Department of Geosciences
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Browsing Department of Geosciences by Author "Baylor University. Dept. of Geology."
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Item Abundance and character of organic matter in cretaceous rocks of Central Texas.(2010-02-02T19:50:39Z) Clark, Stephen M. (Stephen Matthew), 1983-; Dworkin, Stephen I.; Geology.; Baylor University. Dept. of Geology.One of the basic tenants of organic geochemistry states that significant accumulation of organic matter will not occur in well-oxygenated aqueous environments. Changing abundance of sedimentary organic material, therefore, probably reflects changes in marine and terrestrial conditions on Earth. This study will document the abundance and character of sedimentary organic matter in Cretaceous rocks of Central Texas with the goal of reconstructing the environmental, chemical, and depositional conditions responsible for organic carbon accumulation. Organic carbon content in Central Texas ranges from .2 to over 1.5 weight percent. C/N ratios range from 5 to over 25. The C/N ratios are low in the Grayson and Pearsall formations whereas high C/N ratios are characteristic of the Walnut Clay and Lake Waco formations. Carbon isotope ratios of organic matter range from –28.8 to –22.7‰ (VPDB) with lower values occurring in the middle-Cretaceous. Lastly, most δ¹⁵N values of organic matter hover between 1 to 3‰. Although these data could suggest a terrestrial source, the influence of Cretaceous oceanic anoxic events could be causing a marine signature to appear terrestrial.Item Age, genesis, and archaeological geology of the sandy mantle on the Gulf Coastal Plain of Texas.(2013-05-15) Ahr, Steven Wayne, 1970-; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.Alfisols exhibiting strong textural contrasts between sandy A-E horizons (sandy mantle) and clayey Bt horizons on the Gulf Coastal Plain have invoked debate among pedologists, geologists, and archaeologists about parent material uniformity, the age and origin of the sandy mantle, and the scientific value of buried archaeological sites. This dissertation addresses these issues, as well as climate-related variability in the mass-balance of soil constituents, across a 700-mm mean annual precipitation (MAP) gradient. Five Alfisol pedons located on upland summit settings of the Gulf Coastal Plain of Texas were sampled, described, and analyzed. Depth trends in clay-free particle-size classes and Ti and Zr failed to reveal lithologic discontinuities in each pedon, suggesting that the A-E and Bt horizons are genetically related and the textural contrasts resulted from pedogenic, rather than depositional, processes. Thus, any buried archaeological materials would have moved down the profile under the influence of bioturbation and gravity. Optical dating of the soil profiles illustrates complex age structures. Mixing in the A-E horizons effects apparent OSL ages <10,000 years due to admixture of recently and partially bleached quartz grains. Decreased mixing occurs within Bt horizons, and ages increase systematically with depth. Pedogenic weathering alters 40K, U and Th content and environmental dose rates, with concomitant changes in OSL ages. Apparent maximum age calculations from the probable oldest equivalent dose group in soil parent materials suggest the soils began weathering at least by 90-112 ka, and 40-62 ka, which greatly precedes human entry into North America. Mass-balance trends revealed nearly 100% weathering losses of Ca, Mg, Na, Al, and Fe from the A-E horizons, with redistributions and variable gains in Bt horizons. Elemental flux is positively correlated with net mass flux of fine clay and MAP, likely due to increased weathering-related concentrations of negatively-charged clay particles in higher-MAP soils, which facilitate cation adorption and retention. This has implications for predicting pedogenic response to global climate change and for estimating important soil properties in Alfisol-like paleosols in the geologic record.Item Analysis of calcite-filled faults in carbonate strata, balcones trend near Waco, Texas.(2011-09-14) Secrest, Stephen H.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.Five normal faults exposed in the Lehigh Quarry near Waco, Texas, were analyzed. The mechanical stratigraphy of the quarry ranges from relatively strong chalk to marly chalk to chalky marl to relatively weak marl. Higher clay content yields weaker rock. The dip angle of the normal faults varies with rock strength, with steeper dips across the stronger strata. Carbon stable isotopes in 174 samples indicate that the water from which the calcite precipitated is formation water and not meteoric water, while oxygen isotopes indicate that precipitation of secondary calcite in the fault cores occurred between 48° and 110°C. Mechanical twins in macrospar calcite indicate shear stress slightly more than 5-15 MPa, and deformation temperature of <170°C. The microspar fabric includes thin veinlets of secondary calcite and host lithons of cemented chalk wallrock whose orientation relative to the domain boundaries can be used as a shear-sense indicator.Item The Austin chalk and its petroleum potential : South-Central Texas(2017-10-09) Thornhill, Stephen Alan; Baylor University. Dept. of Geology.The Austin Chalk Formation (Upper Cretaceous) consists of uniformly bedded lithologies throughout south-central Texas. The lithologies found within the subsurface are technically wackestones to mudstones. These general textures may be divided into three specific facies: 1) Chalk Marl facies (1,000-7,500 feet), 2) Micritic Limestone (7,500-12,000 feet), and 3) Black calcarous shale facies (12,000 feet). The Chalk has been divided into four specific mappable units: 1) Lower Atco, 2) Upper Atco, 3) Bruceville Chalk Marl, and 4) Futchins Calk. The thickening trends of three units along with the total Austin Chalk interval suggest a uniform period of deposition during the Upper Cretaceous. The sediments deposited during this period were formed along a carbonate ramp-platform depositional environment. Structuring in south-central Texas is primarily faulting and fracturing trends and the homoclinal dip of Chalk to the southeast. The faulting planes are near vertical (65-70 degrees) and strike NE-SW. Fractures are oriented perpendicular to one another and are positioned NE-SW and NW-SE. Production potential of hydrocarbons within the Austin Chalk is controlled mainly by fracture development. Therefore, zones which intersect highly fractured areas are generally good producing wells. Giddings field and various fields within Gonzales County possess the largest amount of hydrocarbon production throughout the study area. Production is greatest in Lee County -- 27 million barrels (bbls) of oil and 75.5 billion cubic feet (BCF) of gas. The cumulative production along the productive chalk trend decreases in a southwesterly direction. This situation implies that fracture development will also show a decrease in this direction. Future development of the Austin Chalk is controlled by economic conditions. However, the best potential zones for future drilling sites may be indicated by "sweet spots" located on cumulative production maps.Item Charcoal chemistry : developing a proxy for paleofire regimes.(2013-09-16) Von Bargen, Justin M.; Hockaday, William C., 1979-; Geology.; Baylor University. Dept. of Geology.Wildfires have occurred over geologic time since the evolution of land plants and affect global biogeochemical cycling and ecosystem processes. Charcoal particles in the geological record may contain information on several aspects of paleowildfire regimes. The fire intensity, the energy produced during a fire, is poorly understood for fires that occurred in the past. I propose that the organic chemical composition of charcoal may be used to approximate the fire temperature. To test this, I used 13C nuclear magnetic resonance (NMR) to quantify the carbon bonding environments in charcoal particles derived from specimens burned during a prescribed fire at the Lake Waco Wetland in Waco, Texas. I compared the NMR data for charcoal to fire temperatures measured by thermocouples and was able to predict the temperature within 89°C. The intrinsic relationship between pyrolysis temperature and charcoal structure may allow for a better understanding of past conditions during fires.Item Climatic and human influences on Holocene alluvial history and paleoenvironment of the middle Delaware River Valley, USA.(2012-11-29) Stinchcomb, Gary E.; Driese, Steven G.; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.The potential for future prolonged drought episodes in the Northeastern USA is alarming given that a humid climate currently provides water to +50 million people in the northeast, USA. Hydro-climatic projections are hampered by a lack of regionally-based paleoenvironmental reconstructions. The middle Delaware River Valley provides a unique opportunity to expand the Holocene alluvial history and paleoenvironment for the northeast, USA. Thirty-six soil profile descriptions, 332 grain size analyses, and 82 14C ages from trenches and auger borings show that similar alluvial landforms within the river valley have different formation histories and depict a valley that has experienced middle to late Holocene floodplain and terrace reworking. Despite erosion, secular changes in buried soil and sediment properties are closely associated with climate change and land-use. A Holocene time-series was constructed using 149 δ13Csom values from alluvial terrace profiles. There is good agreement between increasing δ13Csom and Panicoideae phytolith concentrations, suggesting that variations in C4 biomass are a contributor to changes in the soil δ13C. A measurement error deconvolution curve over time reveals two isotope stages (II and I), with nine sub-stages exhibiting variations in average δ13Csom (%C4). Stage II, ~10.7-4.3 ka, shows above average δ13Csom (increase %C4) values with evidence of an early Holocene warm/dry interval (sub-stage IIb, 9.8-8.3 ka) that coincides with rapid warming and cool/dry abrupt climate change. Sub-stage IId, 7.0-4.3 ka, is an above average δ13Csom (increase %C4) interval associated with the mid-Holocene warm/dry Hypsithermal. The Stage II-I shift at 4.3 ka documents a transition toward below average δ13Csom (decrease %C4) values, coinciding with decreasing insolation and moisture budget reorganization. Sub-stages Ib and Id (above average %C4) coincide with the first documented occurrence of maize in northeastern USA and population increase during the Late Woodland. These associations suggest that humans influenced δ13Csom during the late Holocene. The influence of land-use is further corroborated by a regionally extensive anthropogenic sedimentation event documented throughout eastern North America, pre-Colonial sediment (PCS) circa: A.D. 1,100–1,600. These data demonstrate that combined prehistoric land-use and climate change impacted eastern North American floodplains several hundred years prior to the onset of European Settlement.Item A comparison of the Cretaceous (Albian) Edwards Limestone bioherms of Central Texas with the Holocene Coral Reefs of Bermuda.(2011-09-14) Damman, Adam J.; Bonem, Rena Mae.; Geology.; Baylor University. Dept. of Geology.The Edwards Limestone of Central Texas is comprised of numerous rudist-dominated patch reefs that are collectively referred to as the Central Texas Reef Trend. These bioherms were protected by the Stuart City barrier reefs along the Texas Gulf Coast. The Stuart City reefs have been compared with the modern barrier reefs of Australia and Belize, but there is currently no modern analog for the Central Texas bioherms. Bermuda was chosen for a modern analog study based on the existence of a protective rim reef system, its low biodiversity, and a slower reef growth rate as compared with other modern reefs. Although the patch reefs of Bermuda were determined to be “similar” to the Central Texas Edwards Limestone bioherms in many respects, the high temperatures and unique oceanographic conditions of the Cretaceous likely means that no exact modern analog for the rudist-dominated Edwards bioherms exists.Item Controls on reservoir continuity and distribution within the Mississippian Pekisko Formation at Twining field, south-central Alberta, Canada.(2007-02-06T23:10:25Z) Josson, Erika M.; Atchley, Stacy C.; Geology.; Baylor University. Dept. of Geology.Twining field, located in south-central Alberta, Canada, and discovered in 1951, produces from the Mississippian Rundle Group. Estimates of original in-place oil are 913 million barrels, with 46 million barrels identified by the Alberta Energy Utilities Board as recoverable (5% recovery factor). Cumulative production to date from the Rundle Group at Twining is 31 million barrels (67% of recoverable reserves). The Pekisko Formation of the Rundle Group is a carbonate reservoir that is unconformably overlain by the Lower Cretaceous Mannville Group. Reservoir quality (porosity and permeability) is best developed in the shoal facies association contained within 9 shallowing-upward parasequence sets that are relatively continuous across the study area where they are not karst-modified or truncated beneath the basal Cretaceous unconformity.Item Controls on the accumulation of organic matter in the Eagle Ford Group, Central Texas, USA.(2014-01-28) Boling, Kenneth S.; Dworkin, Stephen I.; Geology.; Baylor University. Dept. of Geology.The Upper Cretaceous Eagle Ford Formation is an organic rich marine mudrock which outcrops across central Texas. This study documents the chemostratigraphic character of the Pepper and Eagle Ford Formations in central Texas using major and trace elements, organic matter abundance, and the isotopic and stoichiometric character of organic matter. The chemical data allow the identification of six distinct chemofacies that are potentially useful for correlation purposes. Based on these data, changing paleoceanographic conditions were documented ranging from normal marine conditions associated with the Pepper Formation, anoxic conditions associated with the Lower Eagle Ford Formation, suboxic conditions associated with most of the upper Eagle Fords, and then a return to normal marine conditions at the top of the Eagle Ford Formation. The high TOC content of the lower Eagle Ford was most likely caused by high productivity which in turn drove conditions to anoxia.Item Correlation of earthquakes with seismogenic faults along the Northern Arizona Seismic Belt, southwestern margin of the Colorado Plateau.(2011-09-14) Lancaster, Daniel S.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.The Northern Arizona Seismic Belt (NASB) is one of the most seismically active areas in Arizona, and extends from near Kanab in southernmost Utah to the Mogollon Plateau south of Flagstaff, Arizona. The NASB defines the seismic boundary between the Colorado Plateau and the Basin and Range Provinces. This research attempts to spatially correlate four M≥4.0 earthquakes that had epicenters in the Kanab-Fredonia area of the NASB with the faults that might have generated them. Earthquakes were correlated spatially with mapped faults and distinct geomorphic lineaments within the West Kaibab fault system, which to the point has minimal documented evidence of late Neogene movement. Recognition of recent seismicity along the West Kaibab fault system is consistent with the hypothesis that Basin and Range extensional faulting is expanding into the Colorado Plateau.Item The county bias of severe thunderstorm warnings and severe thunderstorm weather reports for the Central Texas region.(2008-06-09T15:17:52Z) Barrett, Kevin M.; Greene, Donald Miller, 1949-; Geology.; Baylor University. Dept. of Geology.Severe thunderstorm warnings issued by the National Weather Service and severe thunderstorm weather reports dating from January 1, 1986 to December 31, 2005 were analyzed to find a potential county bias in the issuance of severe thunderstorm warnings. Choropleth maps and statistical analysis of the data reveal a population density bias for both severe weather reports and severe thunderstorm warnings issued as well as a likely distance bias. Additional non-meteorological county warning and severe weather report biases were found for several counties in the study area that may relate to socioeconomic factors, physiographic influences and county size and directional orientation. Proximity to interstate highways also appears to have an effect on the reporting of severe weather events and the issuance of severe thunderstorm warnings.Item Depositional and diagenetic controls on reservoir quality and their petrophysical predictors within the Upper Cretaceous (Cenomanian) Doe Creek Member of the Kaskapau Formation at Valhalla Field, Northwest Alberta.(2009-04-03T12:43:53Z) Ball, Nathaniel H.; Atchley, Stacy C.; Geology.; Baylor University. Dept. of Geology.Valhalla Field, discovered in 1979 and located in northwest Alberta, produces from the Upper Cretaceous Doe Creek Member of the Kaskapau Formation. Original reserves in place are 44 x 106m3 of oil, of which 10.3 x 106m3 of oil (82% of recoverable reserves) have been produced (ERCB, 2008). This study evaluates the depositional and diagenetic controls on reservoir quality within the Doe Creek at Valhalla Field in order to identify reservoir-prone facies and predict their distribution in wells lacking core. Analysis of core and well log data indicates that intervals of highest reservoir quality are preferentially associated with thin (meter-scale) sandstone bodies deposited in proximal lower and upper shoreface environments. Based upon the relationships of facies to deep resistivity, mud content as gamma-ray derived shale volume, and density-neutron porosity separation within cemented zones, a well log transform was created that successfully predicts the distribution of reservoir-prone facies and calcite cement.Item Detailed paleoclimatic records from late Pennsylvanian polygenetic paleosols : north-central Texas, USA.(2013-09-24) Culbertson, Amos.; Driese, Steven G.; Geology.; Baylor University. Dept. of Geology.Two Canyon Group (late-Pennsylvanian, Missourian) multistory, polygenetic paleosol intervals in north-central Texas, USA record complex paleoclimatic and paleohydrologic histories. Both paleosol intervals show evidence for initial development under well-drained conditions (illuviated clay, pedogenic calcite nodules, high-chroma matrix colors) and are overprinted by features that indicate poorer drained conditions (gley matrix colors, pedogenic siderite), however overprinting occurred through rapid transgression in one paleosol and gradual sea-level rise in the other. Reconstructed physical and wet chemical soil properties indicate these paleosols were finely textured, fertile, and void of salinity problems. Paleoatmospheric pCO₂ estimates from the δ¹³C values of pedogenic calcite nodules indicate values near pre-industrial levels (360ppmV), which are in agreement with previously published proxy and modeling results. This study shows that despite multiple episodes of overprinting, a detailed paleoclimatic and paleohydrologic history can be reconstructed from paleosols using careful macro and micromorphological observations.Item Developing a geospatial model for analysis of a dynamic, heterogeneous aquifer : the Brazos River Alluvium aquifer, Central Texas.(2012-08-08) Wong, Stephanie S., 1984-; Yelderman, Joe C.; Geology.; Baylor University. Dept. of Geology.The Brazos River Alluvium aquifer extends from Bosque County to Fort Bend County and is one of 21 minor aquifers in Texas. In the past, this aquifer has mainly served as a source of irrigation water. However, increasing demands for water, especially in the Waco area, has renewed interest in this under-utilized source of shallow groundwater. Shallow, unconfined aquifers such as the Brazos River Alluvium aquifer present unique management challenges due to their lithologic heterogeneity, fluctuating saturated thickness, and proximity to surface sources of contamination. In this study, a geospatial approach was used to compile and analyze various datasets to model aquifer thickness and available water in the northern reach of the Brazos River Alluvium aquifer.Item Effects of surface heterogeneity on the colloidal stability, protein adsorption and bacterial interaction of nanoparticles.(2014-01-28) Huang, Rixiang; Lau, Boris L. T.; Geology.; Baylor University. Dept. of Geology.Interfacial processes like aggregation and deposition control the transport and fate of natural and engineering nanoparticles (NPs) in the environment, which are relevant to important environmental processes, applications, and effects of NPs. These processes are controlled by a wide range of NP properties. Depending on the time frame and nature of the interfacial processes, a combination of different techniques (including dynamic light scattering, isothermal titration calorimetry, batch adsorption and spectroscopic techniques) were used to systematically investigate the effects of surface heterogeneity on the colloidal stability, protein adsorption and bacterial interaction of self-assembled monolayer coated gold nanoparticles (AuNPs). These AuNPs have similar size and shape but quantitative difference in the ligand composition and distribution on their surface, therefore serve as ideal models for heterogeneous surfaces that are ubiquitous in the environment and engineering system. Key findings of this work include: 1) In addition to surface chemical composition, the organization of different functional groups on NP surface was also found to influence the electrical double layer structure and the relative contribution of different interfacial forces. Therefore, direct comparison of zeta potential of different particles and the prediction using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory should be made with cautions; 2) The effects of surface heterogeneity were found to be scale-dependent in NP-protein interactions. The size of proteins and surface features of NPs together determined the interaction mechanism (e.g., binding stoichoimetry and forces involved). The interaction mechanism subsequently affects the protein corona structure; 3) When these AuNPs adsorb onto bacterial cells, the adsorption kinetics is in agreement with the DLVO prediction, where the magnitude of electrostatic repulsion determines the diffusion of NPs onto bacterial cell. The adsorption capacity reflects the influence of surface heterogeneity on the association of bacterial surface components with these AuNPs. Overall, these findings improve our understanding on the effects of surface heterogeneity on representative interfacial processes that control the transport and fate of NPs. This work also provided new insights into better design of surfaces for various applications.Item Electrical resistivity imaging for characterizing dynamic hydrologic systems.(2008-10-01T15:35:15Z) Amidu, Sikiru Adetona.; Dunbar, John A., 1955-; Geology.; Baylor University. Dept. of Geology.Electrical resistivity imaging (ERI) is widely used in hydrogeophysical studies for monitoring spatiotemporal variations in hydrologic properties and processes. Its applications to hydrologic settings found in sandy and other coarse-grained soils have been demonstrated. However, there has been limited use of the method for characterization of dynamic hydrologic systems such as those found in Vertisols (typical heavy-clay soils) and water layers in lakes. One reason for this is that principles that work well in sandy and loamy soils often produce erroneous results in clay soils. In addition, because of the dynamic nature of such systems, detailed empirical and computational studies are required to fully understand various properties, which vary spatially within a few meters or less, and temporally in less than few days. This dissertation investigates the effectiveness of ERI for characterizing dynamic hydrologic systems. Two specific questions are addressed: 1) Can spatiotemporal hydrologic variations in such systems be effectively characterized using ERI? 2) How accurately can the true resistivity distribution in the systems be determined? To address the first question, geoelectric studies of seasonal wetting and drying of a Texas Vertisol were carried out. Data processing involved inversion, temperature corrections and time-lapse analysis. In addition, a van Genuchten water retention function was incorporated into the study to estimate moisture flux. To answer the second question, theoretical and field geoelectric data from Lake Whitney, Texas, USA, were analyzed. Following an introduction to the research in chapter one, results of geoelectric studies of seasonal wetting and drying of the Texas Vertisol are presented in chapter two. Results reveal the seasonal hydrodynamics of the soil as they are controlled by micro-relief topography (gilgai) and cracks. In chapter three, time-lapse analysis and computations of the apparent moisture flux are discussed. This study shows that integrative hydrogeophysical and hydropedological method is a viable approach for visualizing moisture flux in soils. In chapter four, results of geoelectric studies in Lake Whitney are discussed with recommendations for advancing the ERI as a tool in limnological research for mapping freshwater zones within impacted lakes and water reservoirs. Chapter five presents brief summary and conclusion of the research.Item Fluvial sequence stratigraphy and paleoclimate of the Upper Triassic (Norian-Rhaetian) Chinle Strata, northern New Mexico.(Tulsa, OK : Society for Sedimentary Geology., 2007-11) Cleveland, David M.; Atchley, Stacy C.; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.Two age-equivalent Upper Triassic (Norian and Rhaetian) fluvial successions in New Mexico were evaluated from a sequence-stratigraphic and paleopedologic perspective. Meter-scale fining-upward fluvial aggradation cycles (FACs) comprise fluvial aggradational cycle sets (FACSETs) 4-15 m thick. FACSETs in turn stack into four fluvial sequences 26-48 m thick. Fluvial sequences correlate between the two locations and likely accumulated in response to pulses of source area uplift and/or basin subsidence. Conversely, higher-frequency FACs and FACSETs that occur within sequences do not correlate between study areas and are likely the products of autocyclic processes, such as channel avulsion, floodplain aggradation, and channel migration. These results suggest that regionally significant tectonic episodes may be discernible in suspended-load fluvial deposits that accumulated over a broad area. Each location contains abundant paleosols of varying maturity with relatively consistent features throughout the strata. A typical paleosol profile has features similar to modern Aridisols, is about 1 meter thick, and has an AB–Bw–Bk–BC horizon succession. Depth-to-carbonate functions estimate that mean annual precipitation was between 200 and 450 +/-95 mm. Root traces in the paleosols are typically shorter than a meter and less than a centimeter wide. By comparing these paleosols to climate-sensitive characteristics of modern soils, this study demonstrates that the Late Triassic Western Interior during the Late Norian to Rhaetian was arid to semiarid and supported a desert shrub environment that had localized and periodic moist or saturated soil conditions. Quantitative isotopic climate proxies are applied to the isotopic composition of pedogenic carbonates in order to construct two age-equivalent, relatively continuous pCO2 and temperature records that span the eight million years preceding the Triassic-Jurassic (T-J) boundary. The [delta]13C data reveal relatively low Late Norian pCO2 levels (<500 to 1,000 ppmV), increased Rhaetian levels (>1,500 ppmV), and at least two periods of extreme pCO2 levels (~3,000 ppmV) preceding the T-J boundary. [delta]18O data from the same time interval suggest that mean annual temperatures (MAT) increased by 7 - 9 [degrees] C in association with the peak increases of pCO2 levels. The T-J boundary is associated with widespread marine and terrestrial extinctions, and it is possible that climate was a significant driving mechanism of the Late Triassic biotic crisis.Item Geochemical fingerprinting of sediments on the Pear Tree Bottom Reef, near Runaway Bay, Jamaica.(2009-04-01T17:22:06Z) Westfield, Isaac T.; Dworkin, Stephen I.; Geology.; Baylor University. Dept. of Geology.Pear Tree Bottom Reef, near Runaway Bay, Jamaica, was originally described by T. F. Goreau in the 1950‟s and is noted for its "Buttress Zone" morphology and presence of sclerosponges at water depths less than 30m. Since 2005, increased sedimentation has caused a drastic decline in reef health. It is thought that this increased sedimentation is related to two concurrent construction projects: the reconstruction of the north Jamaican costal highway and construction of the Gran Bahia Principe Resort along the coast adjacent to the reef. The Falmouth Limestone (~125ka), the Hopegate Limestone (~250ka), and the Montpelier Limestone (~1.9ma) all occur within the PTB River drainage basin. Reef sediment, limestone, and soils samples were analyzed for particle size, insoluble residue, mineralogy, and elemental chemistry to ascertain the source of the increased sedimentation on the PTB Reef. An ecological survey at Pear Tree Bottom indicated a drop in coral to algae ratios and therefore a decline in overall reef health. Laser particle size analysis, x-ray diffraction, ICP-MS, and ICP-ES all indicate an increase in detrital sediment on the reefs from west to the east as well as a significant increase at Pear Tree Bottom that is likely a result of the resort construction.Item Geology of the Late Pleistocene artifact-bearing Wasiriya Beds at the Nyamita locality, Rusinga Island, Kenya.(2011-12-19) Van Plantinga, Alexander A.; Peppe, Daniel J.; Geology.; Baylor University. Dept. of Geology.This study investigated the sedimentology and stratigraphy of the Late Pleistocene Wasiriya Beds at the Nyamita locality on Rusinga Island, Kenya in northeastern Lake Victoria. Little is yet known about this region during the Pleistocene. This study provides geological context for archaeological research of the stone artifacts in the Wasiriya Beds, for the paleontological work on the fauna of these beds, and for other paleoenvironmental research in these beds. A robust tephrostratigraphic framework was established using diverse statistical methods. Radiocarbon dates confirm a Late Pleistocene age for these deposits. A valley-drainage model was integrated with a facies model to infer their paleoenvironmental history. Sediments suggest a generally sharply alternating wet and dry seasonality. Geological evidence does not suggest that the Lake Victoria region was especially arid just prior to the Last Glacial Maximum. Additional data from the lower Wasiriya Beds could elaborate on their paleoenvironmental significance.Item Impacts of estimating recharge on groundwater modeling for arid basins.(2006-05-28T23:51:44Z) Huffman, Janelle H.; Yelderman, Joe C.; Geology.; Baylor University. Dept. of Geology.Quantifying recharge and spatially identifying recharge distribution is important for evaluating groundwater sustainability, especially in arid regions. A Guelph Permeameter helped identify specific recharge areas and the Soil Water Assessment Tool (SWAT) provided meaningful recharge rates used for modeling Wild Horse Basin in southwest Texas. SWAT generated recharge values that were subsequently used in two transient MODFLOW simulations: one with the recharge distributed according to sediment unit location (distributed zonation), and one with the recharge concentrated in cells adjacent to the mountain fronts surrounding the basin (mountain-front zonation). When comparing the model results to historic well hydrographs, mountain-front recharge appeared to improve calibration. A deterministic analytical model like SWAT is helpful in estimating recharge in arid basins and can create meaningful input parameters for numerical models like MODFLOW. MODFLOW was in turn able to evaluate SWAT recharge estimations for Wild Horse Basin using calibration and sensitivity analyses.
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