Department of Geosciences

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Lithostratigraphic and depositional framework, near-surface Upper Pennsylvanian and Lower Permian strata, southern Brazos Valley, North-central Texas.
(1965) Seals, Mary J.
The purpose of this study was to interpret the depositional framework of the original Cisco Group, Upper Pennsylvanian and Lower Permian, in the shallow subsurface of North-central Texas, Stratigraphic interpretation was based on several subsurface mapping methods—(1) stratigraphic cross sections, (2) isopach maps of limestone-bounded intervals, (3) sandstone percentage maps, (4) structure contour maps, (5) channel sandstone isopach maps, (6) paleotopographic maps, (7) well sample study, and (8) various special maps and cross sections. Several classifications of the Upper Pennsylvanian and Lower Permian strata have been proposed; however, Plummer and Moore's (1922) classification, although not completely suitable, applies best to the study interval. The problem of the Pennsylvanian-Permian boundary was not a concern of this study. The strata of the Cisco Group in the study area consist, in order of abundance, of shale, sandstone, limestone, and coal. Rock characteristics and interpretation of depositional environments was of necessity based primarily on electrical responses and geometric distribution. Little is known about shales within the study area except that they may be highly fossiliferous, commonly carbonaceous, and probably represent transitional environments. Relatively thin, widespread limestones persist throughout the study interval and represent decrease in clastic influx. The persistent limestones are important in subsurface correlation. Sandstone deposits can be divided into sheet sandstones of probable marine origin and linear channel-fill sandstone bodies. Topographic and structural lows were apparently controlled to some degree by differential sand-shale compaction and by compaction of shales underlying massive sandstone bodies. These local compactional features are superimposed on a broad, regional monocline. Interpretation of channel trend relationships to structure and underlying strata has been an important aspect of this investigation. The dominant orientation of channel trends is in a west-southwest direction, which probably reflects a source area to the east and northeast of the study area. Channels are best developed in structural lows which apparently were also paleotopographic lows. In non-channel areas differential shale compaction created topographic lows on which a succeeding channel would probably develop. Subsidence due to shale compaction beneath massive sandstone bodies also created topographic lows, which are commonly areas where an upper channel crosses a lower channel. As many as five intersections were observed in a local area. Continued surface and subsurface research is necessary to describe sufficiently the depositional history of the Cisco Group of North-central Texas. Suggestions for further study include (1) extension of the study downdip and along strike, (2) more dense well control on a larger map scale, (3) mineralogic, petrologic and sedimentary structure studies, and (4) paleotopographic surface and subsurface studies.
Subsurface Stratigraphy of the Strawn and Canyon Groups of west central Texas, Concho and Menard counties
(1983) Woodard, Jan N.; Grayson, Robert; Parker, Don; Baylor University.
Carbonate rock units of the upper Strawn Group (Desmoinesian) developed on the western flanks of the Llano uplift on a positive topographic platform, the Concho shelf. Late Mississippian and early Pennsylvanian orogenic uplifts along the Texas craton exposed the Ordovician Ellenburger Group carbonate rocks to extensive erosion and provided the paleotopographic unconformity upon which these cyclic limestones and shales were distributed. Orogenic activity related to the advancing Ouachita Fold Belt occurred synchronously with late Strawn deposition. The rising Ouachita orogenic belt initiated a fluvial-deltaic depositional complex that prograded over a slowly subsiding carbonate shelf. In early Canyon time (Missourian) deformation along the Ouachita Fold Belt decreased in intensity and a more stable carbonate platform environment was reestablished on the shelf. Cycles of marine and prodeltaic shales capped by algal limestones characterize the Canyon Group. Paleotopographic variations in the lower Canyon indicate early Missourian tectonic movement in the Ellenburger limestones. In contrast, the wedge-shape geometry of the upper Canyon carbonate units suggest shoreward-building carbonate banks. These banks developed over very porous, water-saturated prodelta shales and gained thickness as accumulating carbonates compressed the unconsolidated distal muds.
Environmental framework, structural evolution and petroleum potential of the Cambrian Wilberns Formation West-Central Texas
(1984) Poorman, Stephen Eugene; Beaver, Harold; Baylor University.
The Wilberns Formation (Upper Cambrian) in the subsurface of west-central Texas is composed predominantly of sandstone units. Subsurface mapping of the Wilberns shows the sandstones to be persistent throughout most of the study area. Analyses of core samples indicate that the upper portion of the Wilberns Formation consists of a lower sandstone facies overlain by a dolomitic interval. The suite of sedimentary structures present in both facies suggests tidal flat deposition and the electric log signatures are similar to those produced by channel and tidal sand bodies. Thus, it is postulated that the Wilberns Formation was deposed on extensive tidal flats in tidal channels. The Fort Chadbourne fault system is a linear zone of deformation trending from Sutton County northward into northeastern Nolan County. This structural zone has uplifted and faulted the Wilberns Formation. The presence of en echelon faults and folds as the predominant structures along the Fort Chadbourne system suggests wrench faulting. The orientation of the faults (N-S) and folds (NE-SW) suggests that the wrench system had left lateral movement produced from compressive forces active during the Ouachita orogeny. Thin section analyses of core samples produced a general paragenetic sequence for the upper sandstone units of the Wilberns Formation consisting of at least four diagenetic stages as follows: (1) Burial and compaction leading to reduction of primary porosity and development of quartz overgrowths. (2) Precipitation of dolomite cement into remaining pore space. (3) Uplift and exposure leading to dissolution of calcareous materials, resulting in development of secondary porosity. (4) Re-burial and precipitation of hematite, pyrite and clays as pore lining and pore fill. Hydrocarbon migration probably occurred during this stage. This sequence of diagenetic events is responsible for the excellent reservoir quality of the sandstone units within the Wilberns Formation; it is found only along the Ford Chadbourne fault system.
Hydrogeologic assessment of shallow groundwater flow systems in the Walnut Formation, Central Texas
(1994) Feckley, David Lee; Baylor University.
The Walnut Formation is the most clay-rich member of the limestone dominated Lower Cretaceous rocks of central Texas. Due to this clayey nature, the Walnut Formation is a natural target for landfills in this region. Shallow groundwater flow systems present within the Walnut Formation provide baseflow to streams which transect the Walnut outcrop belt in Central Texas. Three sites within the outcrop belt of the Walnut Formation were investigated. The Walnut flow systems are geomorphically and stratigraphically controlled, and recharge zones are influenced by the geomorphic history and subsequent soil formation. Discharge zones are controlled by seasonal influences, stratigraphy, and geomorphic position. Field observations indicated saturated zones in the near surface Walnut Formation may produce hydraulic heads above ground elevation. These saturated zones, within the weathered depth of the Walnut Formation, discharge to main streams by tributary discharge and spring flow. Conceptual models of the flow systems were constructed following field observations, hydrogeolgic testing (slug tests and pumping tests), geochemical analyses, and hydrograph analysis and interpretation. Regionally, the Walnut flow systems relate to the condition of the underlying Paluxy Formation (a minor aquifer). Flow systems of the Walnut Formation are important from a regional perspective due to the potential of non-point source contamination to surface waters by landuse practices on the Walnut outcrop area.
Paleoenvironmental Variability across the Cretaceous-Tertiary Boundary in the Alberta Foreland Basin, as Interpreted from Fluvial Deposits and Paleosols, Red Deer River Valley, Alberta, Canada
(2002) Forkner, Robert Murchison; Nordt, Lee C.; Baylor University.
The integration of sedimentological, paleotectonic and paleopedogenic data across the Cretaceous-Tertiary (KT) boundary of south-central Alberta indicates fluvial aggradation and variability of paleosol morphology in response to foreland orogenesis. The depositional history records an evolution from amalgamated, multi-story, braided sand bodies to accretionary, single-story, overbank-prone meandering deposits. The distribution of paleosols throughout the section is also cyclic. Immature, well-drained paleosols are associated with the braided deposits, whereas mature, poorly-drained paleosols are interbedded with the meandering deposits. Two large-scale aggradational fluvial cycles are observed within the study interval and are interpreted to record variations in sediment supply and tilt of the depositional profile associated with foreland tectonism. Orogenic pulses are reflected in outcrop by amalgamated fluvial deposits interbedded with immature paleosols. Waning orogenesis is characterized by reduced fluvial sedimentation rates and an increase in the number of mature paleosols. Orogenic quiescence is associated with an increase in channel sinuosity, and poorly drained, gleyed, coal-capped paleosols. The KT boundary is located three meters above the tectono-stratigraphic transition from amalgamated, braided fluvial systems with well-drained paleosols to accretionary, meandering fluvial systems with poorly-drained paleosols. A gradual shift towards a more poorly-drained paleosol morphologies and increasingly accretionary fluvial styles suggests that the KT event was not the cause of increasingly cool and wet conditions across the boundary, but that the boundary lies at the inflection point between a well-drained to poorly-drained depositional cycle.
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.
The sequence stratigraphic evolution of the Sturgeon Lake bank, central Alberta, Canada and its regional implications.
(2006-05-29) Kahmann-Robinson, Julia A.; Atchley, Stacy C.; Geology.; Baylor University. Dept. of Geology.
Sturgeon Lake South (SLS) is an isolated Devonian (Late Frasnian) platform located within the Western Canada Sedimentary Basin (WCSB). Stratigraphic correlation of the Leduc Formation across the WCSB reveals a dominantly backstepping stratal geometry. The Sturgeon Lake South bank complex is composed of 12 retrogradationally stacked depositional sequences. Sequences 1 and 2 prograde, and sequences 3-6 backstep. Bank formation and stratal geometries are controlled by eustatic sea level fluctuations in concert with: 1) a northeasterly paleowind direction that induced highly aggradational windward margins, 2) antecedent topographic highs (e.g., Peace River Arch) that induced progradational margins and, 3) sediments derived from the Antler Orogeny that increased marine turbidity and influenced the termination of platform growth. Within the Leduc Formation at SLS, dolomitization is pervasive and fabric destructive, enhances reservoir quality, and is not facies specific. Dolomitization most likely occurred within the burial environment.
Paleosols as an indicator of ancient landscapes, climates and stratal response during the Triassic: the Salt Anticline Region of Utah.
(2006-05-29T01:46:53Z) Prochnow, Shane J.; Nordt, Lee C.; Geology.; Baylor University. Dept. of Geology.
Modern soils are excellent indicators of environmental conditions, and paleosols can be used as proxy for past conditions. This dissertation documents the response of Triassic paleosols and fluvial sediment accumulation to 1) landscape dynamics influenced by subsurface salt movement and 2) variations in paleoclimatic conditions in eastern Utah. The first chapter is an introduction to the research. The second chapter examines the influence of salt tectonics on cyclic stratigraphy, paleosol morphology, and sedimentation rates. The distribution of paleosols are documented within a sequence stratigraphic framework to evaluate whether salt tectonics influenced patterns fluvial sediment dispersal. The Chinle Formation is divided into two sequences that are in turn composed of decameter-scale fluvial aggradational cycle sets (FACSET) and meter-scale fluvial aggradational cycles (FAC). Facies and paleosol distributions within this stratigraphic framework suggest that a minibasin initially increased and then decreased in diameter and that the axis of subsidence drifted to the northwest through the Late Triassic. The third chapter documents how ancient slopes, a geomorphic expression of halokinesis, controlled paleosol development through a traditional catena perspective. Paleoslopes on a major sequence boundary that extends across the minibasin control associated paleosol development. Pedotopographic influences included both downslope redistribution of sediment and change in soil hydrology. The fourth and final chapter utilizes a multi-proxy paleosol approach to reconstruct climatic and atmospheric conditions during the deposition of Triassic fluvial sediments and the formation of paleolandscapes associated with halokinesis. Paleoclimate reconstruction supports the occurrence of a global pluvial episode during the Carnian (late Middle Triassic) that contrasted with mostly arid climates during the Middle to Late Triassic. Arid (and near arid) episodes in the latest Moenkopi and upper Chinle contradict monsoonal seasonality, whereas the lower Chinle pluvial suggests a non-continental climate similar to the modern eastern United States. Drastic changes in rainfall and soil types indicate that the Middle to Late Triassic in eastern Utah was an interval of dynamic climate change that may partially be tied global carbon dioxide levels and tectonism.
Structural analysis of the Criner Hills, South-Central Oklahoma.
(2006-07-31) Walker, William M.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.
It has been suggested that there may have been Quaternary displacement along the Criner Hills Fault in South-Central Oklahoma. The Criner Hills Fault is generally on-trend with the active Meers Fault, which has led some to suggest that the Criner Hills Fault may also be active. A GIS database has been created that combines aerial photographs, satellite imagery, published geologic maps, and digital elevation models of the area around the surface trace of the Criner Hills Fault. Subsurface data from ~150 hydrocarbon exploration and production wells were used with the surface data to construct a 3D structural model of the study area, assisted by the structural modeling application LithoTect. The Kirby Fault is interpreted to be a major reverse fault that controls the topography and structure of the Criner Hills. The Criner Hills Fault is interpreted to be an inactive, secondary structure related to the Kirby Fault.
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.
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.
Seismo-lineament analysis of the Malibu Beach quadrangle, Southern California.
(2007-12-04T20:05:30Z) Seidman, Lauren E.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.
The Santa Monica Mountains are a young, structurally active mountain range within southern California. The purpose of this study was to map seismogenic faults within the Malibu Beach quadrangle. Using available earthquake data, I projected fault-plane solutions onto a digital elevation model (DEM). The intersection of each fault-plane solution with the DEM yielded a seismo-lineament whose width reflected the reported confidence interval associated with the earthquake location. Geomorphic lineaments were identified and mapped by illuminating the DEM at a 45 degree elevation from various azimuths. The lineament maps were used to generate hypotheses about the possible location of structures, which were field evaluated. Field work verified the existence of previously unmapped faults along some lineaments. Some faults are approximately coplanar with earthquake fault-plane solutions, and are tentatively considered seismogenic. Focal mechanism solutions and field observations suggest that strain is partitioned between several active faults, including some with pure strike-slip displacements.
Linking onshore and offshore data to find seismogenic faults along the Eastern Malibu coastline.
(2007-12-04T20:06:41Z) Millard, Mark Alan.; Cronin, Vincent S.; Geology.; Baylor University. Dept. of Geology.
The Santa Monica Mountains form part of the structurally active southern edge of the Transverse Ranges Province. The purpose of this research is to identify and characterize potentially seismogenic faults in onshore and offshore portions of the Topanga 7.5’ Quadrangle using near-shore geophysical data, multibeam data, digital elevation models, earthquake focal mechanism solutions, and field work. Several faults, many of which are previously-unmapped, have been identified in the study area, and determined to be potentially seismogenic. Results show that active seismogenic faulting in the Santa Monica Mountains is not restricted to the Malibu Coast Fault Zone as previously hypothesized. The sub-bottom acoustic survey provides evidence for the continuity of the Potrero Canyon and Santa Monica Faults in the nearshore portion of the Santa Monica Bay. Seismo-lineaments projected into the Santa Monica Bay indicate that one or more faults identified in the offshore portion of the study area may be seismogenic.
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.
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.
Modeling channel erosion in cohesive streams of the Blackland Prairie, Texas at the watershed scale.
(2008-10-02T18:43:42Z) Capello, Stephanie V.; Allen, Peter M., 1947-; Geology.; Baylor University. Dept. of Geology.
Stream bank erosion is a product of submerged and subaerial processes. The goal of this research was to assess the application of the submerged jet test to predict erosion of cohesive stream banks in the Blackland Prairie of North Central Texas, an area with over 40% of the State’s population. In situ erosion monitoring was conducted by utilizing erosion pins and water level loggers at seven field sites with contributing drainage areas of 5-239 square kilometers. Erosion pins were placed at two locations on the cutbank wall and monitored over one year. Erosion rates during the monitoring period were a function of bank height and flow duration. Submerged jet test values from samples taken at the same locations as the erosion pins predicted erodibility of the material ranged from 0.0034-0.0065 cm3/N-s. Erosion pins indicated 30.35-572.00 mm of loss. The predicted erosion coefficients from the jet test, tractive force, and cumulative flow duration was within 31% of the field erosion. This study evaluates the first in situ testing of the erodibility of cohesive stream banks with cumulative flow duration, cumulative tractive force, and subaerial processes.
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.
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.
Rise of the Givetian (385 Ma) Forests, Northern Appalachian Basin, Catskill State Park, New York, U.S.A.
(Society for Sedimentary Geology (SEPM), 2010) Mintz, Jason S.; Driese, Steven G.; Geology.; Baylor University. Dept. of Geology.
Forestation on Earth may have profoundly changed fluvial sedimentary patterns, increased the release of bio-limiting nutrients to marine systems and increased the consumption of atmospheric CO₂ through biologic productivity and silicate mineral weathering. Evidence is presented for occurrences of forested ecosystems in swamplands in deltaic coastal settings, across a range of seasonally-drained floodplain overbank environments, and even in what were likely terraced interfluve landscapes during the Givetian in the Appalachian basin. Evidence is also presented that chemical weathering in paleosols on alluvial plains in the Appalachian basin may have increased from the Ordovician through the Middle Devonian. Temporal correlation of terrestrial and marine strata is essential in order to understand the potential cause and effect relationships between changes in Devonian weathering systems and marine environmental, ecological and geochemical conditions. Over 450 m of nearly continuous outcrop exposure along Plattekill Creek in West Saugerties, New York, was measured in order to develop a sequence-stratigraphic framework, using alluvial stacking-pattern analysis. The analysis reveals several orders of cyclicity that correspond with Acadian tectophases and previously documented marine depositional sequences. Paleo-precipitation for 37 paleosol profiles was estimated using the CALMAG proxy, a geochemical ratio from bulk soil material in vertic paleosols, which suggests dominantly wet paleoclimates throughout the Middle Devonian, an interpretation also supported by micromorphological data. The paleosol calcite paleobarometer was used to estimate atmospheric CO₂ decline related to the development of forested ecosystems, as well as determine the initial atmospheric pCO₂ at the onset of forestation. The timing of calcite precipitation in relation to the soil saturation state and soil-atmosphere connectivity was investigated in a modern Vertisol (smectitic, clay-rich soil, seasonally saturated) in Brazoria County, Texas, U.S.A., which is an excellent modern analog to forested paleosols in the Appalachian basin. A luminescent phase of calcite formed during the water-saturated portion of the year, negating its use for pCO₂ estimations. A non-luminescent phase formed during the well-drained portion of the year when atmospheric CO₂ mixed with soil-respired CO₂ and is therefore useful for pCO₂ estimation. From these results a model is presented that independently tests the saturation state of a paleosol at the time of pedogenic carbonate precipitation.
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.

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