Theses/Dissertations - Geosciences

Permanent URI for this collectionhttps://hdl.handle.net/2104/4784

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Hydrogeologic assessment of the Brazos River alluvial aquifer : Waco to Marlin, Texas
(1990-05) Harlan, Scott K.; Yelderman, Joe C.
The Brazos River alluvial aquifer is a shallow unconfined aquifer within the alluvial deposits along the Brazos River. The deposits include the floodplain and terrace material which are comprised of clay, silt, sand, and gravel. Thicknesses of the alluvial deposits range up to 80 feet. Groundwater in the terraces is restricted to domestic and livestock wells producing less than 50 gpm. Irrigation wells located in the floodplain may occasionally exceed 800 gpm. Flow directions in the terraces are toward the nearest stream dissection. Flow in the floodplain is toward the Brazos River and slightly downstream. Recharge to the aquifers consists primarily of rainfall recharging the terrace and floodplain surfaces as well as subsurface lateral inflow and recharge from losing streams and surface water bodies. Terrace deposits form minor aquifers that influence the hydrogeology of the floodplain aquifer system. Analysis of the water budget for the study area indicates that a portion of the Brazos River recharge originates from the terrace deposits. This recharge is transmitted through the Lower Taylor Marl Formation, the primary bedrock unit in the area, as lateral recharge into the adjacent floodplain aquifer. Estimates of hydraulic conductivities for the Lower Taylor Marl, as determined from this study, range from 1.45 x 10^-7 to 5.52 x 10^-7 cm/s. Hydrochemical analysis indicates that the groundwater in the Brazos River alluvial aquifer is primarily a calcium bicarbonate water. There is, however, significant variation within the study area. Analysis of chemical data by numerous methods indicate that although there are some trends within the study area, there are no mappable groundwater facies. Statistical analysis of a selected sample set indicate that there are significantly higher concentrations of some ions in the floodplain aquifer than in the terrace systems. Variations in measured parameters are a function of recharge-discharge relationships, flow paths, residence time and mineralogic differences in the aquifer matrix. A two-dimensional flow model is presented that describes the hydrochemical evolution in the aquifer.
Monitoring the Trinity Aquifer in McLennan County, Texas : an assessment and strategy for the Southern Trinity Groundwater Conservation District.
(2024-05) Sowders, Rebekah Lynn, 1999-; Yelderman, Joe C.
Groundwater is an important water source in the State of Texas, especially along the rapidly developing I-35 corridor. Understanding aquifer water level trends is helpful to groundwater management and conservation efforts. Groundwater levels can fluctuate for a variety of reasons and are often difficult to interpret. Recent technological advances allow groundwater managers to capture much more data on aquifer levels than previously possible; however, the density of the more detailed data make interpretation difficult, especially when trying to relate cause and effect. Monitoring aquifer levels is a major responsibility of Groundwater Conservation Districts (GCDs). This study provides an assessment and strategy for the Southern Trinity Groundwater Conservation District (STGCD) to improve data collection methods and aid interpretations for the confined portion of the Trinity Aquifer in McLennan County, Texas.
The influence of the Venusian atmosphere on the impact crater record.
(2024-05) Lee, Jeff S., 1964-; James, Peter Benjamin.
Enigmatic Venus has long been a subject of intense fascination. It has been called “Earth’s twin,” and yet it is encapsulated by an atmosphere of carbon dioxide and sulfurous gases that generates a surface pressure of 93 bars and cloud-level wind speeds of 100 m/s. The planet’s atmosphere protects its planet from asteroid impacts so effectively that only ~900 craters ranging in diameter from ~1.5 km to 270 km have formed on its ~800-Myr-old surface. However, the evolution of this “atmospheric shield” remains uncertain. It has been suggested that extensive volcanism has thickened the atmosphere. Alternatively, it has been postulated that solar wind stripping of ionospheric molecules has depleted the atmosphere to what it is today. However, the dominant mechanism that has driven the evolution of the Venusian atmosphere throughout the history of its current surface has remained largely unresolved in the literature. This work employs an in-house Fourth Order Runge-Kutta MATLAB® code (Horus Geb) to simulate the Venusian crater record with two asteroid population density models. The corresponding surface ages were determined to be 100 Myr and more credibly 800 Myr. Presented in this thesis is the first direct evidence that the evolution of the Venusian atmosphere has been dominated by “atmosphere thickening,” and consequently, the density of the atmosphere has increased over the history of its surface.
Elastic thermobarometry on metapelites and igneous rocks across the crustal section of the Famatinian Arc, Argentina.
(2023-08) Giovanini, Emanuel, 1997-; Befus, Kenneth S.
Determination of the pressures and temperatures at which rocks form is crucial to understanding petrologic processes in Earth. Elastic thermobarometry is a new, simple, technique that has shown early potential to accurately constrain the temperature and pressure conditions of rock formation using only low-cost Raman spectroscopy. Here, I performed the first crustal-scale application of elastic thermobarometry to demonstrate its extent and limitations. I applied elastic thermobarometry on metasedimentary and igneous rocks along two transects through the crustal section at Sierra Valle Fertil – La Huerta, Argentina. Quartz-in-garnet in migmatites recovers pressure ranging from 120 to 1374 MPa. Zircon-in-garnet thermometry from the same rocks estimates temperatures between 623 to 1512 °C. Finally, I evaluated possible applications on inclusion-host systems from igneous, marble, and metasedimentary rocks. My work shows that elastic thermobarometry can be a useful tool in combination with other techniques, but I encountered limitations when applied to high temperature rocks.
Leaf-level molecular markers of temperature, light, and water stress.
(2023-08) Wang, Zhao, 1990-; Hockaday, William C., 1979-
Few biomarker proxies inform terrestrial climates and ecosystem variables on geological time scales, probably because the reconstructions are mostly based on the lacustrine or oceanographic lens. Leaf lipids are valuable tools for the reconstruction of terrestrial paleoclimates since one of the lipids’ functional roles is to respond/adapt to environmental abiotic factors in the context of the ecosystem. However, two major obstacles have prevented the leaf-lipid proxies from applying to multifaceted plant physiological and geochemical issues to gain insights into the climate. One is that traditional lipid analysis requiring lipid extraction with follow-up cleaning step(s) prior to mass-spectrometry analysis, is considered as time-consuming and labor-intensive. The other is a lack of systematic investigation of the leaf lipids in modern plants in response to environmental factors. Therefore, the original research in this dissertation is divided into three themes involving leaf lipids in modern plants systematically varying with dynamic natural environmental abiotic factors. The first theme is designed for developing a feasible analytical method to extract and fractionate complicated leaf lipids concurrently on large-sample sets to improve statistical treatments. The lipids in leaves and lacustrine sediment are efficiently separated based on functional groups with a combination of adsorbents and solvents using pressurized solvent extraction with an in-cell cleanup method. The second theme is oriented toward understanding the responses of leaf lipids in deciduous and evergreen species to ambient-environmental abiotic factors (temperature, light, and water) and reconstructing seasonality using multi-lipid models. In the models, the seasonal variations of temperature and light absorbed by the canopy were correctly predicted by a multitude of leaf lipids, including leaf wax (n-alkanes, n-alkanols, n-alkanoic acids) and membrane lipids (sterols and unsaturated fatty acids). The third theme concerns leaf lipids in response to microclimates and potential driving mechanisms for the responses. Leaf lipid profiles are influenced by interactions between micro- and macro-climates with a water reservation strategy dependency. Leaf wax for both species changed with leaf water content and leaf-level light irradiance influenced by topography, seasons, and overstory canopy structure while leaf isoprenoids varied with changing light irradiance (leaf-level and overstory canopy structure) associated with the monthly temperature changes.
Reconstructing the early Paleocene light environments using fossil Platanites from the San Juan Basin, New Mexico, and its implications for stomatal pCO2 reconstructions.
(2023-08) Geng, Jie, 1997-; Peppe, Daniel J.
In the last two decades, stomatal proxies have been extensively used to reconstruct the concentrations of paleoatmospheric CO2 (pCO2) based on the well-established negative correlation between stomatal density (SD) and pCO2. However, various light environments within a fossil flora, known to influence many plant traits, including SD, were rarely discussed in most previous pCO2 reconstructions. We collected one well-preserved early Paleocene flora from the San Juan Basin, New Mexico, that is dominated by Platanites. We then analyzed the light environment of this flora based on leaf epidermal cell wall undulations, quantified by undulation index (UI), and the range of leaf carbon isotope. We found a negative correlation between UI and SD, which indicates that leaves under higher light intensities produce higher SD. Importantly, we observed a positive correlation between UI and reconstructed pCO2 using a leaf gas-exchange model, and we recommend future pCO2 reconstructions using stomatal proxies also assess variations caused by canopy light environments.
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.
Using Sycamore leaves to reconstruct ancient light environments.
(May 2023) Thorne, Desirae E., 1999-; Peppe, Daniel J.
Light environments strongly influence the composition and structure of terrestrial ecosystems and climates. Further, light intensity impacts both a plant’s leaf morphologic traits and its chemical composition, making it possible to quantify how these variables change in response to light intensity. Thus, it is possible to use leaf morphology and chemical composition to reconstruct ancient light environments, which can provide critical insights into past environments. Here, we present results focused on the development of a proxy for light availability using leaf size and shape (physiognomy) and chemical composition from modern Sycamore leaves that were grown under varying degrees of light availability in an outdoor light experiment. We found notable differences in leaf physiognomic variables, such as leaf area and perimeter, across light environments; and results from 13C NMR spectroscopy also indicate differences between light environments, with more abundant in lipids and less abundant in lignin found in low light conditions. Physiognomic and geochemical data were used to develop three different multivariate models for predicting daily light integral (DLI) that can applied to the fossil record. Using these models, we analyzed early Paleocene Platanites fossil leaves from the San Juan Basin, New Mexico to reconstructed ancient light conditions to help understand light availability and its impacts on the ecosystem and plant communities of early Paleocene.
Structure-reactivity mechanisms of organic matter sorption and photochemical transformation in aqueous environments.
(May 2023) Leonce, Burke C., 1987-; Hockaday, William C., 1979-
Black carbon produced from vegetation fires accounts for 15% of soil organic carbon and the dissolved component makes up 10% of organic carbon transported by rivers to the oceans annually. The association of organic carbon with metal oxides and its photochemical transformation are critical factors controlling C turnover in soils and aquatic systems. However, the influence of chemical structure on photodegradation of dissolved organic matter and its sorption to metal oxides remains questionable. The original research in this dissertation is aimed towards better understanding structure-reactivity mechanisms that control organic matter sorption to metal oxides and its photodegradation in aquatic environments. The molar heat of sorption of lignin monomers onto ferrihydrite was 1.17 kJ mol-1 and occurred via an outer-sphere mechanism involving multiple points of attachment. Sorption of lignin monomers was characterized by an exchangeable fraction that was bound to surface sites and within unblocked intraparticle pores and an unexchangeable fraction that was not accessible and/or removable by simple ion exchange. Plant biomass type and its processing via charring were significant drivers of dissolved organic matter (DOM) photolability and its sorption to nano-crystalline boehmite. The photo-bleaching behavior of DOM was captured by a three-component energy-based model. The first component was resistant to photobleaching, whereas the second and third components required a mean energy flux of 42-204 kJ m-2 and 168-1540 kJ m-2, respectively. Model predictions showed that an increase in vegetative fires would decrease photodegradative contributions to DOM cycling in the conifer-dominated east Texas, increase contributions in the hardwood shrub-dominated west, but have no effect in the grass-dominated central regions. The sorption of DOM to nano-crystalline boehmite was related to the preponderance of alkyl attachments to the aromatic backbone. Photolysis of DOM reduced the complexity and total energy of sorption for DOM thereby suggesting that solar-exposed DOM will be less prone to being sorbed, sorbed strongly and hence preserved via sorptive preservation on metal oxide colloids.
Quaternary landscape evolution, pedology, and geoarchaeology in central Texas.
(May 2023) Taormina, Rebecca A., 1991-; Nordt, Lee C.
Central Texas provides a unique environment as a climate ecotone for studying processes of river incision, deposition, and soil formation. This is the first study in central Texas focused on alluvial floodplain and terrace formation of the Brazos and Bosque rivers. Additionally, Buttermilk Creek provides a view of late Quaternary landscape evolution in central Texas along a low-order tributary. The late Quaternary history of central Texas is a complex story of climate and hydrologic changes, sediment supply, and human interaction. From >60 ka near the transition of MIS 5 to 4 to historic times through the end of MIS 1, the stream systems have recorded changes as rivers incised and aggraded.
Identification of a thermal maturation high, revised maturity map, and production trends of the Late Devonian Duvernay Formation, Alberta, Canada.
(May 2023) Yeates, David W., 1990-; Atchley, Stacy C.
The Late Devonian Duvernay Formation in the Western Canada Sedimentary Basin is a prolific shale reservoir that has been developed since 2010 and produced 250 million barrels of oil equivalent. Regional thermal maturity trends across central and southern Alberta published in the literature are poorly understood and inconsistent with produced fluid types. The focus of this dissertation is to refine thermal maturity trends of the Duvernay Formation. The Duvernay is subdivided into three hydrocarbon production areas that are, from west to east, Kaybob, Willesden-Green, and Innisfail. The maturity proxies used in this study are from solid-state 13C Nuclear Magnetic Resonance (NMR) and Rock Eval’s Tmax along with publicly available Tmax data, produced fluid types, and the structural burial depth trends across the basin. Thermal maturity across these areas increases to the southwest except for Willesden-Green. The southern portion of the Innisfail region reaches oil maturity whereas Kaybob ranges from oil to gas mature. Willesden-Green is markedly more mature than Kaybob as indicated by NMR (P=0.05) and Tmax (P=0.00) proxies even though samples from both areas were collected at similar depths (P=0.24). This thermally anomalous trend is named the Willesden-Green Maturity High (WGMH). The origin of the WGMH is interpreted to be related to an increase in geothermal gradient induced by the convective flow of hydrothermal fluids through a fault and fracture network stemming from the reactivation of the Snowbird Tectonic Zone during the Laramide Orogeny. Successful Duverney hydrocarbon production is related to both thermal catagenesis and optimal reservoir mineralogic composition as estimated from whole core elemental geochemistry. Elemental geochemistry was measured from continuous whole core at a 1-m sample interval using handheld X-ray fluorescence (XRF). Major elements are used as a proxy for mineralogy and redox-sensitive trace element enrichment as an indicator of depositional anoxia. Silica and calcium are used to estimate the relative abundance of quartz and calcite, respectively. High quartz and/or calcite mineral proportions increase rock brittleness and susceptibility to induced fracture stimulation. The eastern portion of the Kaybob region has the most productive oil and gas wells and correspondingly high concentrations of silica and redox-sensitive trace metals.
Unstressed groundwater flow in the Brazos River Alluvium Aquifer with implications for temporal ranges in groundwater to surface water interactions.
(May 2023) McVea, Jairon, 1998-; Yelderman, Joe C.
Groundwater flow paths and flow rates through alluvium aquifers are often oversimplified. This oversimplification may be due to sediment description limitations or aquifer properties obtained using well hydraulics that assume homogeneity. Groundwater travel times to the Brazos River channel can be longer than anticipated when the aquifer gradient is low and flow paths encounter heterogeneity within the lithologic framework. Conversely, travel times to the river channel can be less than anticipated when gradients are steep and homogeneous coarse sediment dominate the lithology within the aquifer while connecting directly to the river. This thesis investigates unstressed groundwater flow rates and flow paths under natural conditions using detailed lithologic logs to recreate more realistic heterogeneity of the Brazos River Alluvium Aquifer characteristics and a 2D finite element steady state model. These estimations provide important insight for surface to groundwater interactions within alluvium aquifers.
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.
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.
Seismic tomography of the former southern margin of Laurentia using teleseismic P and local pg phases.
(December 2022) Coulibaly, Koundienetia Aicha, 1997-; Pulliam, Jay.
The compositions, lateral and depth extent, and physical characteristics of geological features in the Texas-Oklahoma region are poorly constrained, just as the events that created them are poorly understood. We used EarthScope’s Transportable Array stations (2008-12) and TexNet stations (2018-present) to produce a 3D model of the region’s crust and upper mantle via seismic traveltime tomography using teleseismic P and local Pg arrivals. The combination of these two arrival types imposes strong constraints on the crust and upper mantle. The resulting tomographic model reveals a fast velocity anomaly in the mantle beneath west Texas, which may be related to subsidence that created the deep Delaware Basin. In east Texas, near the Louisiana border, a fast anomaly extends through the crust in the vicinity of the Sabine Uplift, although it does not coincide with the shallowest expressions of the Uplift. Although the Anadarko Basin appears prominently in the model’s crust, the Southern Oklahoma Aulacogen cannot be identified.
Seismic site characterization via joint modeling of horizontal-to-vertical spectral ratios and surface wave dispersion : developing and validating a geophysical tool for deciphering Quaternary stratigraphic architecture of the Monahans dune field, West Texas.
(December 2022) Spears, Brady, 1996-; Pulliam, Jay.; Pulliam, Jay.
Quaternary deposition for the Monahans dune system is reflected in its stratigraphic architecture through various periods of dune accretion, stabilization, and erosion as well as buried clay, carbonate-rich soils, and playa lake deposits. The complex and discontinuous stratigraphy of Monahans is difficult to capture without extensive borehole investigation. Shallow seismic techniques using Horizontal-to-Vertical Spectral Ratios (HVSR) and surface wave dispersion offer a cost-effective alternative to deciphering Quaternary architecture, but inverse models are subject to ambiguity and nonuniqueness. We jointly model HVSR and surface wave phase velocity dispersion measurements via global optimization to produce best-fit 1D shear wave velocity models for the interpretation of geologic structure and use statistical tools, including posterior probability distributions and parameter correlations, to demonstrate that joint modeling has the potential to impose stronger constraints on model parameters than modeling either seismic dataset alone.
Impact induced porosity of terrestrial impact craters : a gravity study of Meteor Crater.
(August 2022) Mitchell, Christopher D., 1995-; James, Peter Benjamin.
In this project we gathered and interpreted gravity anomaly data at Meteor Crater, and we used these data to constrain the porosity variations across Meteor Crater that were induced by the crater-forming impact event. We performed a gravity survey at the crater and merged these new data with legacy gravity survey data. From the resulting merged gravity data set, we generated a reduced anomaly map and created a model to estimate the gravitational effects of several stratigraphic units across Meteor Crater. Finally, we used a Bayesian inversion scheme to infer the bulk density and porosity of each stratigraphic unit. The models reflect the creation of impact-induced porosity of ~5-10% around and beneath the crater, supporting previous findings with novel methods and data.
Gravitational indications of subduction on Venus.
(August 2022) Dame, Rudger, 1993-; James, Peter Benjamin.
While Venus lacks global plate tectonics, there has been evidence of localized subduction on Venus. The goal of this study is to observe and forward model the gravity gradients of a subducted slabs on Earth and Venus. Our modeled results are consistent with subduction in at least three locations on Venus: Artemis Corona, Quetzalpetlatl Corona, and Astkhik Plateau. We also have identified a trend at terrestrial and Venusian subduction zones of a higher geothermal gradient on the overriding plate side of the trench and a lower geothermal gradient on the outboard side. The modeled subducting slabs on Earth and Venus are found to be negatively buoyant. However, the Venus slabs tended to be slightly less negatively buoyant. We hope that these methods will be repeated for smaller corona once VERITAS’s gravity data has been recovered.
Application of machine learning and magnetotellurics to aid in subsurface characterization of petroleum and geothermal reservoirs.
(August 2022) Rau, Elisabeth G., 1994-; Atchley, Stacy C.
Energy is the foundation of society and with future energy demand expected to increase significantly over the next few decades, solutions contributing to future energy resources are of high interest scientifically, geopolitically, and economically. Data analytics and machine learning provide useful tools to more efficiently and cost-effectively produce petroleum and geothermal resources vital for our energy future. Supervised and unsupervised machine learning can aid in the prediction of sedimentological and reservoir attributes in wells lacking core control to better and more efficiently characterize subsurface petroleum reservoirs. Using tree-based machine learning models, core-observed depositional attributes from the Late Devonian Duvernay Formation in Alberta, Canada may be predicted in wells lacking core control when class proportion and thickness conditions are met. Unsupervised machine learning technique, non-negative matrix factorization with k-means clustering (NMFk), automatically identifies reservoir significance, undetected through the traditional deterministic modelling, within the Duvernay Formation without calibration to core observations. The application of NMFk with petrophysical data may assist in highlighting intervals of interest in advance of core descriptions reducing observer inconsistency and bias and enhancing the quality and relevance of core description for reservoir correlation and mapping. Machine learning methods provide precise, consistent, and objective petrophysical interpretations and reservoir characterization, and increases the consistency and accuracy of resource assessment for petroleum exploration and production. Unsupervised machine learning and magnetotellurics are useful analytical tools to assess prospective geothermal resources in the Tularosa Basin of south-central New Mexico based on heat flow, temperature, porosity, and permeability. The unsupervised machine learning method, NMFk, identifies locations with the highest likelihood of geothermal success, and the passive geophysical method, magnetotellurics can detect subsurface geothermal prospects. The integration of NMFk and MT can provide a 3D assessment of heat flow, temperature, and permeability for geothermal exploration. This research provides innovative methods to aid in the development of efficient and cost-effective approaches for future energy exploration and production.

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