Browsing by Author "Stern, Robert J."
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Item Age, Geochemistry, and Emplacement of the ~40-Ma Baneh Granite-Appinite Complex in a Transpressional Tectonic Regime, Zagros Suture Zone, Northwest Iran(Taylor & Francis Inc, 2018-01-12) Azizi, Hossein; Hadad, Sepideh; Stern, Robert J.; Asahara, Yoshihiro; 0000-0002-8083-4632 (Stern, RJ); 284885305 (Stern, RJ); Stern, Robert J.The Baneh plutonic complex is situated in the Zagros suture zone of northwest Iran between the Arabian and Eurasian plates. This complex is divided into granite and appinite groups. Zircon U-Pb dating shows that granites crystallized 41-38 million years ago but appinites experience more protracted magmatic evolution, from at 52 to 38 Ma. Whole-rock chemical compositions show significant major and trace element variations between the two lithologies. Granitic rocks are more evolved, with high contents of SiO₂ (62.4-77.0 wt%), low contents of TiO₂ (0.25 wt%), MgO (0.05-1.57 wt%), and Fe₂O₃ (0.40-4.06 wt%) and high contents of Na₂O + K₂O (approximate to 10 wt%). In contrast, appinites have low contents of SiO₂ (51.0-57.0 wt%) and K₂O (<2.1 wt%) and high Fe₂O₃ (6.4-9.35 wt%), MgO (2.0-9.9 wt%), and Mg number (Mg# = 35-76). The concentration of rare earth elements in the appinites is higher than in granitic rocks, making it difficult to form granites solely by fractionation of appinite magma. (⁸⁷Sr/⁸⁶Sr)ᵢ and ε_{Nd(40 Ma)} in both groups are similar, from 0.7045 to 0.7061 and -1.2 to +2.6, except for a primitive gabbroic dike with ε_{Nd(40 Ma)}) = +9.9. Appinites show mainly typical I-type characteristics, but granites have some S-type characteristics. The sigmoidal shape of the Baneh pluton and its emplacement into deformed Cretaceous shales and limestone showing kink bands, asymmetric and recumbent folds in a broad contact zone, with pervasive ductile to brittle structures in both host rocks and intrusion, indicate that magma emplacement was controlled by a transpressional tectonic regime, perhaps developed during early stages in the collision of Arabia and Eurasian plates.Item Commentary on JGR-Sold Earth Paper “Deep Seismic Structure Across the Southernmost Mariana Trench: Implications for Arc Rifting and Plate Hydration” By Wan et al.(Blackwell Publishing Ltd, 2019-05-06) Stern, Robert J.; 0000-0002-8083-4632 (Stern, RJ); 284885305 (Stern, RJ); Stern, Robert J.No abstract available.Item Comprehensive Analysis of Global Mid Ocean Ridge and Mariana Convergent Margin Hydrothermal Systems Tectonics, Fluid Chemistry and Vent Biota(2020-05) Hetti Pathirannehelage, Diluni Ayeshika Wimalaratne; 0000-0003-0371-1636 (Hetti Pathirannehelage, DAW); Stern, Robert J.This study is a multidisciplinary data integration and metadata analysis for mid-ocean ridge (MOR) and Mariana intra oceanic convergent margin hydrothermal vents including fluids and biota. We compiled separate databases for MOR and Mariana hydrothermal vent parameters and their vent biota using published and on-line information managed by government agencies and other research institutes. The vent parameter databases are compiled under the categories of setting, vent field name, vent field number, name, latitude, longitude, alias, vent sites, smoker type and chimney composition, host rocks, full spreading rate, depth, temperature, pH, total Fe, (³He/⁴He)/Rₐ, CO₂, CH₄, H₂, H₂S, SO₄²⁻ ions, chlorinity, operations and references. MOR database for vent parameters includes 449 individual hydrothermal vents grouped into 73 vent fields at global divergent margins. The vent organism database of MOR vents includes 672 species belong to 72 individual vents. Mariana vent summary database includes 47 individual hydrothermal vents belong to four different tectonic settings: the forearc (FAR), arc (ARC), backarc (BAB) and the southern Mariana trough (SMT). Database for Mariana biota include vent animals for 31 vents of the above settings. We considered vent depth, fluid temperature, pH, total Fe, Mn, helium isotopic ratio ((³He/⁴He)/Rₐ), fluid gases (CO₂,CH₄, H₂, H₂S), SO₄²⁻ ions and chlorinity of the fluids for statistical analysis. In addition to these parameters, for MOR vents full spreading rate was also considered for statistical analysis. To overcome non-linear data distributions and small number of observations for some vent parameters, we used purely nonparametric statistical procedures. We assessed vent fluid parameters first for correlations with key parameters spreading rate (for MOR only), summit depth, fluid temperature and fluid chlorinity. Second, we compared different segments (MOR segments and Mariana tectonic settings) based on vent parameters. Similarities between the vent organisms in different tectonic segments were assessed using Sörensen similarity indices; for MOR vents at both genera and species levels; and for Mariana only for genus level. Our results for MORs show that even if MOR hydrothermal systems are associated with simple divergent margin tectonism, they are remarkably similar despite having differences in both fluid chemistry and biota distribution regardless of the ocean and the rate of spreading. Vent fluid temperature, pH, Fe, Mn, CO₂, H₂, SO₄²⁻ ion and chlorinity are independent of the spreading rate. Fluid temperature does control pH, Fe and H₂S. Brine separation might influence gases such as helium isotopic ratio and CO₂ in venting fluids. Highest similarities of the macro organisms are seen in the Indian Ocean ridges and the greatest differences are observed in the Pacific Ocean ridges. Integration of tectonics, fluid chemistry and vent biota of Mariana convergent margin vents demonstrate that Mariana vent groups are more diverse than global mid-ocean ridge vents and that the southernmost Marianas most resembles mid-ocean ridge (MOR) type venting, the other tectonic groups are quite different than MOR vents.Item Eocene Initiation of the Cascadia Subduction Zone: A Second Example of Plume-Induced Subduction Initiation?(Geological Society of America, 2019-04-15) Stern, Robert J.; Dumitru, T. A.; Stern, Robert J.The existing paradigm for the major ca. 56-48 Ma subduction zone reorganization in the Pacific Northwest of North America is that: (1) the Siletzia large igneous province erupted offshore to the west of North America, forming an oceanic plateau; (2) Siletzia then collided with North America, clogging the Pacific Northwest segment of the Cordilleran subduction zone; and (3) the oceanic lithosphere west of Siletzia then ruptured to initiate the new Cascadia subduction zone. Oceanic lithosphere is strong and difficult to rupture, so this would represent a rare example of such a rupture initiating a new subduction zone. This paper explores an alternative hypothesis for the reorganization, a plume-induced subduction initiation (PISI) mechanism, which has previously been applied to the initiation of Caribbean plate subduction zones in the Cretaceous. In this PISI hypothesis, a newly formed, ~1200-km-diameter Yellowstone mantle plume head rose at ca. 55 Ma beneath western North America, generating Siletzia in situ on the North American margin, as well as generating the ~1700-km-long Challis-Kamloops volcanic belt ~600 km to the east of Siletzia. This destroyed the existing Cordilleran subduction zone and allowed the new Cascadia subduction zone to form by collapse of thermally weakened oceanic lithosphere over the hot western margin of the plume head. This PISI hypothesis provides an integrated framework for understanding Siletzia, the Challis-Kamloops belt, Eocene core complexes from Idaho (U.S.) to British Columbia (Canada), underplated mafic rocks beneath Oregon and Washington (U.S.), post-17 Ma manifestations of the Yellowstone plume, and geophysical characteristics of the lithosphere beneath the Pacific Northwest. © 2019 The Authors.Item Eruption of South Sarigan Seamount, Northern Mariana Islands: Insights into Hazards from Submarine Volcanic Eruptions(Oceanography Society, 2014-06) Embley, R. W.; Tamura, Y.; Merle, S. G.; Sato, T.; Shizuka, O. I.; Chadwick Jr., W. W.; Wiens, D. A.; Shore, P.; Stern, Robert J.; 0000 0003 5076 6787 (Stern, RJ); 284885305 (Stern, RJ); Stern, Robert J.The eruption of South Sarigan Seamount in the southern Mariana arc in May 2010 is a reminder of how little we know about the hazards associated with submarine explosive eruptions or how to predict these types of eruptions. Monitored by local seismometers and distant hydrophones, the eruption from ~ 200 m water depth produced a gas and ash plume that breached the sea surface and rose ~ 12 km into the atmosphere. This is one of the first instances for which a wide range of preand post-eruption observations allow characterization of such an event on a shallow submarine volcanic arc volcano. Comparison of bathymetric surveys before and after the eruptions of the South Sarigan Seamount reveals the eruption produced a 350 m diameter crater, deeply breached on the west side, and a broad apron downslope with deposits > 50 m thick. The breached summit crater formed within a pre-eruption dome-shaped summit composed of andesite lavas. Dives with the Japan Agency for Marine-Earth Science and Technology Hyper-Dolphin remotely operated vehicle sampled the wall of the crater and the downslope deposits, which consist of andesite lava blocks lying on pumiceous gravel and sand. Chemical analyses show that the andesite pumice is probably juvenile material from the eruption. The unexpected eruption of this seamount, one of many poorly studied shallow seamounts of comparable size along the Mariana and other volcanic arcs, underscores our lack of understanding of submarine hazards associated with submarine volcanism.Item Evaluation of Magma Flow and Emplacement Mechanisms of the Mafic Dulce-Platoro Dike Swarm, NW New Mexico and SW Colorado Using Magnetic Susceptibility Fabrics(2022-12-01T06:00:00.000Z) Johnson, Samuel Paul 7/17/1990-; Geissman, John W.; Brikowski, Thomas H.; Ferguson, John F.; Stern, Robert J.Magnetic fabric investigations of magmatic dikes have been frequently employed for over four decades to estimate magma flow directions to better understand volcanic and magmatic systems. Anisotropy of magnetic susceptibility fabric data were collected from 32 sites of the approximately 125km N-S, 25km E-W Platoro-Dulce dike swarm of late Oligocene age in northern central New Mexico and southern central Colorado, USA, to estimate magma flow directions. The Platoro Caldera in the Southern Rocky Mountain Volcanic Field at the northern end of the swarm, and the incipient Rio Grande rift to the east of the swarm, represent two potential sources for this mafic dike swarm. This study helps by considering two models of emplacement: one involving a magma flow regime that predicts generally steep magma ascent with no bias to horizontal component of flow or, alternatively, one that predicts generally shallower magma ascent with a south bias to the horizontal component of flow. Rock magnetic, paleomagnetic, and petrographic inspection of the dikes all show that the measured rock magnetic fabric is of primary origin at time of emplacement and thus that these dikes are permissible for estimating magma flow directions. A tentative conclusion based on inferred flow directions which demonstrate no bias for north or south horizontal flow directions but bias for steeply inclined vertical flow is that the Rio Grande rift likely acted the magma source and was responsible for the extension dominated tectonic stress field in the eastern San Juan Basin that controlled emplacement of the dikes, although the Platoro Caldera likely influenced local stress field conditions.Item Extraction of Seismic Properties and Models From, and Full Waveform Inversion of, Dispersed Seismic Waves(2022-12-01T06:00:00.000Z) Ren, Li; Zhu, Hejun; Ferraris, John P.; McMechan, George A.; Ferguson, John F.; Stern, Robert J.Surface waves, which propagate along boundaries between two different media, play an important role in resolving geological structures of different scales targeted from global seismology, exploration seismology, geotechnical engineering, to nondestructive testing. Over the past half century or so, different methods have been explored to process and invert surface waves for underground model properties, especially the shear wave velocity. However, there are still many problems waiting to be solved. Conventional dispersion curve inversion (DCI) is limited to 1-D model assumption and has increased uncertainty when the structure is complicated. It also requires picking of dispersion curves from field data, which is often a labor intensive process. Although, methods in the framework of full waveform inversion of surface waves yield models with good resolution, both laterally and vertically when carefully implemented and applied, they are computationally intensive and can easily suffer from the cycle skipping problem. Wave-equation based dispersion curve inversion method combine some of the advantages of those in conventional dispersion curve inversion and full waveform inversion, but also requires picking of dispersion curves from both field and synthetic data. This dissertation focuses to partially solve some of the above issues and leads to more work that can be done in the future. To automate the picking of dispersion curves from surface waves, which is required for many approaches for shallow-subsurface characterization using surface waves, my first project presents a convolutional-neural-network (CNN) based machine learning approach to automatically pick the curves for the fundamental and higher modes along the two azimuths of any 2D seismic profile. Various attributes such as amplitudes, coherency, and local phase velocity as well as frequency and wavenumber of dispersion curves are derived; different sub-sets of these are tested in the CNN training process to assess the best combinations. We use a U-net architecture that is modified to convert the conventional 2D image segmentation problem in the (f,k) domain into direct multi-mode curve fitting and a subsequent picking process. To make the automatic picking algorithm more practical, we (1) introduce a second loss function that combines conventional wavenumber residuals and curve slope residuals; (2) use the transfer learning strategy, in which the network is pre-trained with synthetic data and then with a relatively small portion of the field data, to improve the efficiency of the algorithm; (3) evaluate two categories of uncertainty, the epistemic uncertainty from the method itself and input data, and uncertainty from non-deterministic factors such as random initialization of model weights and random shuffle of samples in training in the CNN, and in GPU parallelism. The epistemic uncertainty is an important indicator of the picking quality and can be used as a weighting of data in subsequent inversion; (4) perform post-processing to determine the effective dispersive frequency range of the picked curves by using different criteria, such as long/short moving average ratios (MAR) of squared picked wavenumbers, posterior uncertainty etc. The effectiveness of the automatic picking process is demonstrated in this study through applications to a field OBN dataset where different modes of Scholte waves were recorded. To reduce cycle skipping in FWI and to increase resolution of the estimated model, my second project develops and illustrates concurrent elastic full-waveform inversion (FWI) of P and S body waves and Rayleigh waves using interleaved envelope- and waveform- based misfit functions, in a gradually-increasing frequency, multi-scale, inversion strategy, to estimated both lateral and horizontal variations of models, which breaks the 1D assumption of conventional DCI. Computing correlation coefficients between the observed and predicted data, and between the inverted and correct models, provides quantitative measures of the composite contributions, of the starting model, the chosen data flow, and the depth extent of the solution space, to the fits of the corresponding solutions. Treating the whole wavefield as a single data set means that it is not necessary to separate, or even to identify, different types of body and surface waves.Item Grignard Metathesis (GRIM) Polymerization for the Synthesis of Conjugated Block Copolymers Containing Regioregular Poly(3-Hexylthiophene)(2011-11-28) Stefan, Mihaela C.; Bhatt, Mahesh P.; Sista, P.; Magurudeniya, H. D.; Stern, Robert J.The synthesis of various conjugated block copolymers of regioregular poly(3-hexylthiophene) by Grignard metathesis (GRIM) polymerization is described. © 2012 The Royal Society of ChemistryItem Jurassic Igneous Rocks of the Central Sanandaj–Sirjan Zone (Iran) Mark a Propagating Continental Rift, Not a Magmatic Arc(Blackwell Publishing Ltd, 2019-04-29) Azizi, H.; Stern, Robert J.; 0000-0002-8083-4632 (Stern, RJ); 284885305 (Stern, RJ); Stern, Robert J.Jurassic igneous bodies of the Sanandaj–Sirjan zone (SaSZ) in SW Iran are generally considered as a magmatic arc but critical evaluation of modern geochronology, geochemistry and radiogenic isotopes challenges this conclusion. There is no evidence for sustained igneous activity along the ~1,200 km long SaSZ, as expected for a convergent plate margin; instead activity was brief at most sites and propagated NW at ~20 mm/a. Jurassic igneous rocks define a bimodal suite of gabbro-diorite and granite. Chemical and isotopic compositions of mafic rocks indicate subcontinental lithospheric mantle sources that mostly lacked subduction-related modifications. The arc-like features of S-type granites reflect massive involvement of Cadomian crust and younger sediments to generate felsic melts in response to mafic intrusions. We conclude that Jurassic SaSZ igneous activity occurred in a continental rift, not an arc. SaSZ igneous rocks do not indicate that subduction along the SW margin of Eurasia began in Jurassic time. © 2019 John Wiley & Sons LtdItem Statistical Treatment and Modeling of Geochemical Data of Volcanic Arcs(2019-05) Lieu, Warren K.; Stern, Robert J.This contribution concerns two projects based on statistical analysis of geochemical data of lava samples from global arc systems combined with standard geochemical treatments in order to extract trends, regularities and structures not readily apparent when done by studying individual volcanoes. Part I is an article "The robustness of Sr/Y and La/Yb as proxies for crust thickness in modern arcs." This paper considers three volcanic arcs – the Aleutians, Central America, and the Andes – and applies our understanding of trace element partitioning for four key elements and their dependence on pressure (i.e., depth) to derive crustal thicknesses along arcs and arc segments. We used geochemical data from the EarthChem.org repository and combined these with recent published igneous rock compositions vs. depth studies to derive crustal thickness profiles along modern arcs. We compare our methods with geophysical surveys to assess the viability of the correlation and our techniques. That the study at least partly agrees with geophysics is a boon for the conceptual methods we devised. That disagreements exist are, one, challenges for future geophysical surveys and geochemical studies to resolve and, two, a chance to interpret our results to reimagine and to incorporate existing theory of crustal processes into a framework that is consistent with our results. Some arc's Moho may not have the sharp boundary that it is beneath continents but becomes an exchange interface with magma rising from the mantle injecting into the crust at the same time that magma cumulates (from fractionation) and crustal residues (from partial melting of the crust) founder into the mantle. The upper mantle beneath some active arc segment is then suffused with cumulates and restites separated from the lower crust such that seismic imaging of the Moho is difficult and ambiguous. Part II, "Fractionation and delamination in arc crust genesis," constrains models of fractional crystallization to generate lavas of the Alaska-Aleutian arc. The modeled dataset contains ~2,500 lava samples from ~30 volcanoes. We simulate first-order Earth processes that are heterogeneous, widely variable, and may not be in thermodynamic equilibrium, but that follow some principals that are statistically resolvable. This scheme reveals crustal processes that are plausible and produces cumulates that are similar to exposed mid and lower arc crust in Alaska and the Pakistani Himalayas. These modeled cumulates have variable compositions and densities to create a stratified crustal column as in exposed crust. Estimates of the physical characteristics and quantities of mineral assemblages can be inferred from the simulated crust to give insights into the mid and lower crust of the Alaska-Aleutian arc. For example, that the model solutions provide the quantity of the hydrous mineral amphibole in a crustal column allows me to estimate the amount of water stored in the crust, and explore the consequences of that. Furthermore, the results of fractionation modeling can be combined with approximate crustal geotherms and mineral densities to estimate the amount and rate that these dense cumulate masses are likely to sink into the upper mantle.Item Subduction Initiation Dynamics along a Transform Fault Control Trench Curvature and Ophiolite Ages(Geological Society of America) Zhou, X.; Li, Z. -H; Gerya, T. V.; Stern, Robert J.; Xu, Z.; Zhang, J.; 284885305 (Stern, RJ); Stern, Robert J.Understanding how new subduction zones form is essential for complete articulation of plate tectonic theory. Formation of new subduction zones by collapse of oceanic transform faults or fracture zones is suggested on the basis of empirical evidence. This process has heretofore been investigated with two-dimensional (2-D) numerical models, which thus ignore its intrinsic three-dimensional (3-D) geometry, lateral propagation, and dynamics. Here, we investigate a 3-D thermomechanical model, in which old and thick oceanic lithosphere (plate) is separated by a transform fault from a thinner and younger oceanic plate containing a transform-orthogonal spreading ridge. The results suggest that the older plate starts to sink spontaneously at the ridge-transform fault junction, and then subduction initiation laterally propagates along the transform away from the ridge. Two key factors control the 3-D subduction initiation (SI) dynamics in nature: (1) the age of the sinking plate, which controls its negative buoyancy; and (2) the thermal structure of the overriding plate, which reflects its spreading history. Our numerical models not only shed new light on the SI dynamics of Cenozoic subduction zones (e.g., the Izu-Bonin-Mariana zone in the Pacific Ocean), but also have implications for fossil convergent plate margins (e.g., the Bitlis-Zagros suture zone, west of the Strait of Hormuz). In the latter case, systematic variations in ages of supra-subduction zone ophiolites may reflect diachronous SI and its lateral propagation. ©2018 Geological Society of America.Item The Muenster Uplift of North Texas: The Easternmost Expression of the Pennsylvanian Ancestral Rockies(2016-12) George, Mark C.; Stern, Robert J.The Muenster Uplift is a positive structural feature characterized by NW-SE trending reverse faults extending ~300 km (200 miles) in the subsurface from the Wichita Uplift in southwestern Oklahoma to the Ouachita fold and thrust belt in northeast Texas. It shares a similar structural style to other Late Paleozoic Ancestral Rockies basement-involved uplifts throughout the west-central United States. It is a strongly asymmetric structure, bounded by a fault to the SW, with considerable offset to the downthrown foreland Fort Worth Basin. Gravity strongly correlates with the uplift, with steep gradients on the SW. Seismic and well data indicate a thrust fault offsetting Precambrian basement by greater than 10,000’ (~3 km). The uplift began developing in Late Mississippian time and remained active through Late Pennsylvanian time. It has since remained as a positive structural element, although buried by Cretaceous sediments and has no surface expression. The Muenster Uplift played an important role in the depositional patterns and tectonic evolution of the Fort Worth Basin.Item The Robustness of Sr/Y and La/Yb as Proxies for Crust Thickness in Modern Arcs(Geological Society of America, 2019-03-29) Lieu, Warren K.; Stern, Robert J.; Lieu, Warren K.; Stern, Robert J.Trace element (TE) ratios of convergent-margin magmas have been found to vary systematically with arc crustal thicknesses. Here we use statistical smoothing techniques along with Sr/Y and La/Yb trace element Moho depth proxies to determine crustal thickness along the volcanic front for three arc segments: the Central Volcanic Zone of the Andes arc, the Central America arc at Nicaragua and Costa Rica, and segments of the Alaska-Aleutian Islands arc (northwesternmost USA). The results are comparable to those from seismic surveys. TE depth proxies give ~70 km crust thickness beneath the Central Volcanic Zone's Altiplano region and show thinner crust (60 km for La/Yb, 43 km for Sr/Y) as the volcanic line crosses into the Puna region. In Central America, the proxy analyses show crustal thickness changes between the Chorotega block and the Nicaragua depression, with both proxies agreeing for Nicaragua (~27 km) but with La/Yb giving considerable thicker (~45 km) crust than Sr/Y (~30 km) for Chorotega. For these two arc segments, the La/Yb proxy approximated the seismically inferred Moho depth to within 10 km for the entire profile, but the Sr/Y proxy-estimated crustal thicknesses diverge from those of the La/Yb proxy and seismic methods in the thin-crust regions. For the Alaska-Aleutian arc, both TE proxies indicate that crust varies from thick (~35 km) for the western Aleutian segment (175°E to 175°W), to thin (~22 km) for the transitional segment (175°W to 158°W), to thick (35+ km) for the eastern Alaska Peninsula (158°W to 150°W). Geophysical estimates favor a crustal thickness of 30-40 km for the same region. We propose that statistically treated geochemistry-based proxies can provide useful estimates of crustal thickness when estimates from Sr/Y and La/Yb agree. We investigated the disagreement in the Alaska-Aleutian case in more detail. Alaska-Aleutian crustal thickness was found to correlate with calc-alkaline (CA) versus tholeiitic (TH) segments of the arc, as represented by along-arc smoothing of the volcanoes' CA-TH indices. The thin crust of the transitional segment trends TH while the thicker crust of the flanking segments trend CA. We find that crustal thickness also plays a role in inferred magma flux (here approximated by volcano volume), with greater flux associated with thinner crust. Thin crust beneath the Alaska-Aleutian transitional segment may reflect continuing loss of cumulates from the lower crust and/or lithospheric mantle into the asthenosphere, leading to enhanced melting beneath this region. © 2019 The Authors.Item X-ray Fluorescence and Total Organic Carbon Analysis of Delaware Basin Ordovician Age Sediments in the Ellenburger and Simpson Groups of West Texas(2016-12) Cuyler, Joshua Robert; Stern, Robert J.Ordovician age hydrocarbons have been drilled in the Permian Basin of West Texas since the early 1940s and have produced over a billion barrels of oil with additional natural gas. The source rock for these previously drilled Ellenburger Group reservoirs has been suggested to be the Simpson Group shales, but limited total organic carbon studies and no x-ray fluorescence analysis has been performed on the Permian Basin Ordovician rocks to determine the overall lithology and trace element enrichment relative to total organic carbon to substantiate this statement. The majority of Ordovician hydrocarbon production has occurred in faulted and structural traps in the Ellenburger, but the hydrocarbons have a different hypothesized source due to generally low total organic carbon within this group. Trace element enrichments can serve as indicators of the presence of organic material and paleoredox conditions. This study utilizes x-ray fluorescence elemental data and total organic carbon data from Permian Basin Ordovician sediments to analyze general rock lithology and to understand whether biologically- and paleoredox-sensitive trace elements coincide with total organic carbon, and if so, can these similarities give insight to the organic enrichment of these sediments and the paleoredox conditions present during their deposition. The findings of this study suggest that the Simpson Group reflects a depositional environment with intermittent layers of sandstone, green shale, black shale, red shale, and a large percentage of carbonate suggesting a shallow water marine environment. The majority of trace elements that serve as useful proxies for total organic carbon within these sediments are mostly associated with the detrital shale influx and are not associated with biological activity or paleoredox conditions. The majority of the total organic carbon values for the Simpson Group and Ellenburger Group suggest a poor (<0.5 wt. % total organic carbon) source rock with limited potential to generate hydrocarbons though fair (.5-1 wt. % total organic carbon) to good (1-2 wt. % total organic carbon) values are present in a limited number of samples. X-ray fluorescence data indicates the presence of trace element enrichments in some samples, but no clear correlation with total organic carbon is recognized.