily of
bone, teeth, and shell fragments; and 3) intraclastic
phosphate, are irregular shaped grains with quartz and
feldspar inclusions (Plate 3b). More detailed information on
phosphate types can be found in Riggs (1979) and Scarborough
( 1980) .
Clinoptilollt e. Lath-shaped crystals were first
observed in small amounts in the silt fraction. The laths
are not easily observed in whole sample thin sections since
they are relatively small (<.04mm) and are probably masked by
clay- and silt-sized material and because of their very low
birefringence. The crystals are transparent in plane light
(Plate 4a) with an index of refraction in blue light of
approximately 1.490. Under crossed niçois, the crystals are
only slightly anisotropic. Cleavage is perfect in one
direction (Plate 4b). Rooney and Kerr (1964) described
c1inoptilo1ite in the Pungo River Formation at Aurora. These
lath-shaped grains are interpreted to be c1inopti1o1ite on
43
Plate 4a. Photomicrograph of clinoptilolite laths in sample 6-1. The
laths are similar to those described by Rooney and Kerr (1964)
for the Pungo River Formation in the Aurora area. (plane
light, 40x)
Plate 4b. SEM photograph of the same crystals in Plate 4a above.
44
45-
the basis of their optical (Deer and others,
1 963 ) .
Matrix. The ubiquitous very fine silt- and clay- sized
material consists of quartz, feldspars, dolomite, calcite,
and clay minerals. The remainder of this section will
consider the clay mineral fraction of the matrix material.
Clay Mineral Analysis
Clay mineral percentages (Table 5) were determined for
all 39 samples selected for mineralogical and textural study.
An additional eleven samples were selected from the Frying
Pan Area to give a more complete picture of the clay
mineralogy. Four principal clay mineral types, smectite,
illite, chamosite, and sepiolite, as well as a zeolite,
c 1 inopti1o1ite , were found in the Pungo River Formation
samples. Average clay mineral percentages of the 3
depositional sequences indicate that Burdigalian and
Serravallian clay suites are generally similar to each other
and different from the Langhian.
O O
Smectite. Smectite is defined as 14A to 16A expandidle
phy 11osi1icate in which the basal (001) peak shifts to a
higher d-spacing (17A) after treatment with ethylene glycol
(glycolation) (Thorez, 1976). All samples were treated with
ethylene glycol as a test for smectite.
Responses of the basal (001) smectite peak to the
treatments are shown in Table 6. Untreated samples have
46
UNIT CORE SAMPLE CLAY Smec Ill Cham Sep Clin 001/002
z Cl % Cl % % for
illite
S-5 1 1 14 27 .53 63 7 10 _ P 5
S-2 53 1 2 50 ;60 45 1 4 - P 8
S-2 53 2 11 61 .46 38 3 - - P 12
S-2 53 3 17 66 ? .57 33 1 - - P 8
S-2 60 1 40 58 .61 41 1 - - - 8
S-1 2 1 14 57 .83 29 4 13 - P 4
S-1 4 1 10 59 .69 37 5 4 - P 5
S-1 6 1 12 71 .48 25 2 4 - P 5
S-1 6 2 5 56 .63 41 3 3 - P 3
s-1 6 3 11 70 .58 29 5 1 - P 4
S-1 42 1 5 59 .51 40 7 1 - P 6
•
avg. 7+ 11+ 12 58 .59 38 4 4 - P 6
SERR VALLIAN L-2 34 1 23 45 .98 41 1 - 14 - 25L-2 52 1 16 4 .42 89 3 - 7 - 20L-1 35 1 7 14 .55 86 4 - - - 9L-1 44 1 16 17 .47 81 3 - 2 - 8L-1 44 2 7 16 .41 79 7 - 5 - 24L-1 44 3 32 27 .78 66 3 - 7 - 14L-1 51 1 8 65 .73 26 1 - 9 - 5avg. 5+ 7+ 16 24 .62 70 3 - 6 - 15LANGHIAN B-6 15 1 - - - 100 1 « - - 5S-6 45 1 5 30 .50 64 2 - 6 - 21B-6 45 2 1 83 .57 16 1 - 1 - 4B-6 45 3 6 48 .47 52 2 - - - 17B-6 62 1 - 67 .15 9 2 24 - - 2B-6 62 2 1 51 .72 23 2 26 - P 6B-6 62 3 - 64 .74 33 2 - 3 - 15B-6 66 1 25 61 . 79 26 2 - 13 P 10B-6 67 1 - 12 .55 59 3 29 - - 12B-6 67 2 13 56 .60 41 2 - 3 P 14B-6 67 3 - - - 54 3 6 40. P 7B-6 70 1 - 16 .38 84 4 - - - 5B-5 57 1 7 62 .45 38 1 - - P 8B-3 48 1 2 68 .62 24 1 - 8 P 8B-2 27 1 - 57 .69 39 2 4 - P 9BURDIGALIAN B-2 27 2 - 60 .68 32 2 8 - - 7B-2 27 3 - 64 .62 29 2 7 - - 6B-2 28 1 - 41 .68 59 2 - - P 2B-2 47 1 41 - - 100 2 - - - 8B-2 63 1 9 46 .66 52 3 2 - P 5B-2 97 1 - 59 .15 38 1 - 3 - 8
B-1 20 1 12 64 .64 18 2 - 18 P 3
B-1 20 2 7 57 .81 40 2 - 3 - 12
B-1 20 3 6 57 .58 39 2 - 4 - 8
B-1 23 1 13 60 .76 34 1 - 6 - 3
B-1 29 1 11 53 .42 42 2 5 - - 6
B-1 14 1 5 70 .71 28 2 1 - P 11
B-1 22 1 6 25 .54 70 2 - 5 - 36
B-1 30 1 15 34 .45 59 2 7 - - 8
B-1 30 2 4 56 .51 33 3 11 - - 4
B-1 30 3 6 46 .61 36 2 18 - - 5
B-1 30 4 14 52 .62 28 4 20 - * 5
avg. 19+ 32+ 11 49 .52 42 2 5 4 P 9
Table 5. Total clay percentages of specific clay minerals and crystal-
linity indices (Cl) for the two major clay minerals. The
table also denotes the presence (P) of clinoptilolite (Clin)
in the samples. Smec= smectite; 111= illite; Cham= chamosite;
Sep= sepiolite.+= total cores and samples analyzed in each unit.
Sample Burdigalian Langhian Serravalliai
Treatment ^ 22-1 23-1 44-2 52-1 6-3
0 O O 0 0
Untreated 14. OA 14. OA 15. OA 15. OA 15. OA
0 0 O O
Ethylene glycol 17. OA 17. OA 17. OA 17. OA 17. OA
o O O O O
Magnesium saturation 18. OA 16. OA 16. OA 15. OA 13. OA
Magnesium saturation/
glycerol 18. OA 17. OA 17.OA 17.OA 18.7A
0 O 0 O 0
Potassium saturation 10. OA 10. OA 10. OA 10. OA 10. OA
0 o 0 o o
Potassium saturation/ 14. OA 13.OA 13.OA 13. OA 13. OA
glycerol
O O 0 O O
400°C heating 10. OA 10. OA 10. OA 10. OA 10. OA
o o o o o
550°C heating 10. OA 10. OA 10. OA 10. OA 10. OA
Table 6. D-spacing response (in angstroms) of the basal (001) smectite peaks to various
treatments of clay samples from the Pungo River Formation in Onslow Bay.
48
O O
peaks with a 14A or 15A d-spacing. Treatment with ethylene
glycol causes an expansion of the peak to 17Â, identifying
the clay mineral as an expanding type (Fig.9). The LiCl-DMSO
procedure of Abdel-Kader and others (1978) expands the peak
0 0
to 18À which collapses, upon air drying, to 14À (Fig. 9).
Magnesium saturation followed by glycero1ation identifies the
clay mineral as a montmori11onite rather than a vermiculite
clay because vermiculite will not expand after this treatment
(Thorez, 1976). According to Harward and others (1969), the
expansion of the peak following Mg-saturation/glycerolation
also rules out beidellite, an aluminum and silica rich
O
smectite, because the beidellite peak remains at 14A. Rooney
(1965) determined the smectite present in the Fungo River
Formation in Aurora to be a high K-montmori1Ionite.
All samples were subjected to heat treatments, which
O
collapsed the smectite basal peak to lOA (Fig. 9). Thorez
(1976) believes that heat treatments may help determine
whether smectite was formed 1) authigenlcally from alteration
of volcanic material, augite, hornblende, feldspars, or
hydrothermal solutions; or 2) transformed from mica due to
0
weathering. Mica-derived smectite will collapse to lOA,
O
while authigenic smectite collapses to 9.5A (Thorez, 1976).
He believes the higher angstrom collapse of the mica-derived
variety is due to the presence of ions in the smectite
layers inherited from the parental mica structure.
Paragenesis of the smectite is also indicated by the K-
acetate and glycerol saturations. Potassium saturated, mica-
Chamosite Illite Smectite
Figure 9. X-ray diffractograms of sample 30-3
showing basal peak responses to listed
routine treatments as well as LiCl-DMSO
treatment.
50
derived smectite collapses to lOA while authigenic smectite
g
would give a 12A spacing (Weaver, 1958). Potassium
saturation followed by glycerolation allows for an expansion
O
of the basal peak up to 14A for mica derived smectite and
riSA for authigenic smectite (Table 6) (Thorez, 1976).
Table 5 contains the crystallinity ratios for smectite in
the Fungo River Formation samples. These data indicate that
smectite is well crystallized (Biscaye, 1965; Thorez, 1976),
with crystallinity values slightly higher in the Langhian and
Serravallian sequences than in the Burdigalian.
O
111ite. Illite is defined as a lOA phyllosilicate whose
basal (001) peak is not affected by glycolation (Gaudette and
others, 1964). LiCl-DMSO saturation (Abdel-Kader and others,
O
1978) produced no change in the lOA peak (Fig. 9). Three
illite species were identified on the basis of their 060
(hkl) peaks, if present, on the diffractogram. Illite
varieties included dioctahedral IM and IMD polymorphs and a
trioctahedra 1 variety, glauconite. Dioctahedral clays
have trivalent ( + 3) charge cations (e.g. A1 Fe ?^)and
1 9
trioctahedra 1 clays have a divalent ( + 2) charge (e.g. Fe ’
I o
Mg ‘^)in the octahedral sites. According to Grim and others
(1951) glauconite fits the trioctahedra 1 classification on
the basis of x-ray analysis, even though it is dioctahedral
on the basis of chemical analysis. Due to the poor quality
of the 060 peaks, no attempt was made to quantify the illite
The ratio of 001 to 002 (001/002) peaks in the same
51
sample is a significant indicator of Fe content in the
octahedral layers (Grim and others 1951; Thorez, 1976)
Ratios greater than three indicate Fe-rich illites and ratios
less than two indicate Mg-rich illites (Thorez, 1976). On
this basis, all but two of the samples are Fe-rich (Table 5)
(Thorez, 1976).
Crystallinities of the illite in the Onslow Bay samples
(Table 5) generally rank low when compared to a crystallinity
scale in which 10 is maximum crystallinity (Fig. 7b). Three
samples are exceptions to this; samples 1-1, 42-1, and 44-2
have high crystallinities (-7). Warshaw and Roy (1961)
interpret well crystallized Fe-rich illite to be celadonite
and poorly crystallized Fe-rich illite to be glauconite.
Chamosite. Two types of chamosite have been described in
the literature. First is a kaolinite-type chamosite having a
O
7A basal (001) peak that does not expand upon glycolation and
collapses upon heating to 550° C. Second is a chlorite-type
0
clay mineral having a 14A basal (001) peak that does not
expand upon glycolation and does not collapse upon heating to
o ®
550 C (Carroll, 1970a). No 14A non-expandab1e peaks were
O
found in the Fungo River Formation samples. A 7A non-
expandable peak was found in 22 samples.
Thorez (1976) said that a poorly crystallized kaolinite
may be difficult to differentiate from a chamosite clay
mineral. The procedure by Abdel-Kader and others (1978)
O 0
causes the 7A kaolinite peak to shift to 11.2A while the
0
chamosite peak remains at 7A (Fig. 9). Three samples (1-1,
52
6-1, and 30-3) were treated with the procedure. The 7À peak
after treatment indicates chamosite, but the overall quality
of diffractograms is poor.
Due to the lack of an available chamosite standard,no
crystallinities were determined. It is possible, however, to
get a relative crystallinity by examining peak symmetry
(Thorez, 1976). A poorly crystallized peak (Fig. 10a) is
assymetrica1, broad, and blunt, while a well crystallized
(Fig. 10b) peak is more symmetrical, narrow, and sharp.
Crystallinity of chamosite in the Fungo River Formation
samples is poor to moderate.
Sepiolite. Sepiolite is a clay mineral whose structure
is similar to that of amphiboles with amphibole-like silica
chains parallel to the mineral fibers (Carroll, 1970a).
"Zeolitic water" (water loosely held in the lattice and lost
at low temperatures) is present in interstices between
amphibole chains. This clay mineral is not affected by
glycolation or heating to approximately 300° C. An
incremental increase in heating to 420° C causes the 12A
O
(110) peak to collapse to approximately lOA (Fig. 11). This
collapse results from driving off 'bound water' (OH2) or
crystalline water within the sepiolite structure (Caillere
and Henin, 1972).
Due to the lack of sepiolite standards, no crysta 11inites
O
were determined. Shape of the 12A peaks are all degraded and
assymetric to the high angstrom side (Fig. 11) indicating a
relatively poor sepiolite ci
I
Figure 10. 7A d-spacing of two samples. (A) shows poorly cry-
tallized assymetrical peak in sample 29-1 and (B)
shows a moderately well crystallized, more symmetrical
peak.
Ui
U)
54
.Clinoptilolite Illite Sepiolite
8.9A lOA 12A 29A
Figure 11. X-ray diffractograms showing heat treatments
to sample 67-3 and the corresponding left-
ward shift of the 12À sepiolite peak towards
the 10Â position.
55
Clinoptilolite. Clinoptilolite is defined as a
potassium- and sodium-rich member of the heulandite
structural group of the zeolites (Hay, 1966). While not a
clay mineral, it did show up in the x-ray analysis of the
O
clay fraction. The relative stability of the 9A 020 peak
throughout the heat treatments (Fig. 11) indicates
clinoptilolite rather than heulandite (Rooney and Kerr,
1964). Due to the lack of an adequate quantifiable procedure,
no percentages were determined for this mineral.
Clinoptilolite is present throughout the Serrava 11ian , not
detectable in the Langhian, and present infrequently in the
Burdigalian sediment units.
X-ray data for clinoptilolite is shown in Table 7.
Onslow Bay samples and a published standard of Chen and
Others (1978) are based on unoriented mounts.
Rooney and Kerr (1964) used oriented mounts for their
analysis of Pungo River Formation samples from Aurora.
Due to lack of data concerning clinoptilolite
crystallinities, no crystallinities were determined for the
mineral in the Onslow Bay samples. However, all samples
containing clinoptilolite have a slightly assymmetric to
symmetric, sharp peak indicating fair to good crystallinity.
D-spacing Peak intensities
(Â) (1) (2) (3)
8.93 100 100 100
7.94 86 70 42
6.81 26 - 22
5.14 20 - 24
4.65 26 - 18
3.97 93 100 98
3.92 53 57 57
3.41 46 - 44
Table 7. Peak intensity data based on x-ray diffraction
studies of clinoptilolite from (1) the Pungo
River Formation in Onslow Bay; (2) Pungo River
Formation in Aurora, N.C. (Rooney and Kerr,
1964); and (3) a published standard (Chen and
others (1978).
57
DISCUSSION
Smectite and illite are the principal clay minerals in
the Fungo River Formation sediments of Onslow Bay and
sepiolite and chamosite are accessory clays. A zeolite,
cIinoptilo1ite , is also present in minor concentrations. X-
ray analysis suggests that smectite and c1inopti1o1ite are
well crystallized, while the illite, chamosite, and sepiolite
are moderate to poorly crystallized.
Rooney (1965) speculated on the paragenetic sequence
that lead to the presence of montmori11on i te, illite, and
c1inopti1o1ite being present in the Fungo River Formation in
the Aurora area (Fig. 12). He believed that some volcanic
glass altered to glauconite and later altered to
montmori11onite. The remaining portion of unaltered glass
produced the zeolite. According to Rooney, the first stage
of this transformation, glass to glauconite, would take place
in an environment of low Eh. As conditions became more
oXidizing, zeo1ite would form from the remaining glass and
glauconite would alter to montmori11onite. The glauconite to
montmorillonite transformation is structurally feasible since
both clays are dioctahedral with trivalent cations in their
octahedral sites. Rooney believes the transformation from
glauconite to montmorillonite would require a loss of K, Na,
and Ca from interlayer positions of the glauconite and
oxidation of divalent Fe. The zeolite transformation might
happen as Si and A1 from decomposing glass combines with the
K, Na , and Ca
Volcanic glass
Decomposition
Al, Si cations Glauconite
Clinoptilolite
Figure 12. Flow chart showing the paragenetic sequence of the clay
zeolite suite in the Fungo River Formation of Aurora ac
cording to Rooney (1965) .
59
A problem with Rooney's hypothesis is that no glass
structures or shards have been found in either the Pungo
River Formation at Aurora (Rooney and Kerr, 1964) or in the
Pungo River Formation sediments of Onslow Bay. However, it
is probable that if the glass was present, it was
subsequently altered or transformed, leaving no direct
evidence of its presence. Another problem with Rooney's
glass-to-g1auconite-to-montmori11onite transformation is the
alteration process itself. If glass is altering to illite in
the high Na, K, and Ca environment that he requires to build
zeolites, what would cause the illite to degrade to a
montmori1Ionite? Bonding between adjacent sheets of illites
is stronger than in smectites because there are more
interlayer cations and less water (Warshaw and Roy, 1961).
Interlayer cations, such as K, hold the layers together with
stronger ionic bonds, whereas interlayer water is bonded by
weaker hydrogen and Van der Waals bonds. Rooney's ideas,
though admittedly speculative, illustrate the problems
associated with interpreting the paragenetic sequence of
clays and their diagenesis in the Pungo River Formation
sediments.
Another approach to understanding the genesis of clay
minerals is to consider the role of regional environment in
clay mineral formation. Biscaye (1965) and Griffin and
others (1968) found that the clay mineral component of Recent
Atlantic Ocean sediments is primarily detrital and reflects
continental weathering environments. The studies have
demonstrated latitudinal trends of clay minerals which formed
on land and were transported to and deposited in the oceans.
The latitudinal trend shows increasing amounts of illite and
chlorite toward higher latitudes and smectite and kaolinite
toward the lower latitudes. Kennet (1982) carried the idea
of continental weathering patterns and clay mineral formation
one step further. If the type of clay in a soil strongly
reflects climatic control, there should be a relationship
between clay mineral distribution in depositional basins to
climatic patterns on adjacent landmasses.
Some clay formation in soils is the result of
decomposing rock-forming minerals (e.g. feldspars, micas,
amphiboles, etc.) and other clays due to chemical weathering
by groundwater. The more water that is flushed through the
pedogenic environment, the more complete the decomposition.
Since rainfall and temperature generally increase with
decreasing latitude, simpler 3 and 2 layer phy11osi1icates
form in low latitude regions. Conversely, drier and colder
climates of higher latitudes tends to favor the formation of
more complex 3 and 4 layer phy11osi1icates.
Patón (1978) cited an example of weathering a
dioctahedral mica in a pedogenic environment. As K ions are
removed by hydrolysis, exfoliation occurs, causing thinner
phy 11osi1icate plates and formation of illite. As the
process continues, water begins to occupy interlayer sites
forming montmori11onite. If the process were to continue
under severe leaching conditions the structure would
breakdown to kaolinite, due to loss of A1 in the octahedral
layer and complete removal of one tetrahedral layer. Patón
believes that the transition from illite to montmori11onite
is mainly superficial, in that alteration is confined to
removal of non-framework cations (i.e. K) while leaving the
phy11osi1icate structure intact. Silicon and A1 , the two
principal cations of the framework structure, maintain the
same ratio of SÍO2/AI2O2 throughout the transition.
According to Grim (1968), the SÍO2/AI2O2 ratio increases as
the transition proceeds from illite to montmori1Ionite. This
results in a decreased charge imbalance allowing K to be
stripped away and water to enter between layers.
Cation deficient water plays a key role in the leaching
process in two ways (Keller, 1964). First, in a semi-arid
environment where evaporation exceeds rainfall, leaching
occurs initially. Then as the water evaporates, cation
availability increases, decomposition is terminated and
montmori11onite is produced. Second, if rainfall exceeds
evaporation and there is good drainage to flush out cations,
alteration continues to kao1inization. In areas where
rainfall exceeds evaporation and drainage is poor,
montmori11onite is produced; initial leaching occurs but
cations cannot be transported out of the system and the
transition is terminated producing montmori11onite as the end
product .
Riggs (1984) proposed a model for deposition of the
phosphorite sediment sequence on the southeastern United
62
States continental margin. The sedimentation model (Table 8)
is a direct response to major climatic events which resulted
in cyclical glaciation and déglaciation and associated sea-
level fluctuations. This idealized cycle model corresponds
to the depositional units of Snyder (S. W. P., 1982) (Fig.
2). In his model, changing pa 1eoc1imates affected the
weathering processes and determined types and volumes of
terrigenous sedimentation from adjacent land areas; these
changing patterns should be reflected in the type of
terrigenous clay minerals formed (Riggs, pers. comm., 1984.
For example. Grim (1968) noted that glacial deposits in North
America have higher concentrations of illite while warmer
climate deposits have higher amounts of montmori1Ionite and
kao1init e.
Chamley (1976) (Fig. 13) proposed a model for clay
mineral formation on land in response to warm and cold
climatic regimes. The subartic to boreal climate on the
Chamley model should equate to the maximum regression stage
of Riggs' cycle model (Table 8). The temperate climate on the
Chamley model should equate to the maximum transgression
stage of the cycle model. Illite and chlorite form in
response to cooler and drier climates, while pedogenic
smectite and kaolinite form in warmer and wetter climates.
Colder climate and lower sea level equates to higher relief
and reduced vegetative cover, allowing faster runoff of
sediment particles and cations (Copeland and others, 1983).
Consequently, clay minerals are more rapidly eroded and
63
(1) Sea level at early- to mid-stage Moderating climate; westward
transgression migration of Gulf Stream;
fine grained terrigenous sed-
iment backfills fluvial chan-
neis and estuaries; interbeds
of phosphate and carbonate;
fine grained terrigenous mud
and sand dominate inside of
•
embayed shelf system.
(2) Sea level at mid- to late-stage Transgression continues; warm-
transgression ing of shelf waters; continued
westward migration of Gulf
Stream; decreasing terrigenous
sedimentation and increasing
phosphate deposition.
(3) Sea level at maximum during Warm climatic conditions; min-
interglacial stage imal terrigenous sedimentation;
sub-tropical marine fauna, local
phosphate pavements and bypass
surfaces; erosion and channels
caused by Gulf Stream current.
(4) Regression with sea level at a Lowering of sea level allowing
minimum during a glacial maximum for eroding, truncating, and
channeling of previously depos-
ited sediments; eastward mi-
gration of Gulf Stream; colder
and arid climatic conditions;
increased terrigenous sedimenta-
tion on shelf ; subaerial or sub-
marine non-depositional ex-
posure.
Table 8. Model for the deposition of an idealized Miocene lithologic
cycle in response to glaciation and déglaciation on the S. E.
United States continental margin (from Riggs, 1984).
64
COASTAL PLAIN PIEDMONT
CONTINENTAL DOTOSTREAM UPSTREAM
SHELFZONEZONE
C, I = Chlorite, Illite = Soil
S, K = Smectite, Kaolinite “ Zone of erosion
Figure 13. A generalized model for continental clay mineral formation
in (A) subarctic to boreal and (B) temperate climatic
regimes (modified from Chamley, 1976). The subarctic to
boreal climatic zone would be characterized by decreased
temperature, rainfall, and vegetation and increased
terrigenous imput to the adjacent shelf. The temperate
climatic zone would be characterized by increased temperature,
rainfall, and vegetation and decreased terrigenous imput
to the adjacent shelf.
65
transported eastward during the initial phase of a glacial
eustatic low sea-level. Later, when the climate warms, these
less weathered deposits are drowned and reworked by shelf
processes. At this time, coastal rivers are drowned forming
estuaries. Erosion decreases and deep soils are favored.
This allows illites and chlorites to alter to smectite and
kaolinite minerals.
Smectite is the dominant clay in the Serravallian
sediments analyzed. According to Chamley's model (1976), a
warm moist climatic condition should have prevailed during
the Serravallian with a corresponding high sea level. Illite
is the predominant clay in the Langhian sediments analyzed.
Consequently, cooler and drier climates should have prevailed
with a correspondingly lower sea level during Langhian
deposition. Clay suites in the Burdigalian sediments
analyzed appear more complex, fluctuating between dominantly
smectite and illite.
A plot of average smectite and illite percentages for
the ten depositional units sampled in this study shows
smectite decreasing and illite increasing toward the top of
each depositional sequence (Eig. 14). A strict interpretation
of the data with respect to Chamley's model conflicts with
the sea-level data of Vail and others (1979). A major
second-order cycle of relative sea level rise (Fig. 15)
occurred from about 30 mya, in the late Oligocène, to about 6
mya, in the late Miocene. This overall transgressive event,
during which the Pungo River Formation was deposited, is
66
SMECTITE ILLITE
0 100% 0 100%
S-5
S-2
S-1
SE L-2L-1LA B-6B-5BURRNDAIGVAHLLIAIANN B-3B-2
B-1
Figure 14. Plot of average smectite and illite
percentages in each of the sampled
Pungo River Formation units. Dark
bars indicate range based on the
precision error in Figure 6.
67
Figure 15. Global cycles of relative sea-level change during the early
to middle Miocene. A= third-order sea-level cycles of Vail
and others (1979); B= fourth-order sea-level cycles of Sny-
der (S. W. P., 1982) and Riggs (1984); and C= present sea-
level.
68
punctuated by smaller scale third-order cycles of
transgression and regression suggesting alternating climatic
conditions superimposed on the larger scale warming trend.
In addition, Snyder (S.W.P., 1982), and Snyder, S.W.P., and
others (1982) Riggs and others (1982b) and Riggs (1984) have
demonstrated that at least 18 still smaller scale, fourth-
order sea-level fluctuations occur superimposed upon the
second- and third- order cycles. An interpretation of the
Vail curves with respect to Chamley's model predicts
increasing abundances of smectite during deposition of the
Pungo River Formation. There are at least two possible
explanations for the apparent discrepancy between the Onslow
Bay data to that of Vail and others ( 1 9 7 9 ) interpreted with
respect to Chamley's model ( 197 6).
First, the illite clay at the tops
of depositional sequences could be glauconite,
which is an authigenic clay formed in marine
environments. Glauconite has been reported in
the clay fraction in the Pungo River Formation
(Rooney, 1965; Meisberger, 1979) as well as in
the sand and silt fraction (Appendix H)
(Potluri, 1966; Meisberger, 1979). Due to
diluent effects of clays in a mixture, the 060
peaks are not adequately discernable and
percentages of glauconite in the samples could
not be determined. Relatively small amounts
of K in the interlayer structure causes
glauconite to have a symmetric peak to the low
angle side of x-ray diffractograms. Asymmetry
of the 10Â peak indicates a degraded condition
which is easily confused with IMd illite
(Carrol, 1970a). Confusion may be further
compounded because glauconite in
unconsolidated sediments not subjected to
pressure does not develop hkl (e.g. 060)
reflections (Carroll 1970a).
Glauconite can form when there is: a)
clay (e.g. smectite) present which can be
69
built into an illitic three layer clay; b) a
local reducing environment exists; and c)
sufficient cations, including trivalent Fe are
present to build the material into an illitic
clay (Burst, 1958). Carroll (1970a) found
that illite formed in reducing conditions does
not develop the characteristic green-colored
glauconite, that develops from a high Fe
smectite which is altered to illite. The
reaction she described proceeds as follows:
(8) Fe smectite + K (Ca, Mg) -«glauconite (IMd)
Smectite from the adjacent landmass could
have been a likely source material for the
illitic glauconite in the Fungo River
Formation samples in Onslow Bay.
Second, the sampling pattern used for
this study did not take into consideration the
cyclic sedimentation in the Fungo River
Formation. Samples high in illite may merely
reflect a point in the section which was
deposited during sea-level regression. The
sampling pattern used in this study may
include the integrated effects of second-
order, third-order, and fourth-order cycles.
However, there is a slight increase in average
smectite percentages from the Burdigalian to
the Serravallian (Table 5). The increase
might indicate a partial correlation of the
data to the Vail curves during third order
cycles.
Chamosite occurs in 18 of the 22 samples in the
Serravallian and in some samples of the Burdigalian.
Chamosite is usually the predominant accessory clay when
smectite dominantes the clay mineral fraction (Table 5).
Chamosite is an Fe-rich phy11osi1icate with a kaolinite type,
O
2 layered, 7A structure. Like glauconite, chamosite requires
a high Fe source, generally reducing conditions, and a
material from which to form. If Chamley's model is correct,
then degraded clay from terrestrial weathering processes may
supply a source material for chamosite.
70
Abundant sources of Fe are available on the marine
continental shelf for formation of chamosite and glauconite.
In non-clay components, Fe occurs 1) as oxide/hydroxide grain
coatings (Plate 5); 2) as dissolved divalent Fe; 3) in
suspension as colloidal particles; 4) as a constituent of
clastic particles (Appendix H); and 5) as chelated organic
complexes (Mehra and Jackson, 1960; James, 1966; Carroll,
1970a; Gibbs, 1977). Iron-stained sands occur over extensive
portions of the shelf south of Cape Hatteras; these sediments
may have originated in subaerial environments of the Piedmont
(Judd and others, 1970; Milliman and others, 1972). Doyle
(1967) found that lack of Fe staining in shelf sediments
suggests an oxygen-poor depositional environment in which the
staining was removed by iron sulfide formation. Iron stained
grains constitute less than 10% of the sediment in all
samples. Iron occurs in average concentrations of 670ppb in
streams and lOppb in seawater (Turekian, 1969; Anikouchine
and Sternberg, 1981). Lower values of dissolved Fe in ocean
water are due to the higher alkaline pH's of sea water than
river water; this causes Fe to precipitate (White and others,
1963) enabling it to be remobilized and concentrated in
authigenic sediments by chemical reactions on the sea floor
( Jame s , 1 9 6 6).
Degraded kaolinite, stripped of some of its A1 and Si
and deposited on the shelf, could serve as the initial clay
material for producing chamosite. James (1966) described a
mixed layer kaolinite-chamosite suggesting such a
71
Plate 5. Photomicrograph of iron coating on quartz grain and
infilling a dissolved inclusion in sample 20-3.
(plane light, 250x)
0.018
mm
73
transformation is possible. Chamosite, which has much more
magnesium than kaolinite, could obtain the Mg required for
the transformation from sea water. Magnesium, the fifth most
abundant element in the ocean has an average concentration of
l,350ppm in sea water (Horne, 1969; Anikouchine and
Sternberg, 1981). Drever (1971) found that, in highly
reducing conditions, divalent Mg from sea water can replace
Fe in exchangible sites in the montmori11onite structure.
Free Fe liberated from this exchange is then available for
transformation of kaolinite to chamosite and smectite to
glauconite under reducing conditions.
Sepiolite occurs most commonly in highly alkaline,
evaporitic environments, where silica and Mg concentrations
are high and A1 is low (Weaver and Beck, 1 97 7 ). Grim ( 1 968)
and Weaver and Beck (1977) believe that sepiolite forms
authigenically in transitional sediment environments such as
lakes, lagoons, bays, and soils, as opposed to more open
marine conditions. Supplies of necessary ions (e.g. Mg and
Si) are derived from upstream hydrolysis which are trapped in
downstream zones and are available for crystallization into
sepiolite.
In contrast, Isfording (1973) found that sepiolite can
form as a direct precipitate in alkaline (pH-8) marine
environments where silica concentrations are high. According
to Isfording, silica leached by subaerial weathering from
phy 11osi1icates during warm, moist climatic conditions is
transported to the shelf by fluvial processes. When proper
pH conditons and silica and Mg concentrations are high
enough, the following reaction occurs:
(9) 2Mg +2 + 3 s^o 2aq + (n+2)H20 = Mg 2 S i 3 Og ( H2 0 ) + 4H+
If more arid conditions lead to sepiolite formation as
suggested by Grim (1968) and Weaver and Beck (1977) other
contemporaneous evapor i te-re1 ated sediments might occur in
association with the sepiolite. Since none have been
documented in the Fungo River Formation, Isfording's
hypothesis for the formation of sepiolite may fit Chamley's
climatic model more closely.
C1inopti1o1ite is a Na and K zeolite that forms under
conditions of high silica concentration and high pH. Most
c 1 i nopti 1 o1ite crystallizes from aqueous solutions where
chemical activities of base cations. Si, and water influence
the type of zeolite that will precipitate (Hay, 1966; Boles
and Wise, 1 97 8 ). According to Hay, H ions compete with
cations for the aluminosilicate framework. Therefore, high
ratios of cations to H ions tend to cause a high pH which is
essential for zeolite formation. Hay specified that the
permeability must be relatively low in order to allow cations
to stay in place long enough for the reactions to occur.
The present study found that c1inopti1o1ite occurs as
individual crystals in the silt and clay fraction (finer than
40). It was not clear whether the individual euhedral
crystals (Plate 4) were authigenic or detrital. Rooney and
Kerr (1964) found clusters of zeolite crystals in the Fungo
75
River Formation sediments in Aurora. Lack of clusters and
broken individual crystals scattered throughout the matrix
suggest that the grains have been transported. Waters (1983)
and Hale and Spruill (pers. comm., 1983) found c1inopti1o1ite
crystals growing as clusters inside foraminifera tests in
some southern Onslow Bay cores, suggesting that
c1inoptilo1ite in certain cores is authigenic. Foraminifera
tests range from fine to very fine sand size and the
c1inoptilo1ite crystals within the foraminifera tests range
from medium silt down to clay size. The crystals in the mud
fraction are of similar size as those in the foraminifera.
Reworking of older sediments may leach away the surrounding
shell, exposing the c1inopti1o1ite clusters which are broken
up into individual crystals, and redispersing them throughout
the sediment. Irregular edges on one side of c1inopti1o1ite
crystals in Plate 4 may be where individual crystals were
broken from the clusters.
High silica concentration in pore waters is required to
form sepiolite and c linoptilo1ite (Isfording, 1973). In the
world ocean silica comes from rivers, pore water refluxes,
and volcanic and biogenic sources (Heath, 1974) (Fig. 16).
On continental shelves, the sources of silica are from
weathering of onshore silicate rocks (Reynolds, 1970),
upwelling of dissolved biogenic silica with a minor
contribution from volcanic sources (Rennet, 1982).
Clinoptilo1ite found in deep sea sediments apparently forms
from silicious organisms (lijima, 1978; Riech and von Rad,
1 97 9 )
76
RIVER INPUT FROM
Figure 16. Cycle of dissolved silica in the oceans. All ç^mbers
represent magnitudes of dissolved silica in 10 grams
Si02/year. Silica sources are in capitals; transfer-
mations (cycling) are in italics; solid phases are
stipled (from Heath, 1974).
77
In Riggs' (1984) continental margin model for
phosphorite sedimentation (Table 8), the main silica sources
could be dramatically different. During low to intermediate
sea-level stands and cooler, drier climates, upwelling should
play a major role in moving deep, silica-rich water onto the
continental margins. Also, leaching of terrestrial silicate
rocks would be at a minimum with relatively low input of
dissolved silica onto the shelves. During the transgressive
event, silia- and P-rich waters would move further across
the shelf. Since transgression is in response to the
development of warmer and more humid climatic conditions,
leaching of silica from terrestrial silicate rocks should
increase as weathering conditions become more lateritic.
During high sea-level stands, the Si content in shelf waters
should be at a maximum, allowing for optimum formation of
authigenic c1inoptilo1ite and sepiolite. Miller (1971) noted
that c1inoptilo1ite is more prominent in phosphate-rich beds
than clay-rich beds. Miller's trend suggests a link between
silica and P which lends itself to the idea of upwelling.
Examination of clay suites reported in the literatures
in the Hawthorn Formation of Florida, Georgia, and South
Carolina and the Pungo River Formation of Onslow and Aurora
embayments, points to some interesting trends. The Hawthorn
and Pungo River Formations are contemporaneous and continous
units which formed in response to a major Miocene
phosphogenic event Riggs, 1984). These units contain an
anomalous suite of clay minerals which consist dominantly of
78
1) attapulgite, sepiolite, and montmori11onite in Florida and
Georgia; 2) attapulgite, sepiolite, and montmorillonite, with
traces of illite and in South Carolina; and 3)
montmori1Ionite, illite, and c1inopti1o1ite, with traces of
sepiolite and chamosite in North Carolina (Fig. 17) (Rooney,
1965; Heron and Johnson, 1966; Weaver and Beck, 1977). If
the Fungo River and Hawthorn Formations are contemporaneous
and continuous, then the changing north to south pattern of
clay distributions indicate a general latitudinal zonation
from sub-tropical climates in the south to more temperate
climates in the north. Sepiolite, which requires warm
climates to form, should decrease as climatic conditions
become more temperate with increasing latitude. Likewise,
increasing amounts of illite with increasing latitude
indicate more temperate climatic conditions.
Weaver and Beck (1977) noted an inverse relationship
between the presence of attapulgite and sepiolite and that of
c1inopti1o1ite in the Hawthorn Formation. No attapulgite
occurs in the Onslow Bay samples; however, with the exception
of two units, the same general inverse relationship occurs
between sepiolite and c1inopti1o1ite (Fig. 18). Hay (1978)
found that the presence of divalent Mg required for sepiolite
formation, restricts the formation of c1inopti1o1ite. If Mg
is the controlling factor, then there might have been some
in Mg concentrations during deposition of the Fungo
River Formation sequences.
79
34°
28°
Figure 17. Generalized trends in clay mineral and zeolite
distribution in Miocene sediments of the southeast
United States. Bulges indicate a NE-SW direction
of increasing abundance from Florida to North
Carolina. (Based on Rooney, 1965; Heron and
Johnson, 1966; Weaver and Beck, 1977; and on data
from this project)
CLINOPTILOLITE SEPIOLITE
P A P i
1 1 1 t
S-5 • •
S-2 * •i
S-1 i i
SERRAVAL 1 CM • •L-1 • •LBUARNDGH B-6 •IGALIAIAN B-5 i '. •tB-3 • • >B-2
B-1
Figure 18. Plot of presence (P) and absence (A)
of cllnoptilolite and sepiolite in
the 3 depositional sequences of the
Pungo River Formation in Onslow Bay.
21))TThe
CONCLUSIONS
heclay component of the Pungo River Formation sedimentsin Onslow Bay consists of varying percentages of: 1)e3x)pCalnadyib,le, well crystallized, mica derived-montmori11 on i tesmectite; 2) poorly crystallized illite characterized byillite polymorphs of Im, Imd, and Imd glauconite; 3) poorlycrystallized sepiolite 4) poorly to moderately well-crystallized kao1inite-type chamosite; and 5) moderatelywe 11-crystal1ized c1inoptilo1ite (zeolite).Burdigalian and Serravallian clay suites arepredominantly smectite with subdordinate illite and minoramounts of chamosite, sepiolite, and c1inopti1o1ite. TheLanghian clay suite is predominantly illite with subordinatesmectite, and a minor amount of sepiolite.Fe and silica, weathered from rocks in the Piedmont
and Coastal Plain regions, were carried to the sea by
fluvial processes, and deposited on the shelf. In addition
to continental sources, dissolved silica from deep marine
waters, moved onto the shelf by oceanic upwelling during
intermediate sea-level stands. During transgression,
upwelled silica, plus Mg, Na, and K from sea water might have
produced authigenic c1inopti1o 1 i t e and sepiolite. The
authigenic nature of c1inopti1o1ite has been established in
the Burdigalian depositional sequences, however, the zeolite
82
m45))iDgRheetgdrbuaecdienddgetrital in the Serravallian depositional sequences.clay material, such as smectite and kaolinite,plus Fe and Mg, might have produced authigenic glauconite andchamo site. conditions in the depositional environment are
indicated by the formation of authigenic c 1 inopti1o1ite,
sepiolite, chamosite, and glauconite.
6) Global climatic changes appear to have had some impact on
the clay mineralogy of the Fungo River Formation in Onslow
Bay. Smectite and illite, the two principal clay mineral
groups, are believed to be directly related to changing
continental climatic weathering conditions. Illites might
have formed from the alteration of micas during periods of
cooler climatic conditions and lower sea-level stands.
Smectites may have formed from the increased weathering of
illites during periods of warmer climatic conditions and
higher sea-level stands.
7) Smectite and illite are the dominant clay minerals inthe
northern portion in the region of the Hawthorn and Fungo
River Formations, while sepiolite and attapulgite are
dominant clays in the southern region. In addition.
83
chamosite and c1inopti1o1ite appear to increase in
concentration in a northward direction.
84
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92
APPEITOIX A. Sieve and pipette data for the Onslow Bay samples.
Sample 1-1 Sample 2-1 Sample 4-1 Sample 6-1 Sample 6-2 Sample 6-3
Diameter Sample 14-1
Ind. Cum. Cum. Cum. Cum.
mm phi Ind. Ind. Ind. Cum. Ind. Cum. Ind. Ind, Cum.(%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
4.0 -2.0 0 0 0 0 1.1 1.1 0 0 0 0 0 0 0 0
0 0 .07 .07 3.0 4.1 0 0 0 0 0 0 0 0
2.0 -1.0 .30 .30 .35 .42 4.5 8.6 1.4 1.4 0 0 0 0 3.9 3.9
.30 .60 .55 .97 4.0 4.6 1.5 2.9 .09 .09 .05 .05 .48 4.4
1.0 0.0 .40 1.0 .63 1.6 10.3 14.9 1.7 4.6 .07 .16 .13 .18 .16 4.5
1.0 2.0 .79 2.4 2.3 17.2 2.9 7.5 .38 .55 .42 .60 .56 5.1
SIEVE .5000 1.0 4.0 6.0 .71 3.1 4.8 22.0 4.3 11.8 .82 1.3 .74 1.3 .76 5.97.7 13.7 1.0 4.1 10.0 32.0 1.1 12,9 2.2 3.5 3.0 4.3 1.3 7.2
.2500 2.0 12.3 26.0 1.1 5.2 8.5 51.5 7.7 30.6 5.5 9.0 2.8 7.1 3.9 11.2
26.1 52.1 2.4 7.6 17.0 68.5 19.9 50.5 8.1 17.1 8.3 15.4 7.7 18.9
.1250 3.0 20.7 72.8 9.0 16.6 5.9 74.4 8.0 58.5 5.6 22.7 2.8 18.2 10.6 29.5
3.4 76.2 36.6 53.2 2.8 77.2 1.5 60.0 1.5 33.2 7.9 26.1 15.4 45.0
.0625 4.0 1.8 78.0 15.2 78.4 4.2 81.4 2.4 62.4 20.9 54.1 17.5 43.6 13.7 58.7
.0625 4.0 81.4 76.9 84.7 62.7 57.5 46.7 60.9
.0310 5.0 6.8 88.2 3.5 80.4 3.2 87.9 7.0 69.7 18.6 76.1 9.6 56.3 15.8 76.7
.0156 6.0 5.4 93.6 3.5 83.9 2.0 89.9 13.6 83.3 8.4 84.5 15.7 72.0 10.1 86.8
w .0078 7.0 2.3 95.9 2.6 86.5 .30 90.2 2.4 85.7 6.5 91.0 8.6 80.6 5.4 92.2H
H
w .0039 8.0 2.0 97.9 .70 87.2 .01 90.2 1.7 88.4 3.9 94.9 7.7 88.3 3.1 95.3
0^
M
CL, .0020 9.0 .50 98.4 .30 87.5 1.0 91.2 1.9 90.3 2.5 97.4 1.8 90.1 1.6 96.9
.00098 10.0 .20 98.6 1.7 89.2 .10 91.3 2.0 92.3 1.7 99.1 3.4 93.5 .60 97 .5
->10.0 1.4 100 10.8 100 8.7 100 7.7 100 .90 100 6.5 100 2.5 100
Sample 20-1 Sample 20-2 Sample 20-3 Sample 22-1 Sample 23-1 Sample 29-1 Sample
Diameter 30-1
Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum.
phi Ind.
Cum.
mm
(%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
4.0 -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 0 0 0 0
2.0 -1.0 0 0 0 0 .35 .35 1.8 1.8 0 0 0 0 0 0
.07 .07 .06 .06 .08 .43 .05 2.3 .31 .31 0 0 0 0
1.0 0.0 .19 .19 .09 .15 .04 .47 .80 3.1 .30 .61 0 0 0 0
.09 .28 .28 .43 .17 .64 1.3 4.4 .35 .96 .05 .05 .09 .09
w
> .5000 1.0 .29 .57 .67 1.1 .46 1.1 2.9 7.3 .64 1.6 .14 .19 .01 .10
M
C/J .21 .78 2.0 3.1 1.3 2.4 9.3 16.6 1.4 3.0 1.1 1.3 .05 .15
.2500 2.0 1.6 2.4 3.1 6.2 3.4 5.8 9.0 25.6 2.5 5.5 1.7 3.0 .04 .19
4.8 7.6 7.0 13.2 9.7 15.5 10.6 36.2 4.7 10.2 2.5 5.5 .64 .83
.1250 3.0 12.8 20.4 16.7 29.9 31.2 46.7 12.5 48.7 7.2 17.4 5.9 11.4 10.8 11.7
5.7 26.1 10.1 40.0 15.7 62.4 10.4 59.1 9.0 26.4 29.5 40.9 27.7 39.4
.0625 4.0 4.1 30.2 8.7 48.7 6.1 68.5 14.7 73.8 11.1 37.5 21.7 62.6 17.1 56.5
.0625 4.0 29.7 46.3 -72.1 76.5 36.2 63.7 58.5
.0310 5.0 16.7 46.4 25.8 72.1 12.9 85.0 3.0 79.5 15.7 51.9 7.8 71.5 6.4 64.9
.0156 6.0 19.2 65.6 14.2 86.3 7.0 92.0 5.7 85.2 20.3 72.2 11.4 82.9 9.2 74.1
w
H .0078 7.0 14.0 79.6 4.5 90.8 .6 92.6 8.2 93.4 6.5 78.7 2.4 85.3 4.4 78.5
H
w .0039 8.0
Cl, 10.2 89.8 2.0 92.8 2.7 95.3 .7 94.1 8.8 87.5 4.4 89.7 7.3 85.8
H
P4 .0020 9.0 .5 90.3 .6 93.4 2.0 97.3 2.0 96.1 2.6 90.1 1.4 92.1 3.6 89.4
.00098 10.0 .7 91.6 .6 94.8 1.4 98.7 .30 96.4 2.3 92.4 1.3 93.4 3.9 93.3
->10.0 8.4 100 5.2 100 1.3 100 3.6 100 7.6 100 6.6 100 6.7 100
Sample 30-2 Sample 30-3 Sample 30-4Diameter Sample
34-1 Sample 35-1 Sample 42-1 Sample 44-1
Ind. Cum.
phi Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum.mm (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
4.0 -2.0 0 0 0 0 1.4 1.4 0 0 0 0 0 0 0 0
0 0 0 0 .30 1.7 0 0 0 0 0 0 0 0
2.0 -1.0 .14 .14 0 0 .30 2.0 0 0 .07 .07 .15 .15 2.6 2.6
.90 .23 0 0 .30 2.3 .04 .04 .10 .17 .15 .30 1.4 4.0
1.0 0.0 .18 .41 0 0 .40 2.7 .01 .05 .19 .36 .24 .54 1.1 5.1
.50 .91 .01 .01 1.0 3.7 .12 .17 .25 .61 .46 l'.O 3.9 9.0
w
> .5000 1.0 .99 1.9 .01 .02 1.8 5.5 1.0 1.2 .35 .96 1.1 2.1 6.4 15.4
H
in i.8 3.7 .01 .03 2.5 8.0 4.8 6.0 .54 1.5 4.4 6.5 6.7 22.1
.2500 2.0 5.3 9.0 .11 .14 5.4 13.4 15.3 21.3 2.2 3.7 3.8 10.3 6.4 28.5
9.6 19.4 .61 .75 9.1 22.5 15.4 36.7 6.2 9.9 6.6 16.9 6.9 35.4
.1250 3.0 14.0 33.4 15.0 15.8 13.1 35.6 6.6 43.3 10.0 19.9 5.7 22.6 9.0 44.4
8.9 52.3 17.2 43.0 19.2 56.8 2.0 45.3 5.3 25.2 6.2 28.8 3.3 47.7
.0625 4.0 15.8 68.1 14.4 57.4 46.5 75.4 .90 46.5 6,6 31.8 15.6 44.4 1.0 48.7
.0625 4.0 71.6 58.0 77.3 43.5 29.1 48.7 50.0
.0310 5.0 11.0 80.6 13.8 71.8 3.5 80.8 4.9 48.4 28.7 57.8 28.8 76.5 3.9 53.9
.0156 6.0 9.9 90.5 3.1 74.9 4.0 84.8 3.4 51.8 14.9 82.7 9.7 86.2 8.0 61.9
w
H .0078 7.0 4.2 94.7 4.9 79.8 3.5 88.3 11.9 63.7 7.1 89.8 6.4 92.6 4.8 76.7
W .0039 8.0
CL, 1.9 96.6 6.8 86.6 5.8 94.5 12.9 76.6 3.4 93.2 2.4 95.0 8.1 84.8
M
Pu .0020 9.0 .5 97.1 5.7 92.3 2.9 97.4 5.4 82.0 3.1 96.3 2.0 97.0 4.4 89.2
.00098 10.0 .2 97.3 3.2 95.5 2.1 99.5 4.7 86.7 1.3 97.6 .6 97.6 4.8 94.0
•>10.0 2.7 100 4.5 100 .5 100 13.3 100 2.4 100 2.4 100 6.0 100
Sample 44-2 Sample 44-3 Sample 45-1 Sample 45-2 Sample 45-3 Sample47-1 Sample48-1Diameter
Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum.
mm phi (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
4.0 -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 0 0 0 0
2.0 -1.0 1.4 1.4 0 0 2.7 2.7 2.8 2.8 2.3 2.3 .06 .06 .20 .20
2.4 2.4 0 0 3.5 6.2 2.2 5.0 3.0 5.3 .09 .15 .13 .33
1.0 0.0 1.0 3.4 .01 .01 3.9 10.1 1.7 6.7 2.2 7.5 .09 .24 .18 .51
1.8 5,6 .08 .09 4.4 14.5 2.6 9.3 4.0 11.5 .35 .59 .25 .76
SIEVE .5000 1.0 2.7 8.3 .15 .24 4.0 18.5 8.4 17.7 9.1 20.6 .01 .60 .34 1.12.8 11.1 .16 .40 5,2 23.7 22.9 40.6 20.1 40.7 .03 .63 .70 1.8
.2500 2.0 4.6 15.7 .80 1.2 7.2 30.9 35.7 76.3 25.7 66.4 .04 .67 1.9 3.7
10.5 26.2 11.4 12.6 10.4 41.3 13.3 89.6 8.7 75.1 .11 .78 18.5 22.2
.1250 3.0 25.6 51.8 22.5 35.1 13.0 54.3 4.3 93.9 3.0 78.1 1.2 2.0 53.0 75.2
1.8 53.6 1.3 36.4 3.4 57.7 .80 94.7 .90 79.0 5.3 7.3 8.1 83.3
.0625 4.0 .50 54.1 1.2 37.6 1.7 59.4 .60 95.3 .50 79.5 6.8 14.1 1.3 84.6
.0625 4.0 68.5 35.4 63.7 96.3 78.1 15.3 84.0
.0310 5.0 5.5 74.0 4.8 40.2 17.5 81.2 1.0 97.3 4.1 82.2 9.6 24.9 4.3 88.3
.0156 6.0 7.5 81.5 8.1 48.3 6.7 87.9 1.3 98.6 5.9 88.1 10.8 35.7 4.1 92.4
H .0078 7.0 5.4 86.9 7.3 55.6 5.2 93.1 1.0 99.6 6.2 94.3 9,0 44.7 3.9 96.3
W .0039 8.0
CU 6.4 93.3 13.7 69.3 2.7 95.8 .20 99.8 ,30 94.6 15.7 60.4 1.8 98.1
Pm .0020 9.0 1.6 94.9 8.3 77.6 2.1 97.9 ,001 99.8 1.0 95.6 14.5 74.9 .80 98.9
.00098 10.0 .70 95.6 8.9 96.5 .001 97.9 .001 99.8 .001 95.6 11.3 86.2 .50 99.4
->10.0 4.4 100 3.5 100 2.1 100 .20 100 4.4 100 13.8 100 .60 100
3Sample 51-1Diameter Sample 52-] Sample53_-i Sample 53_2 Sample 53 Sample 57-1 Sample 60-1
Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum.
phi Ind. Cum.mm (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)
4.0 -2.0 0 0 0 0 .15 .15 0 0 .95 .95 0 0 0 0
0 0 0 0 .17 .32 .01 .01 .80 1.3 0 0 .21 .21
2.0 -1.0 0 0 1.7 1.7 .14 .46 .14 .15 .30 1.6 0 0 .18 .39
.02 .02 .40 2.1 .33 .79 .76 .91 .30 1.9 0 0 .38 .77
1.0 0.0 .07 .09 .60 2.7 .91 1.7 1.5 2.4 .50 2.4 0 0 2.0 2.8
.21 .30 .70 3.4 3.6 5.3 3.8 6.2 1.1 3.5 .002 .002 8.3 11.1
w
> .5000 1.0 .67 .97 1.6 5.0 11.7 17.0 6.5 12.7 1.7 5.2 .002 .004 10.1 21.2
M
C/D 2.2 3.2 1.6 6.6 18.7 35.7 10.0 22.7 2.6 7.8 .08 .08 5.2 26.4
.2500 2.0 13.1 16.3 1.8 8.4 15.1 50.8 16.6 39.3 4.4 12.2 .14 .22 3.7 30.1
40.6 56.9 1.7 10.1 12.6 63.4 23.8 64.1 8.2 20.4 2.2 2.4 6.5 36.6
.1250 3.0 19.0 75.9 2.5 12.6 7.2 70.6 13.2 77 .3 17.8 38.2 15.2 17.6 3.7 40.3
2.7 78.6 2.3 14.9 3.2 73.8 2.7 80.0 12.4 50.6 34.7 52.3 1.2 41.5
.0625 4.0 1.1 79.7 3.1 18.0 2.6 76.4 1.8 81.8 4.4 55.0 21.7 74.0 1.2 42.7
.0625 4.0 75.6 15.6 77.8 82.1 51.2 72.0 45.2
.0310 5.0 4.0 79.6 15.9 31.5 1.9 79.7 1.1 83.2 7.0 58.2 3.9 76.1 .60 45.8
.0156 6.0 5.5 85.1 3.5 35.0 3.0 82.7 1.1 84.3 4.5 62.7 5.7 81.8 3.9 49.7
w
H .0078 7.0 5.8 90.9 25.6 60.6 2.3 85.0 1.6 85.9 6.8 69.5 7.2 89.0 8.0 57.7
H
w .0039 8.0
(X .90 91.8 23.2 83.8 1.6 86.6 3.3 89.2 13.0 82.5 4.8 93.8 3.9 61.6
PM .0020 9.0 .50 92.3 5.1 88.9 2.2 88.8 .60 89.8 1.3 83.8 1.8 95.6 9.2 70.8
.00098 10.0 1.1 93.4 4.4 93.3 1.6 90.4 .50 90.3 3.3 87.1 1.1 96.7 17.7 87 .9
->10.0 6.6 100 6.7 100 9.6 100 9.7 100 12.9 100 3.3 100 12.1 100
Sample 62-1 Sample 63-1 Sample 66-1 Sample 67-1
Ind. Cum. Ind. Cum. Ind. Cum. Ind. Cum.
mm phi (%) (%) (%) (%) (%) (%) (%) (%)
A.O -2.0 7.3 7.3 0 0 0 0 0 0
4.1 11.4 0 0 0 0 0 0
2.0 -1.0 3.9 15.3 0 0 .07 .07 .04 .04
3.3 18.6 6.5 6.5 .34 .41 .04 .08
1.0 0.0 2.1 20.7 3.9 10.4 .79 1.2 .04 .12
4.7 25.4 4.1 14.5 .40 1.6 .16 .28
w
> .5000 1.0 3.6 29.0 3.4 17.9 3.1 4.7 .52 .80
w
M
C/Ü 1.2 31.8 4.6 22.5 5.2 9.9 1.5 2.3
.2500 2.0 4.9 36.7 5.4 27.9 5.9 15.8 4.6 6.9
17.5 54.2 6.6 34.5 10.0 25.8 7.3 14.2
.1250 3.0 26.2 80.4 8.0 42.5 14.8 40.6 14.2 28.4
9.4 89.5 6.3 48.8 10.2 50.8 39.0 67.4
.0625 4.0 4.1 93.6 5.5 54.3 5.4 56.2 10.6 78.0
.0625 4.0 95.7 53.4 58.7 80.5
.0310 5.0 1.6 97.3 7.3 66.7 4.6 63.3 1.6 82.1
.0156 6.0 1.1 98.4 11.5 78.2 5.6 68.9 1.7 83.8
pa
H .0078 7.0 .20 98.6 10.5 88.7 4.1 73.0 1.6 85.4
H
W
P4 .0039 8.0 .30 98.9 3.4 92.1 2.5 75.5 1.9 87.3
1—1
.0020 9.0 .10 99.0 1.4 93.5 11.0 86.5 1.8 89.1
.00098 10.0 .40 99.4 1.8 95.3 1.9 88.4 1.2 90.3
10.0 .60 100 4.7 100 11.6 100 9.7 100
VO
C»
99
APPENDIX B. Staining technique for thin section study.
100
110..REtch the polished surface for 10 to 15 seconds in concentrated (52%)hydrofluoric acid.2. Dip the thin section in water.3. Immerse the thin section in a saturated solution of sodium cobalti-nitrite for 1 minute.4. Wash the thin section in tap water to remove excess cobaltinitrite.5. Allow thin section to air dry.6. Immerse the thin section for 15 seconds in 5% barium chloride solu-ti7. Demonipov.the thin section once quickly in water and allow to air dry.8. Immerse the thin section for 16 seconds in Amaranth red solution (1ounce of 92% pure coal-tar dye in 2 liters of water).9. Dip thee thin section once quickly in water.excess dye from the surface of the thin section by shaking
vigorously.
Table B: Staining technique for thin section study (from Carver,
1971).
101
APPENDIX C. Cumulative probability curves for the Onslow Bay samples.
102
CPSUREMCORUB-CLAABETILNIIVETTEY
Figure C-1: Cumulative probability curves for the lower
portion of the Burdigalian depositional se-
quence. Percentiles were taken from the curves
curves for the statistical parameter for-
muías.
103
GRAIN SIZE (phi)
Figure C-2: Cumulative probability curves for lower portion
of the Burdigalian depositional sequence. Per-
centiles were taken from the curves for statisti-
cal parameter formulas.
104
CSPUREMCORUB-LACABLETILIENIVTEYT
GRAIN SIZE (phi)
Figure C-3: Cumulative probability curves for the upper portion
of the Burdigalian depositional sequence. Percen-
tiles were taken from the curves for the statistical
parameter formulas.
99 •
SPCPRUCEOMRB-UACLBAEILTNITEIVYTE
* I 1 I ' I I , I
-2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
GRAIN SIZE (phi)
Figure C-4: Cumulative probability curves for the Langhian
depositional sequence. Percentiles were taken
from the curves for the statistical parameter
formulas.
SPPRCEOUBRM-ACUBLEIALNITETIYVTE
GRAIN SIZE (phi)
Figure C-5: Cumulative probability curves for the lower
portion of the Serravallian sequence. Per-
centiles were taken from the curves for the
statistical parameter formulas.
SPPCRCUEOMBR-AUCBLEIALINTTEIYTVE
GRAIN SIZE (phi)
Figure C-6: Cumulative probability curves for the lower
portion of the Serravallian sequence. Per-
centiles were taken from the curves for the
statistical parameter formulas.
APPENDIX D. Formulas used for computing the statistical parameters
109
Graphie Mean (M^,) :
M2=(016 + 050 + 084) / 3
Inclusive Graphie Standard Deviation (erj^) :
(Tl = 084 - 016 + 095 - 05
4 6.6
Inclusive Graphie Skewness (Sk;[^) :
Sk^ = 016 + 084 - 2(050) + 05 + 095 - 2(050
2(084 - 016) 2(095 - 05)
Kurtosis (Kg):
K = 095 - 05
® 2.44 (075 - 025)
Mode (Mo):
"Using the graph of the sample plotted on probability paper,
one selects a point where the mode ought?to be, and measures
the percentage of the sample that occurs within the diameter
range from 1/40 coarser than that point to 1/4 0 finer than
than that point (i.e. within 1/2 0 interval centered on the
presumed modal point). Then he moves over a small distance
(say 0.1 or 0.2 0) to a new presumed mode and measures the
percentage occurring in the 1/20 interval centered on that
new point. This is done repeatedly until the highest value
is obtained which then corresponds to the modal diameter."
(Folk, 1980)
Table D. Statistical parameters used for the textural analysis
(from Folk, 1980).
APPENDIX E, Maturity diagram for textural analysis.
IMMATURE
SUBMATURE
MATURE
SUPERMATURE
Figure E. Maturity classification scheme used for the textural samples.
a= sorting; p= roundness (from Scholle, 1979).
Ill
112
APPENDIX F Textural data for samples selected from the Serravallian,
Langhian, and Burdigalian depositional sequences.
UNIT CORE SAMPLE DEPTH TERRIGENOUS SAND SILT CLAY COLOR
(m) (%) (%) (%) (%)
B-1 20 1 1.00-1.25 14 30 59 11 Olive Gray - 5Y 3/2
B-1 20 2 3.50-3.75 28 49 44 7 Olive Gray - 5Y 3/2
B-1 20 3 5.50-5.75 67 68 26 6 Olive Black - 5Y 2/2
B-1 23 1 2.00-2.25 23 37 50 13 Olive Black - 5Y 2/1
B-1 29 1 2.75-3.00 42 62 27 11 Olive Gray - 5G 3/2
B-1 14 1 4.75-5.00 23 60 35 5 Olive Gray - 5Y 4/1
B-1 22 1 4.75-5.00 29 74 20 6 Olive Black - 5Y 2/2
B-1 30 1 1.00-1.25 39 56 29 15 Olive Black - 5Y 2/2
B-1 30 2 1.75-2.00 46 68 28 4 Olive Black - 5Y 2/2
B-1 30 3 2.50-2.75 64 75 19 6 Olive Black - 5Y 2/2
B-1 30 4 5.00-5.25 43 57 29 14 Light Olive Gray - 5Y 5/2
avg. 14* 21* 43 62 27 11
Table F-1: Textural data for the lower portion of the Burdigalian depositional sequence. Sample
depths are measured down from the top of each core. Terrigenous percentages are from
thin section point counts. Sand, silt, and clay percentages are from sieve and pipette
data. Color is based on Goddard and others (1975). *= denotes total number of cores
and samples studied in the Burdigalian sequence. 113
UNIT CORE SAMPLE MEAN PHI SORTING SKEWNESS KURTOSIS MATURITY MODES
(0)
PQ 1 20 1 m silt 4.7 X poor .21 fine 1.1 mesokurtic immature 3;6;8
B-l 20 2 4.1 c silt 3.8 V poor .25 fine 1.4 leptokurtic immature 3;5
B-1 20 3 3.5 vf sand 3.3 V poor .55 s fine 1.5 leptokurtic immature 3;5
B-l 23 1 5.1 m silt 4.7 X poor .30 fine 1.5 leptokurtic immature 6
B-l 29 1 4.4 c silt 4.5 X poor .70 s fine 1.8 V leptokurtic immature 3.5
B-l 14 1 3.9 vf sand 3.3 V poor .18 fine 1.4 leptokurtic immature 3.5;5
B-l 22 1 3.5 vf sand 3.2 V poor .32 s fine 1.4 leptokurtic immature 1.5;3;4
B-l 30 1 4.9 c silt 4.8 X poor .74 s fine 1.1 mesokurtic immature 3.5;6
B-l 30 2 3.7 vf sand 3.3 V poor .32 s fine 1.2 leptokurtic submature 3.5;6
B-l 30 3 3.8 vf sand 2.0 poor .37 s fine 2.1 V leptokurtic immature 3.5;7
B-l 30 4 4.8 c silt 4.6 X poor .73 s fine .92 mesokurtic immature 3.5;5
avg. 14* 21* 3.9 vf sand 3.5 V poor .41 s fine 1.7 V leptokurtic
Table F-l(cont Textural data for the lower portion of the Burdigalian depositional sequence,. f= fine;
vf= very fine; m= medium; c= coarse ; v= very; x= extremely; s= strongly. *= denotes
the total number of cores and samples studied in the Burdigalian.
114
UNIT CORE SAMPLE DEPTH TERRIGENOUS SAND SILT CLAY COLOR
(m) (%) (%) (%) (%)
B-6 45 1 1.75-2.00 15 59 36 5 Olive Gray - 5Y 4/1
B-6 45 2 3.50-3.75 40 95 4 1 Olive Gray - 5Y 4/1
B-6 45 3 5.00-5.25 80 79 15 6 Olive Gray - 5Y 4/1
B-6 62 2 4.25-4.50 50 93 6 1 Olive Gray - 5Y 4/1
B-6 66 1 3.00-3.25 83 56 19 25 Olive Gray - 5Y 3/2
B-6 67 1 3.50-3.75 35 78 9 13 Light Olive Gray - 5Y 3/2
B-5 57 1 4.75-5.00 78 74 19 7 Olive Black - 5Y 2/2
B-3 48 1 4.00-4.25 69 85 13 2 Olive Gray - 5Y 3/2
B-2 47 1 5.00-5.25 23 12 47 41 Grayish Olive - lOY 4/2
B-2 63 1 2.25-2.50 22 54 37 9 Greenish Black - 5G 2/1
Table F-2: Textural data for the upper portion of the Burdigalian depositional sequence. Sample depths
are measured down from the top of the core. Terrigenous percentages are from thin section
point counts. Sand, silt, and clay percentages are from sieve and pipette data. Color
codes are from Goddard and others (1975).
SORTING SKEWNESS KURTOSIS MATURITY
MODES
UNIT CORE SAMPLE MEAN PHI (0)
B-6 45 1 3.0 f sand 2.8 V poor .25 s fine 1.0 mesokurtic
immature 3;5
B-6 45 2 1.6 m sand 1.4 poor .16 fine 2.1 V leptokurtic submature
2
immature 2
B-6 45 3 2.8 f sand 3.1 V poor .68 s fine 2.9 V leptokurtic
B-6 62 2 2.1 f sand 1.7 poor -.11 coarse .64 V platykurtic
submature 3
immature 3
B-6 66 1 4.7 c silt 3.1 V poor .57 s fine .81 mesokurtic
silt 2.5 1.0 s fine 4.6 X leptokurtic immature 3.5B-6 67 2 4.6 c V poor
B-5 57 1 4.2 c silt 4.1 X poor .70 s fine 2.9 V leptokurtic immature 3.5;7
B-3 48 1 3.0 f sand 2.9 V poor .68 s fine 3.7 X leptokurtic
submature 3
B-2 47 1 7.0 f silt 5.7 X poor -.06 sym .85 platykurtic immature 5;8
B-2 63 1 3.6 vf sand 3.4 V poor .17 fine .94 mesokurtic
immature 3
Table F-2 (cont Textural data for the upper portion of the Burdigalian depositional sequence, f= fine;
vf= very f ine ; in= medium; c= coarse; v= very; x= extremely; s= strongly; sym= symmetric
116
UNIT CORE SAMPLE DEPTH TERRIGENOUS SAND SILT CLAY COLOR
(m) (%) (%) (%) (%)
L-2 34 1 2.00-2.25 27 47 30 23 Olive Gray - 5Y 3/2
L-2 52 1 3,50-3.75 61 18 66 16 Grayish Olive: - 10 4/2
L-1 35 1 3.75-4.00 12 32 61 7 Medium Olive - 5Y 5/1
Gray
L-1 44 1 1.75-2.00 30 49 35 16 Olive Gray - 5Y 4/1
L-1 44 2 3.00-3.25 43 54 39 7 Medium Olive - 5Y 4/2
Gray
L-1 44 3 5.50-5.75 57 37 31 32 Olive Gray - 5Y 3/2
L-1 51 1 4.00-4.25 75 80 12 8 Olive Gray - 5Y 3/2
avg. 5* 7* 43 45 39 16
Table F-3: Textural data for the Langhian depositional sequence. Sample depths are measured down from
the top of each core. Terrigenous percentages are from thin section point counts. Sand,
silt, and clay percentages are from sieve and pipette data. Color is based on Goddard and
others (1975). *= denotes total number of cores and samples studied for the Langhian
sequence.
UNIT CORE SAMPLE MEAN PHI SORTING SKEWI'IESS KURTOSIS MATURITY MODES
(0)
L-2 34 1 5.7 m silt 4.9 X poor .12 fine .74 platykurtic immature 2.2;5
L-2 52 1 6.0 m silt 4.7 X poor .07 sym 1.5 leptokurtic immature 5;7
L-1 35 1 4.6 c silt 3.9 V poor .04 sym 1.3 leptokurtic immature 3;5
L-1 44 1 4.5 c silt 3.7 V poor .05 sym .78 platykurtic immature 3;7
L-1 44 2 3.8 vf sand 3.7 V poor .56 s fine 1.5 leptokurtic immature 3;6
L-1 44 3 5.8 m silt 4.6 X poor -.17 coarse .55 V platykurtic immature 3;6
L-1 51 1 3.2 vf sand 3.7 V poor .75 s fine 4.2 X leptokurtic immature 2;5
avg. 5* 7* 4.8 c silt 4.2 X poor .20 fine 1.5 leptokurtic
Table F-3 (cont.): Textural data for the Langhian depositional sequence. f= fine; vf= very fine; m= medium;
c= coarse; v= very; sym= symmetric; x= extremely; s= strongly. *= denotes total num-
ber of cores and samples studied in the Langhian sequence.
UNIT CORE SAMPLE DEPTH TERRIGENOUS SAND SILT CLAY COLOR
(m) (%) (%) (%) (%)
S-5 1 1 5.00-5.25 53 76 10 14 Grayish olive - lOY 4/2
S-2 53 1 1.25-1.50 61 78 20 Oc. Greenish Black - 5GY 2/1
S-2 53 2 3.75-4.00 57 82 7 11 Greenish Black - 5GY 2/1
S-2 53 3 5.25-5.50 48 55 28 17 Greenish Black - 5GY 2/1
S-2 60 1 5.50-6.00 42 42 20 40 Olive Gray - 5Y 4/1
S-1 2 1 4.50-4.75 82 78 8 14 Olive Gray - 5Y 3/2
S-1 4 1 5.50-5.75 76 81 9 10 Olive Gray - 5Y 3/2
S-1 6 1 0.50-0.75 74 62 26 12 Olive Black - 5Y 2/1
S-1 6 2 3.00-3.25 79 54 41 5 Olive Black - 5Y 2/1
S-1 6 3 7.25-7.50 64 44 45 11 Olive Black - 5Y 2/1
S-1 42 1 2.50-2.75 43 44 51 5 Olive Gray - 5Y 3/2
avg. 7* 11* 58 64 24 12
Table F-4: Textural data for the Serravallian deposltional sequence. Sample depths are measured down
from the top of each core. Terrigenous percentages are from thin section point counts.
Sand, silt, and clay percentages are from sieve and pipette data. Color codes are from
Goddard and others (1975). *= denotes total number of cores and samples studied in the 119
Serravallian sequence.
MODES
UNIT CORE SAMPLE MEAN PHI SORTING SKEWNESS KURTOSIS MATURITY (0)
S-5 1 1 2.8 f sand 4.1 X poor 2.8 s fine 2.9 leptokurtic submature 2.5;5
S-2 53 1 3.8 vf sand 4.2 X poor .67 s fine 1.6 V leptokurtic immature 1.5
S-2 53 2 3.2 vf sand 3.7 V poor .63 s fine 3.4 X leptokurtic immature 2.5
S-2 53 3 6.5 m silt 6.0 X poor 2.8 s fine .90 platykurtic immature 3
S-2 60 1 5.4 m silt 4.4 X poor -.10 coarse .65 V platykurtic immature 1;2.5
S-1 2 1X 4.1 c silt 4.3 V poor .67 s fine 5.1 X leptokurtic immature 3.5
S-1 4 1 2.2 f sand 3.0 V poor .43 s fine 2.5 V leptokurtic immature -1;2
S-1 6 1 3.7 vf sand 3.4 V poor .54 s fine .90 platykurtic immature 1;2.5;6
S-1 6 2 4.1 c silt 3.7 V poor .27 s fine 1.5 leptokurtic immature 2.5;4;5
S-1 6 3 4.8 c silt 4.4 X poor .33 s fine 1.3 leptokurtic immature 2.5;4;6
S-1 42 1 4.1 c silt 3.4 V poor .03 sym 1.6 V leptokurtic immature 2.5;7
avg. 7* 11* 3.5 vf sand 4.1 X poor 1.4 s fine 2.2 V leptokurtic
Table F-4 (cont.): Textural data for the Serravallian depositional sequence. f= fine; v= very; vf= very
fine; m= medium; c= coarse; x= extremely; s= strongly; sym= symmetric; *= denotes
the total number of cores and samples studied in the Serravallian sequence.
120
121
APPENDIX G Ternary diagrams of sand-silt-clay percentages for the
samples selected for textural study.
122
>-
<
ü
SRILAT:TMIUOD
W
Figure G-1: Ternary diagram of sand, silt, and clay percentages for
the Burdigalian depositional sequence. Circled dot is
the average sand-silt-clay value for the sequence which
also corresponds to the value for sample 29-1.
123
>-
<
SAND RSIALTT:MIUOD
Figure G-2: Ternary diagram of sand, silt, and clay percentages for
the Langhian depositional sequence. Circled dot is the
average sand-silt-clay value for the sequence. Classifi-
cation is from Folk (1980).
124
SAND SRILAT:TMIUOD
CO
Figure G-3: Ternary diagram of sand, silt, and clay percentages for the
Serravalllan depositional sequence. Circled dot is the
average sand-silt-clay value for the sequence. Classifi-
cation is from Folk (1980).
125
APPENDIX H Point count data from samples selected from the Burdi-
galian, Langhian, and Serravallian depositional sequences.
UNIT CORE SAMPLE Qu Ks Un Tw Mi Zr Ca Rh Sh Sf Ph Cr Cs Op G1 Ch Ma
3-1 20 1 11 2 - 2 1 - - - 12 11 3 - - - 1 - 57
B-1 20 2 25 1 - - 2 - 2 - 7 4 9 - - - 1 - 49
B-1 20 3 66 - - 1 - - - - - 6 4 - - - - - 23
B-1 23 1 29 1 - - T - - - 13 13 34 - - T T - 8
B-1 29 1 41 2 1 2 T - - - 8 6 3 1 - 4 T - 31
B-1 14 1 21 2 T T T - - T - - T - - - T - 74
B-1 22 1 24 1 1 1 1 T - T 8 2 33 - - - T T 27
B-1 30 1 34 1 2 T T - - 2 - T 26 - - T T - 32
B-1 30 2 40 2 2 1 1 T - T - - 25 - - - T - 27
B-1 30 3 59 1 2 2 T - T - T - 15 - - T 1 - 18
B-1 30 4 37 5 1 - T - 4 4 - - T - - 1 T - 46
Table H-1: Point count data in percent for samples from the lower portion of the Burdi-
galian sequence. Qu= quartz; Ks= potassium feldspar; Un= untwinned feldspar;
Tw= twinned feldspar; Mi= muscovite mica; Zr= zircon; Ca= calcite; Rh= dolo-
mite rhombs; Sh= shells; Sf= shell fragments; Ph= phosphate; Cr= clay rims;
Cs= clay clasts; 0p= opaques; Gl= glauconite; Ch= chert; Ma= matrix; T= trace
or <1%.
126
UNIT CORE SAMPLE Qu Ks Un Tw Mi Zr Ca Rh Sh Sf Ph Cr Cs Op G1 Ch Ma
B-6 45 1 15 T 6 T 4 9 - - - 1 - -- - - - 63
B-6 45 2 35 5 T T - 1 - - 1 - - 1 - -- - 56
B-6 45 3 76 3 1 T - - - T - 1 1 T - 1 - - 16
B-6 62 2 51 1 1 T - T 1 2 3 - - - 2 - -- 38
B-6 66 1 79 3 T T - - - - - - 3 - - T - T 13
B-6 67 1 32 3 - - - - 4 - 39 12 T - - T - 1 8
B-5 57 1 67 6 2 2 T - - - - - T - - - - - 22
B-3 48 1 71 - T - -- - - - - - - - 2 - 1 25
B-2 47 1 21 - - 2 - - T T - - - - - T T - 74
B-2 63 1 16 3 1 3 - - - 1 21 10 5 - - T - - 40
avg. 14* 21* 40 2 T T T T T T 5 4 8 T T T T T 36
Table H-1 (cent.): Point count data in percent for samples from the upper portion of
the Burdigalian depositional sequence. *= denotes total number of
cores and samples studied in the Burdigalian sequence. Qu= quartz;
Ks= potassium feldspar; Un= untwinned feldspar; Tw= twinned feld-
spar; Mi= muscovite mica; Zr= zircon; Ca= calcite; Rh= dolomite
rhombs; Sh= shells; Sf= shell fragments; Ph= phosphate; Cr= clay
rims; Cs= clay clasts; 0p= opaques; Gl= glauconite; Ch= chert;
Ma= matrix; T= trace or <1%.
127
UNIT CORE SAMPLE Qu Ks Un Tw Mi Zr Ca Rh Sh Sf Ph Cr Cs Op Cl Ch Ma
L-2 34 1 22 2 T T T
-
- - T T T - - T T - 72
- - --
- -
L-2 52 1 58 2 2 T - 2 1
- 8 27-
-
- -
-
- T
L-1 35 1 10 - 87- - - - - 1 1 T
- - -- -
- - T
L-1 44 1 14 2 T - - T 82- -
-
-
44 2 37 4 1 T - 2 -
- - 2 T T T 52L-1 -
-
L-1 44 3 50 4 2 T T - 5
-
- - 4 T 1 T- 31
- - -
-
- --
L-1 51 1 69 2 1 - T - - 1 1 25
5* 7* 37 2 T T T - T 1 T 1 1 T T T T T 53avg.
Table H-2: Point count data In percent for samples from the Langhian depositional
sequence. *= denotes total number of cores and samples studied in the
Langhian sequence. Qu= quartz; Ks= potassium feldspar; Un= untwinned
feldspar; Tw= twinned feldspar; Mi= muscovite mica; Zr= zircon; Ca= cal-
cite; Rh= dolomite rhombs; Sh= shells; Sf= shell fragments; Ph= phosphate;
Cr= clay rims; Cs= clay clasts; 0p= opaques; Gl= glauconite; Ch= chert;
Ma= matrix; T= trace or <1%.
128
UNIT CORE SAMPLE Qu Ks Un Tw Mi Zr Ca Rh Sh Sf Ph Cr Cs Op G1 Ch Ma
S-5 1 1 52 1 - -- - - - - 8 - - 8 - 1 1 29
S-2 53 1 59 1 - - - - -- - - - - - 1 2 1 36
S-2 53 2 55 1 T T - - T T T 21 - - - -- T 19
S-2 53 3 46 T - - T - 3 - 3 11 24 - - - T - 12
S-2 60 1 40 T 1 - - - - - - T 1 - - -- - 57
S-1 2 1 76 3 -- - 1 T - - - - T 5 T 2 2 8
S-1 4 1 74 1 T -- - - - - 1 3 3 - T T - 16
S-1 6 1 60 2 T T 1 - 5 1 - 2 9 5 - T T T 12
S-1 6 2 63 3 3 2 2 T 2 T - - 5 3 - T T T 15
S-1 6 3 56 2 1 2 2 - T - - - 7 T 6 T T T 22
S-1 42 1 40 1 T T T -- - T - - 4 T T T 1 50
avg. 7* 11* 56 2 T T T T 1 1 T 1 8 1 T T T T 25
Table H-3: Point count data in percent for samples from the Serravallian depositional
sequence. *= denotes total number of cores and samples studied in the
Serravallian sequence. Qu= quartz; Ks= potassium feldspar; Un= untwinned
feldspar; Tw= twinned feldpsar; Mi= muscovite mica; Zr= zircon; Ca= calcite;
Rh= dolomite rhombs; Sh= shells; Sf= shell fragments; Ph= phosphate; Cr= clay
rim; Cs= clay clasts; 0p= opaques; Gl= glauconite; Ch= chert; Ma= matrix;
T= trace or <1%. 129