Geological Sciences
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Item Embargo LATE PLEISTOCENE PALEOENVIRONMENTAL CHANGES IN THE LOWER NEUSE RIVER BASIN, NORTH CAROLINA, AND IMPLICATIONS FOR RELATIVE SEA LEVEL AND COASTAL EVOLUTION(East Carolina University, August 2024) King, Jessica LynnThe coastal plain of eastern North Carolina evolved through the changes associated with late Pleistocene rapid relative sea-level oscillations during Marine Isotope Stages 5 to 2. The sea-level highstand deposits of MIS 5 and MIS 3 have been previously studied in eastern North Carolina; however, certain regions have had little to no data collected, which makes determining the areal extent of facies and associated depositional environments challenging. To overcome these limitations and better understand the spatial and temporal variation of sea-level fluctuations, geophysical and geological data from the lower Neuse River Basin have been analyzed. These data reveal the presence of multiple paleoenvironments with distinctive sequences corresponding to MIS 5e, MIS 5a, and MIS 4. The chronological framework, determined using optically stimulated luminescence dating, provides sediment age estimates ranging from 123.5 (± 7.2) ka to > 56.8 (± 4.1) ka. DS-5e is composed of eastward thickening shelly sand lithofacies. This sequence contains two distinct foraminiferal assemblages. Samples dominated by Elphidium excavatum, Ammonia parkinsoniana, and Elphidium mexicanum are overlain by samples also containing Buccella inusitata, Nonionella atlantica, and Rosalina sp. Additionally, pollen samples collected within DS-5e show a trend of cooler conditions in the lowermost sample of the core to likely warmer than modern conditions in the uppermost collected sample. This transition from low to higher diversity foraminifera assemblages, warming climate conditions, and shelly marine deposits is indicative of a transgressive environment, interpreted as a high salinity estuary becoming an inner shelf environment. DS-5a is characterized by burrowed laminated sand, as well as sandy mud and is barren of foraminifera, with the exception of one sample. Lithofacies show an upward-fining succession transitioning from flaser to wavy tidal bedding. One pollen sample from DS-5a suggests conditions ranging from modern to slightly warmer than present. With apparent tidal bedding, the absence of foraminifera, and warm climate conditions DS-5a is potentially indicative of coastal tidal flat deposits. The lithofacies of DS-4 are characterized by medium to fine-grained burrowed laminated sand and sandy mud, with all samples being barren of foraminifera. Regression during MIS 4 likely exposed sediment from a shallow marine shoal in cores south of the river, where aeolian forces likely reworked the sand into dunes. Comparing these facies across the Neuse River Basin with similar studies in the region offers valuable insights into how coastal North Carolina's geomorphology responded to changes in relative sea-level during the late Pleistocene.Item Open Access Spatial variation of fracture development during folding of a silty sandstone, West Virginia(East Carolina University, July 2024) Banaszynski, MatthewUnderstanding the evolution of fracture systems in response to progressive folding is crucial for developing structural and hydrogeologic models of these systems. Depending on their specific characteristics, fractures, such as joints and veins can either enhance or detract from permeability within a lithologic layer. Correctly quantifying the specific character such as density of fractures, connectivity, composition, and orientations in geologic media is key to fully understanding subsurface fluid resources. This project aims to add to the discussion on field methodology and findings relevant to fracture characterization by analyzing a sedimentary unit fractured during basin development and folding as a consequence of the Paleozoic Alleghanian orogeny. The Appalachian Basin is a 2000-kilometer long retroarc basin with millions of cubic kilometers of Paleozoic sediment stored in the geologic record. At the westernmost extent of major regional Alleghanian-age deformation in the basin, the structural setting provides an opportunity to investigate how mechanical strength and regional stresses interact to form fractures in sedimentary strata. Deformation of the Chemung Formation, an Upper Devonian mixed siliciclastic unit, was investigated over a 40 km cross section across westernmost Maryland and northeastern West Virginia. The cross section extends through variably folded Paleozoic strata across three fault-bounded structural domains. In total, measurements were taken at 27 individual locations for fractures, lithologic properties, in-situ mechanical strength, and bedding thickness. Additionally, 8 stations were selected for thin section study. All fractures observed in the field were quantified and described using a rapid orientation measurement method which allows for simultaneous collection of quantity and orientation data for a specific bedding unit. In the field measurements of layer mechanical strength were taken using a Schmidt hammer. Stratigraphic data collection included bedding orientation, layer thickness, and qualitative analysis of local folding. Fracture density was later calculated by determining the number of fractures (joints) per square meter of measured beds. The directionality and intensity of Alleghanian folding strongly influences the specific fracture populations present across the study area. The main structural zones studied are, with increasing strain, the Allegheny Plateau, Broadtop Synclinorium, and the Wills Mountain Anticlinorium. The structural zones are separated by significant, kilometer-scale fault and fold systems. Throughout the study area, higher intensity folding generally results in higher fracture density and more strongly clustered joint orientations compared to a relatively low-strain control zone selected for this study. This study further supports previous workers’ conclusions that mechanical layer thickness and structural setting are key controls on fracture density. Across the Chemung Formation, joint densities ranged from 5 to 50 per square meter. In general, joint and vein density increases to the southeast- consistent with regional strain studies- toward the core of the fold and thrust belt, although outcrop observations suggest the Wills Mountain Anticlinorium, the most inboard manifestation of orogenic forcing has been more heavily fractured than the passively folded Broadtop Anticlinorium to the southeast. As folding increases, joint orientations become more strongly controlled by the orientation of the regional scale fold axes. This study also found that meter and smaller-scale folds had minimal impact on local fracture characteristics.Item Open Access Constraints on subvolcanic magma plumbing system evolution from crystal size distribution analysis of igneous groundmass, Henry Mountains, Utah(East Carolina University, July 2024) Johnson, Tess OldroydShallow magma systems drive surface volcanism and are commonly built through multiple injections of magma. Recognizing separate magma injections can be difficult because differences in resulting rock texture, geochemistry, etc. may be subtle or non-existent. However, differences in injection crystallization histories may be recognizable through analysis of the late-crystallizing groundmass in porphyritic subvolcanic igneous rocks. In igneous bodies built from component magma sheets, early injections generally cool rapidly relative to later injections, resulting in distinct groundmass crystal size distribution (CSD) in the youngest, slowly cooled magma sheets compared to older, faster-cooled sheets. Previous work demonstrates that the ~28 Ma Copper Ridge laccolith (Henry Mountains, Utah) was constructed at a depth of ~2 km from at least two texturally distinct igneous sheets stacked atop one another and suggests these two sheets may themselves include multiple injections of magma. This study tests the hypothesis that the relative timing between intrusive sheets in a laccolith can be constrained using CSD analysis of groundmass texture and that the individual intrusive sheets are comprised of multiple pulses of magma. To test this, a suite of porphyritic diorite samples was collected from a natural cross-section through the entire 400-m-thick Copper Ridge intrusion, including samples at well-exposed upper and lower contacts of the laccolith with sedimentary host rock, at contacts with an intercalated layer of host rock within the laccolith, and at regular intervals within the upper and lower igneous sheets themselves. CSD analysis was conducted on electron backscattered diffraction (EBSD) mineral phase maps of quartz, anorthite, and orthoclase in the groundmass (crystals <100 microns). Examining the crystal size population density variation across different elevations of the Copper Ridge Laccolith (CRL) reveals that samples at some elevations have a wider variation of population density with fewer large groundmass crystals, suggesting more rapid crystallization of those samples. The pattern of CSDs at the margins of both upper and lower sheets displays a wider population density variation, suggesting fewer large groundmass crystals and therefore more rapid crystallization at the margins. Additionally, areas within the lower sheet of the CRL at elevations of 2475 and 2575 m exhibit a wider variation of population densities, suggesting more rapid crystallization at these elevations. These regions of fewer large groundmass crystals are interpreted as boundaries between component sheets within the intrusion. Based on these findings, boundaries are interpreted at the top and bottom of both upper (2730 m and 2660 m) and lower (2640 m and 2410 m) sheets. Therefore, the lower sheet is interpreted to contain three component sheets, with boundaries at 2575 m and 2475 m. Overall, the pattern of CSD for the ~100 m thick upper sheet is consistent with injection of a single magma pulse and shows generally larger groundmass crystals suggesting it cooled relatively slowly and perhaps intruded after the lower sheet. The pattern of CSD for the ~300 m thick lower sheet is more complex and shows a wider variation of crystal sizes but has generally fewer large groundmass crystals, suggesting it was intruded before the upper sheet and is constructed from three or more component pulses of magma, each being approximately 100 m thick. The results of this study provide insight into the construction history of the CRL, suggesting that it was constructed through multiple pulses of magma, resulting in distinct CSD patterns for the upper and lower sheets. This has broader implications for understanding the construction history of this and other shallow magma systems, where recognizing multiple magma injections through CSD analysis can offer valuable information on the timing and dynamics of intrusive events. Overall, this study demonstrates the utility of CSD analysis of igneous groundmass in understanding the complex history of shallow magma plumbing systems and provides a framework for identifying and interpreting multiple pulses of magma within igneous intrusions. These findings contribute to a broader understanding of dynamics of shallow magma systems and the processes that drive surface volcanism.Item Restricted Clay mineralogy and geochemistry of Holocene sediments of the Albemarle Sound Estuarine System, North Carolina(East Carolina University) Wyrick, Robert A.Item Restricted Petrology of the Little Valley Formation (Upper Mississippian), Tazewell County, Virginia(East Carolina University) Whitfield, Clifton W.Item Restricted Sedimentation of organic-rich mud in the Neuse River Estuarine System, North Carolina(East Carolina University) Yeates, Douglas D.Item Restricted Hydrogeologic study of the Castle Hayne aquifer system in northern Beaufort County, North Carolina :verification of well field design(East Carolina University) Warner, Debbie.Item Restricted The influence of agriculture on groundwater quality :a hydrogeological and geochemical perspective(East Carolina University) Williams, Janie B.Item Restricted Hydrogeologic investigation of the fresh water resource potential on Cape Lookout, Cape Lookout National Seashore, North Carolina(East Carolina University) Weston-Friedrichs, Jon Nicholas.Item Restricted The position of the fresh water/saltwater interface in hydrostratigraphic units underlying six counties in northeastern North Carolina(East Carolina University) Volosin, Michelle L.Item Restricted Hydrogeologic evaluation of radon activities in groundwater from the Rocky Mount granite pluton, Rocky Mount, North Carolina(East Carolina University) Tarravechia, Richard J.Item Restricted Holocene inner continental shelf stratigraphy, micropaleontology and paleoenvironmental change off the Outer Banks, North Carolina(East Carolina University) Stanton, Christopher.Item Restricted Water quality characterization of two streams in Greenville, North Carolina(East Carolina University) Stewart, Erin A.Item Restricted Sedimentation and morphology on the outer shelf/upper slope transition, Waipaoa River margin, New Zealand(East Carolina University) Sumners, Benjamin W.Item Restricted Groundwater geochemistry of the Castle Hayne Aquifer in capacity use area no. 1, Northeastern NC(East Carolina University) Sutton, Lynn Carole.Item Restricted Stream channel response to urban land use in the inner coastal plain of North Carolina(East Carolina University) Soban, Jason Randal.Item Restricted Origin and evolutionary history of a back-barrier estuarine system, Onslow Beach, NC(East Carolina University) Sproat, Angela M.Item Open Access The geology of Pelzer Quadrangle, South Carolina(East Carolina University) Sieling, David R.Item Restricted Late Holocene geologic development of Pea Island and Avon-Buxton area, Outer Banks, North Carolina(East Carolina University) Smith, Christopher G.Item Restricted Substrate variability and internal sediments of three Carolina bays, South-Central Coastal Plain, North Carolina(East Carolina University) Saunders, Charles L.