Powder River Basin Research Articles

Mineral dissolution and precipitation induced by hydraulic fracturing of a mudstone and a tight sandstone in the Powder River Basin, Wyoming, USA

Water-based hydraulic fracturing requires high-pressure injection of large quantities of water mixed with chemicals into the subsurface, where fluids contact mineral surfaces. Chemical imbalance between minerals and the injected fluids provides the potential for chemical reactions that may induce physical alterations to the rock. We investigate mineral reactivity during in situ water-rock interaction between unconventional reservoir rocks and hydraulic fracturing fluid. We characterized two unconventional reservoir rocks, a calcareous mudstone (B Bench of the Niobrara Formation) and a calcite-cemented sandstone (Wall Creek Member of the Frontier Formation) of the Powder River Basin, Wyoming, USA, and developed, analyzed, and quantified the aqueous geochemistry of a hydraulic fracturing fluid (HFF). These datasets informed the design of numerical simulations that predict mineral-HFF interactions at in situ conditions over a 31-day timeframe. The two unconventional reservoir rocks have similar mineral assemblages, albeit in different proportions, which leads to similar dissolution/precipitation reactions. Calcite, feldspar, and authigenic clay minerals begin to dissolve, and secondary calcite, anhydrite, and illite form. Calcite dissolution increases porosity of the B Bench from 2% to 2.9% and porosity of the Wall Creek from 5% to 5.8%. Mineral-fluid reactions manifest in flowback fluids as temporal geochemical trends consistent with limited field data.

Muddy sandstone, Powder River Basin: rejuvenation of an old play with horizontal drilling

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Carrier-Bed plays in the Denver and Powder River basins

Carrier-bed plays are a new type of unconventional oil play that are currently being developed in North America. The reservoirs are generally low quality because of any of the following: thin beds (heterolithic strata), diagenesis, or burrowing (heterogeneous, mixing of sandstones or carbonates and mudstones). The carrier beds are pervasively hydrocarbon saturated and can occur over an areally extensive (greater than than 50 square miles, greater than 129 square kilometers) area. These low-quality reservoirs generally do not meet traditional petrophysical cutoffs and because of the clay content can create low resistivity, low contrast pays. The reservoirs may be composed of clastics or carbonates or a mixture of both. A sub-category of a carrier-bed play is a halo play. Halo plays are the low permeability flanking edges of a conventional oil accumulation (i.e., waste zone or the fringe). The low reservoir quality is generally stratigraphic in origin (facies change from high quality to low quality reservoirs). Carrier-bed and halo plays are being developed with horizontal drilling and multistage hydraulic fracturing. Traditional vertical drilling yields marginal to uneconomic wells but are a clue to the existence of a carrier-bed play. This paper reviews Upper Cretaceous carrier bed plays in the Denver (Codell SandstoneMember of the Carlile Shale) and Powder River (Turner Sandy Member of the Carlile Shale) basins.

Distinction of strontium isotope ratios between water-soluble and bulk coal fly ash from the United States

Coal ash is one of the largest industrial waste streams in the United States and contains elevated concentrations of hazardous elements that could pose environmental and human health risks. Due to the relatively high strontium concentrations in coal ash and the distinctive 87Sr/86Sr ratios, strontium isotopes have been utilized to trace coal ash contaminants in impacted water resources. While previous studies have characterized the Sr isotope ratios for the water-soluble Sr derived from coal ash, the strontium isotopic composition of the bulk coal ash has not been systematically evaluated. In the current study, we report the 87Sr/86Sr ratios of bulk and water-soluble Sr in fly ash derived from coals of the three major coal-producing basins in the U.S., the Appalachian Basin, Illinois Basin, and Powder River Basin. The data show a wide range of 87Sr/86Sr ratios in the bulk fly ash samples (0.710788–0.722311), with the most radiogenic 87Sr/86Sr ratios in fly ash originating from Illinois Basin coals (0.718029 ± 0.003365; n = 16), followed by those from Appalachian Basin coals (0.712641 ± 0.000860; n = 16), and those from Powder River Basin coals (0.711663 ± 0.000489; n = 7). The 87Sr/86Sr ratios in the water leachates are significantly lower than the 87Sr/86Sr ratios of the bulk fly ash for Illinois Basin and Appalachian Basin (0.711660 ± 0.001172 and 0.710694 ± 0.000317, respectively, p-value < 0.01), whereas there is no significant difference for the Powder River Basin fly ash (0.711666 ± 0.000456, p-value = 0.13). These isotopic differences most likely reflect the different mineralogical compositions of the studied fly ash and the differential solubility of carbonate phases with low 87Sr/86Sr ratios relative to more radiogenic silicate phases. Overall, the distinction between the strontium isotope ratios of bulk fly ash versus water-soluble fly ash is important, as it refines the application of strontium isotopes as a forensic tracer for tracking coal ash spills and contamination in the environment.

Green and efficient two-step degradation approach for converting Powder River Basin coal into fuels/chemicals and insights into their chemical compositions

A green and efficient two-step degradation approach, including supercritical CO2/ethanol degradation and oxidation in aqueous hydrogen peroxide solution, was reported to convert Powder River Basin coal into fuels/chemicals. In total, 43.5 wt% liquid tar and 23.3 wt% oxidation products were obtained from the two-step degradation. The liquid tar was facilely separated into light oil and asphaltene, with yields of 27.3 wt% and 16.5 wt%, respectively. The first-step degradation has high energy recovery (50%) and low energy consumption ratio (minimum 0.17), indicating an energetic net energy gain. The light oil is a promising feedstock as clean liquid fuels due to its high H/C ratio (1.58) and heating value (34.56 MJ/kg). The asphaltene with lower H/C and O/C ratios but higher aromaticity (0.83) could be a good precursor for carbon materials. The light oil can be upgraded into clean liquid fuels by hydrodeoxygenation or used as feedstock for producing oxygenated chemicals because it is rich in oxygenated components. Phenols and aliphatic esters account for 74.2% of the volatile components in the light oil. High resolution mass spectrometric analysis revealed that the O1–O4 class species are dominant components with relative abundance of 71% in the light oil. Valuable carboxylic acids with total yields of 19.7 wt%, especially alkanedioic and alkanetricarboxylic acids, were produced from oxidation of the scCO2/ethanol degradation residue, which is a promising second-step degradation to utilize the residue. This study provides an efficient coal conversion processes for producing fuels/chemicals and reducing energy consumption and environmental impact.

A biosorption-based approach for selective extraction of rare earth elements from coal byproducts

Coal byproducts represent an abundant and untapped potential source of critical rare earth elements (REEs). In this study, we tested the efficacy of a biosorption-based approach to recover REEs from leachate solutions derived from North Dakota lignite coal and Powder River Basin (PRB) coal fly ash. A pairwise comparison was performed using a range of cell densities of two distinct bacteria, including an Escherichia coli strain previously genetically engineered for cell surface display of lanthanide binding tags, and Arthrobacter nicotianae, a native bacterium that exhibits high REE adsorption capacity. At optimal cell densities, we observed a recovery efficiency of 80% for total REEs and > 90% for middle and heavy REEs from the lignite leachate. Higher cell densities were required to achieve a similar total REE recovery efficiency in the PRB leachate due to its higher non-REE content, which negatively impacted light REE recovery. Despite the chemical complexity of both feedstocks, separation factors ≥ 30 were observed for Nd relative to nearly all non-REE metals after a single adsorption/desorption cycle, highlighting the high adsorption selectivity for REEs. Quantification of impurities in the extracted metal solutions revealed that Ca and Mg content in the leachate solutions play a dominant role in both the REE recovery yield and purity. The Mg/Ca impurities can be further reduced by incorporation of a low pH wash step between the adsorption and desorption steps, yielding extracted concentrates with a REE purity (mass fraction REE of total metals) of 80% and 50% for lignite and PRB, respectively. Thermodynamic speciation analysis of the REE-enriched eluents from both feedstocks suggests that at a post-biosorption hydroxide precipitation step can be employed to yield high purity total REE precipitates. Collectively, these results highlight the utility of biosorption for selective REE recovery from coal byproducts and pave the way for a sustainable route to diversify the REE supply chain.

Social license to operate during Wyoming's coalbed methane boom: Implications of private participation

Unconventional oil and gas (UOG) projects have emerged as fundamental, yet often controversial, components of contemporary energy systems. In contrast to the prevailing academic focus on sites of conflict, this paper explores why and how the social license to operate succeeds in UOG settings, or how private landowners accept or accommodate development. This paper applies the concept of social license to operate to landowner-industry relations during an episode of coalbed methane (CBM) development in the Powder River Basin, Wyoming. Conclusions draw on forty semi-structured interviews with stakeholders, including industry personnel, oil and gas attorneys, and surface owners that hosted CBM development. The findings indicate that mutual respect, procedural fairness, and trust were necessary preconditions of social license. These three preconditions created an opening for surface owners to effectively engage in private participation and advocate for their instrumental priorities. However, the key priority of surface owners to retain energy infrastructure, instead of demanding reclamation, has contributed to the existing U.S. land-use phenomenon of energy sprawl. Therefore, reclamation policy should aim to secure positive personal outcomes for private surface owners while mitigating against the cumulative environmental impacts of energy production.

Capacitance-Resistance Model Used for Integrated Detection of Water Production

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 19333, “Integrated Detection of Water Production in a Highly Heterogeneous and Tight Formation Using a CRM Model: A Case Study on Waterflooding Gaither Draw Unit, Wyoming, USA,” by Kailei Liu, China University of Geosciences; Xingru Wu, SPE, University of Oklahoma; and Kegang Ling, University of North Dakota, prepared for the 2019 International Petroleum Technology Conference, Beijing, 26–28 March. The paper has not been peer reviewed. Copyright 2019 International Petroleum Technology Conference. Reproduced by permission. The Gaither Draw unit is a heterogeneous tight formation with an average permeability of less than 0.1 md. After substantial water injection, there was no clear benefit of injected water for any producer. However, knowing the distribution of the injected water is critical for future well planning and quantification of injection efficiency. The objective of this study is to show how the capacitance-resistance model (CRM) was used on this field and how it validated the use of other independent methods. This paper demonstrates that integration of different sources of data in reservoir management is critical. Introduction Unlike numerical reservoir simulation, the CRM requires only the injection rates of each injector and the production rates of each producer as input to evaluate reservoir performance. The connectivity and the time constant that are estimated by fitting production rates can provide useful information about geological features and reservoir heterogeneity. With a clear understanding of reservoir heterogeneity, flow barriers and high-permeability zones can be identified. Significant reservoir heterogeneity may lead to poor sweep efficiency. These characteristic features make the CRM (the development of which is outlined in the complete paper) a unique and practical tool to investigate water-flooding projects. Basics of the CRM The root of the CRM is the governing material-balance equation stating that the mass difference in an arbitrary control volume (CV) is equal to the mass difference between injected and produced fluid passing through this CV. Then, the governing material-balance equation is combined with a linear productivity model to obtain an ordinary differential equation. The semianalytical solution of the ordinary differential equation forms the CRM. In the field case, there are often many injectors and producers, which would be a large nonlinear optimization problem in the CRM. A CRM-producer (CRMP) model can be used to reduce the number of time constants and increase computational speed. The equations contributing to such a model are provided in the complete paper. Case Study The study area is located in the Parkman reservoir, which is a part of the Powder River Basin in southeast Montana and northeast Wyoming. The Parkman Sandstone Member of the Upper Creta-ceous Mesaverde formation is the oldest sandstone member in a widespread cycle of late Cretaceous regression. The Parkman reservoir consists of multiple stacked sands 5,000 to 9,500 ft deep. There are three dominant lithologies of the Parkman reservoir. The first is pro-delta shale and siltstone, which includes very fine and well-sorted sandstone. The second is medium-grained sandstone, which lies as coarsening-upward successions mixed with siltstone. The last is silt and mudstone, which gradually changes from exhibiting carbonaceous to lignitic characteristics.

Polyurethanes derived from coal extract

ABSTRACTSubbituminous coal from the powder river basin was extracted with N,N‐dimethylformamide at atmospheric pressure to yield a solid extract that provided phenolic and carboxylic acid groups. The coal extract was employed as polyol in polyurethane (PU) synthesis. A solvent‐free synthesis using 2,4‐toluene diisocyanate (TDI) resulted in a porous PU solid. Reaction with TDI in solution resulted in a soluble PU that could be applied as adhesive or coating. Coatings were also prepared from coal extract solutions and commercial, polymeric isocyanates, providing excellent adhesion to aluminum. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48776.

Evaluation of the Umbrella Species Concept at Fine Spatial Scales

ABSTRACTDeclines in the spatial extent of the sagebrush ecosystem have prompted the consideration of conservation efforts that view the greater sage‐grouse (Centrocercus urophasianus; sage‐grouse) as an umbrella species at landscape scales. Conservation strategies that focus on an umbrella species, however, may have unintended negative consequences for co‐occurring species at finer scales. In North America, grassland and shrubland songbird populations are declining faster than other avian groups. Conservation of sage‐grouse habitats may protect songbird habitats where distributions overlap. To assess the umbrella species concept at fine scales, we quantified nest‐site selection for a sagebrush‐obligate songbird, the Brewer's sparrow (Spizella breweri). We then compared the fine‐scale habitat variables that influenced Brewer's sparrow nest‐site selection with fine‐scale nest‐site selection for sage‐grouse in the Powder River Basin region of northeastern Wyoming, USA. We modeled nest‐site selection using conditional logistic regression for Brewer's sparrow (2016–2017) and logistic regression for sage‐grouse (2004–2007). Both species selected nest sites with higher visual obstruction, shrub height, and branching density, although the selection for higher shrub height was stronger for sage‐grouse. Brewer's sparrows selected nest shrubs with higher percentage of living foliage (vigor), and the opposite was shown for sage‐grouse. At the nest site, based on the variables we measured, our results suggest that Brewer's sparrows and sage‐grouse select for similar habitat attributes, with the exception of shrub vigor of the nest shrub. The stronger selection for more vigorous shrubs in Brewer's sparrows may be because they nest in shrubs, rather than on the ground under shrubs (as in sage‐grouse). Most of the conservation objectives for protection of sage‐grouse habitats appear to be beneficial or inconsequential for Brewer's sparrow. Local habitat management for sage‐grouse as a proxy for conservation of other species may be justified if the microhabitat preferences of the species under the umbrella are understood to avoid unintentional negative effects. © 2019 The Wildlife Society.

Enhanced liquid tar production as fuels/chemicals from Powder River Basin coal through CaO catalyzed stepwise degradation in eco-friendly supercritical CO2/ethanol

Developing eco-friendly thermal conversion technologies of coals into fuels/chemicals with minimal environmental impact is highly attractive and significant for efficient coal utilization. CaO catalyzed stepwise degradation at 350–400 °C in eco-friendly supercritical CO2/ethanol (scCO2/ethanol) was carried out to produce high-yield liquid tars as fuels/chemicals from Powder River Basin (PRB) coal. The total yield of the liquid tars increased from 53.9 wt% for non-catalytic stepwise degradation to 60.1 wt% for CaO catalyzed stepwise degradation, with an increase of 6.2 wt%. The resulting ash-free liquid tars are promising raw materials as clean liquid fuels for energy production due to their high H/C ratio (1.16–1.88) and heating values (32.84–35.84 MJ/kg). Compared with non-catalytic stepwise degradation, the energy recovery increases from 62.8% to 71.6% by CaO catalyzed stepwise degradation. More than 75% of the components in the liquid tars were volatilized and/or degraded at temperature <500 °C according to thermogravimetric analysis. The distributions of the functional groups and group components in the liquid tars are similar to each other. Phenols are the most abundant volatile group component in the liquid tars, accounting for about 43% of the volatile components released at 350 °C and 375 °C by CaO catalyzed stepwise degradation. The CaO promoted forming active H+ and CH3CH2O− from ethanol, which readily attacked and cleaved weak -C-O- bonds in the PRB coal, leading to producing more phenols and arenes. Thermal dissociation of the non-covalent interactions especially hydrogen bonds or the cleavage of weak -C-O- in PRB coal could interpret the generation of phenols.

Low temperature heating and oxidation to prevent spontaneous combustion using Powder River Basin coal

Powder River Basin coal, a subbituminous coal, was studied for its low temperature oxidation tendency after a simple surface oxidation treatment. The influence of the heating temperature on the coal properties was studied. The tendency of this dried coal to oxidize at low temperatures was successfully eliminated by lightly oxidizing the coal in the air at 100 to 200 ºC. The surface reactions during the process were also studied. We found that the passivation treatment appears to consume the functional groups that are prone to low temperature oxidation, such as aliphatics. The passivation effect was weakened when the oxidation temperature went above 200 °C, as decomposition happens. The oxidation reactions are monitored through two different methods: analyzing the CO2 and water produced using quadrupole mass spectrometry (QMS) and analyzing the heat release at oxidation using the differential scanning calorimetry (DSC). Gas chromatography–mass spectrometry (GC-MS) was used to analyze the coal tar material produced from low temperature heating. Scanning electron microscopy (SEM), Surface area measurements, and Fourier Transform Infrared Spectroscopy (FTIR) are used for surface characterization of the solids.

Carbon mass balance, isotopic tracers of biogenic methane, and the role of acetate in coal beds: Powder River Basin (USA)

A multi-isotope (C, H, O) investigation of biogenic gas (δ13C−CH4, δ13C−CO2, δD−CH4) and coal bed waters (δD, δ18O, δ13C-DIC, δ13C-acetate) was conducted along a ∼25-km basinward sampling transect in the Powder River Basin (PRB) in Wyoming and Montana (USA) to address inconsistencies among isotope fingerprinting techniques and to apply mass balance isotope modeling to biogenic coalbed methane (CBM). Results include the first published compound-specific δ13C-acetate values from a natural biogenic CBM system, providing new constraints on acetate’s role in biogenic CH4 generation. Coal bed water chemistry is anoxic and dominated by Na+ and HCO3−, with high alkalinity concentrations (14.8–33.0meq/L). The deep basin interior environment contains sulfate-free, Na+−HCO3−-dominated waters exhibiting signs of methanogenesis. CH4 and CO2 generally become 13C-enriched from the shallow basin edge to the deep basin interior (δ13C−CH4 −78.2 to −56.2‰ and δ13C−CO2 -24.7 to 4.7‰). Also, compound-specific δ13C-acetate is more positive in the basin interior compared to the basin edge setting (range −34.3 to −15.1‰). Using a steady-state mass balance isotope model, the observed variations in δ13C-CH4 and δ13C-CO2 can be explained in terms of the favorability of methanogenesis (fCH4) relative to heterotrophic bacterially-mediated non-methanogenic pathways, such as bacterial sulfate reduction, which compete with methanogenesis for substrates. At the basin interior, fCH4 exceeds 0.4, approaching its inferred limiting value hypothesized from the oxidation state of low-molecular weight compounds detected in PRB formation waters. Therefore, methanogenesis is likely a dominant biogeochemical pathway consuming substrates in the deeper coal beds. The basinward shift toward 13C-enriched acetate broadly indicates linkage between acetate, CH4, and CO2, and likely records acetate synthesis effects modified by methanogenic fractionation. These results suggest that acetate plays a role in methanogenesis in PRB coal beds (not necessarily a dominant role), while other C isotope and microbial evidence suggests that hydrogenotrophic methanogenesis is also a significant methane-producing pathway. The results of this study broadly suggest multiple viable methanogenic pathways and C cycling that affects acetate, a more complex view of coal bed geochemistry than implied by traditional C and H isotope fingerprinting of accumulated products (CH4, CO2) and coexisting water.

Kinetics and mechanism of CO2 gasification of coal catalyzed by Na2CO3, FeCO3 and Na2CO3–FeCO3

The purpose is to develop a mild catalytic CO2-gasification technology that can promote CO2 utilization and reduce cost in air separation systems with improving system efficiency and obtaining desirable gaseous products. In this study, the influence of Na, Fe and their composite catalysts on the structure and gasification reactivity of chars derived from pyrolysis of Powder River Basin (PRB) coal was investigated. The results showed that a strong positive synergistic effect between Na and Fe catalyst in the gasification process was observed, the catalytic activity of the added catalysts was in order of: 4% Na > 3% Na–1%Fe > 2% Na-2% Fe > 1% Na-3% Fe > 1% Na-2% Fe > 4% Fe > raw coal. The catalysts inhibited the growth of the aromatic ring structure and enriched the generation of O-containing functional groups. Compared to Fe, the Na-based catalyst could easily diffuse into inner pores of coal char, forming C–O–Na structure and thus increasing the gasification reactivity of chars. In addition, due to the formation of inert material between SiO2 and Na, the catalytic activity of Na catalysts was significantly decrease at the late stage of char conversion. Comparatively, the Fe-based catalysts showed better stability life. Moreover, it was found that the activation energy for CO2-gasification of PRB coal can be decreased by 50% due to the addition of Na catalyst.

Rare earth elements of fly ash from Wyoming's Powder River Basin coal

The advancement and increasing interests in green energy production and environmental protection technologies have spurred the demand for rare earth elements. On the other hand, the U.S. has to rely 100% on import of these materials as the industry was crashed because of the environmental issues associated with mining and processing, and more importantly lack competitiveness. As rare earth elements have many applications in defense and national security sectors, some of the elements were listed as strategic materials or critical materials because of the uncertainties in supply and prices. Therefore, it has become imperative in searching for alternative resources for supplying rare earth elements including unconventional resources. With the strong incentive, coal fly ash is identified as one of the candidates among them. In this study, we present rare earth element data for the 42 ash samples (all derived from Powder River Basin coal) that we collected from seven states (UT, WY, IO, WI, ND, CO, and MI) representing 158 million tons of fly ash. The results indicate scattered distributions of rare earth elements with concentration ranging from 156 to 590 ppm although all the ash samples originated from the same coal basin (Powder River Basin). The rare earth element resource in these ashes is estimated between 74000 and 106000 t. The ash samples were also characterized by elemental analysis, XRD, SEM-EDS and BET surface area. The characterizations of the ashes were discussed as they might have implications in the subsequent rare earth element extraction processes. In summary, fly ash may represent a potential resource for rare earth element production.

Improved gasification efficiency in IGCC plants & viscosity reduction of liquid fuels and solid fuel dispersion using liquid and gaseous CO2

The applications of liquid CO2 as a slurry fluid for solid carbon feedstock (coal and biomass sludge) and impacts on gasification performance have been investigated experimentally and analytically. CO2 for rheological control of solid fuel suspensions resulted in solids loading of nearly 66 weight% (wt%) closely matching the theoretical loading of 68 wt%. As a representative example, the measured viscosity for Illinois #6 coal slurry was found to be between 31 and 87 mPa-s using CO2 compared to 62–300 mPa-s using water for loadings between 50 and 66 wt% solids, respectively. Similarly, a viscosity reduction of nearly a factor of four was measured for a heavy oil sample from the Utica basin. The viscosity of the oil at 40 °C and 100 psi measured 10.25 Pa.s yet a 0.64 wt% CO2 yielded a viscosity of 2.42 Pa-s. The gasification performance investigation was done using ASPEN® Plus simulations to understand the impact of CO2 on Integrated Gasification Combined Cycle (IGCC) plant and the gasifier performance. The results show that co-feeding CO2 into the gasifier provides higher cold gas efficiency (CGE). The baseline cold gas efficiency using steam gasification (no CO2) of Powder River Basin (PRB) coal is 78.46% whereas two cases in which CO2 was added provided CGE values of 83.22 and 81.13%. These simulations were validated via a series of Drop Tube Reactor experiments and show good agreement. The carbon conversion during gasification at 1000 ℃ increased from ∼50% to ∼68% by addition of 30% CO2.

Preliminary detrital zircon U-Pb Geochronology of the Wasatch Formation, Powder River Basin, Wyoming

The lower Eocene Wasatch Formation is more than 1500 m thick in the Powder River Basin of Wyoming. The Wasatch is a Laramide synorgenic deposit that consists of paludal and lacustrine mudstone, fluvial sandstone, and coal. U-Pb geochronologic data on detrital zircons were gathered for a sandstone unit in the middle part of the succession. The Wasatch was collected along Interstate 90 just west of the Powder River, which is about 50 km east of the Bighorn Mountain front. The sandstone is lenticular in geometry and consists of arkosic arenite and wacke. The detrital zircon age spectrum ranged (n=99) from 1433-2957 Ma in age, and consisted of more than 95% Archean age grains, with an age peak of about 2900 Ma. Three populations of Archean ages are evident: 2886.6±10 Ma (24%), 2906.6±8.4 Ma (56%) and 2934.1±6.6 Ma (20%; all results 2 sigma). These ages are consistent with the age of Archean rocks exposed in the northern part of the range. The sparse Proterozoic grains were likely derived from the recycling of Cambrian and Carboniferous strata. These sands were transported to the Powder River Basin through the alluvial fans adjacent to the Piney Creek thrust. Drainage continued to the north through the basin and eventually into the Ancestral Missouri River and Gulf of Mexico. The provenance of the Wasatch is distinct from coeval Tatman and Willwood strata in the Bighorn and Absaroka basins, which were derived from distal source (&gt;500 km) areas in the Sevier Highlands of Idaho and the Laramide Beartooth and Tobacco Root uplifts. Why the Bighorn Mountains shed abundant Eocene strata only to the east and not to the west remains enigmatic, and merits further study.

Detrital zircon U-Pb geochronology of the Ordovician Lander Sandstone, Bighorn Mountains, Wyoming

The Ordovician Lander Sandstone, which occurs unconformably above the Cambrian Gallatin Limestone and beneath the Bighorn Dolomite, occurs in the Bighorn, Powder, and Wind River basins of Wyoming. The Lander ranges from 0-10 m in thickness and consists of texturally and compositional mature, cross bedded quartz arenite. This study uses detrital zircon U-Pb geochronology to elucidate its provenance. Samples were collected from two localities along the eastern flank of the Bighorn Mountains near Buffalo, Wyoming: a roadcut on US 16 just west of the Clear Creek thrust and from along Crazy Woman Canyon Road. The results showed a statistical similarity between the two samples, and that zircon ages are predominantly Proterozoic in age (~75%) while the minority ages were Archean (25%). Probability density plots of the two-source areas show that the peak ages for Crazy Woman Canyon (n=90) are ~1840, 2075 and 2695 Ma and the US 16 peak ages (n=141) are ~1825, 2075, and 2725 Ma. The detrital zircon age spectra for these samples indicate that the Lander was not derived from local Archean basement and was not recycled from the underlying Cambrian. The Lander has a provenance in either the Trans-Hudson Province and adjacent rocks in present day Saskatchewan and Manitoba more than 1000 km to the north or from the Peace River Arch, an early Paleozoic highlands in northwestern Alberta and northeastern British Columbia. The Lander zircons have a similar provenance to eolian zircons in the Bighorn Dolomite and to other Ordovician sandstones on the Cordilleran Continental margin and central Idaho. The Lander provenance is distinct from the Ordovician St. Peter Sandstone, which occurs extensively east of the Transcontinental Arch. We interpret that the Lander was derived on the late Ordovician shoreline, and then transported via prevailing winds across the Laurentian shelf from east to west during sea level low stand, and then distributed throughout the shelf by currents.

Detrital Zircon U-Pb geochronology of the Ordovician Lander Sandstone, Bighorn

The Ordovician Lander Sandstone, which occurs unconformably above the Cambrian Gallatin Limestone and beneath the Bighorn Dolomite, occurs in the Bighorn, Powder, and Wind River basins of Wyoming. The Lander ranges from 0-10 m in thickness and consists of texturally and compositional mature, cross bedded quartz arenite. This study uses detrital zircon U-Pb geochronology to elucidate its provenance. Samples were collected from two localities along the eastern flank of the Bighorn Mountains near Buffalo, Wyoming: a roadcut on US 16 just west of the Clear Creek thrust and from along Crazy Woman Canyon Road. The results showed a statistical similarity between the two samples, and that zircon ages are predominantly Proterozoic in age (~75%) while the minority ages were Archean (25%). Probability density plots of the two-source areas show that the peak ages for Crazy Woman Canyon (n=90) are ~1840, 2075 and 2695 Ma and the US 16 peak ages (n=141) are ~1825, 2075, and 2725 Ma. The detrital zircon age spectra for these samples indicate that the Lander was not derived from local Archean basement and was not recycled from the underlying Cambrian. The Lander has a provenance in either the Trans-Hudson Province and adjacent rocks in present day Saskatchewan and Manitoba more than 1000 km to the north or from the Peace River Arch, an early Paleozoic highlands in northwestern Alberta and northeastern British Columbia. The Lander zircons have a similar provenance to eolian zircons in the Bighorn Dolomite and to other Ordovician sandstones on the Cordilleran Continental margin and central Idaho. The Lander provenance is distinct from the Ordovician St. Peter Sandstone, which occurs extensively east of the Transcontinental Arch. We interpret that the Lander was derived on the late Ordovician shoreline, and then transported via prevailing winds across the Laurentian shelf from east to west during sea level low stand, and then distributed throughout the shelf by currents.

Detrital Zircon U-Pb Geochronology and Provenance of the Sundance Formation, Western Powder River Basin, Wyoming

This study uses detrital zircon U-Pb geochronology to investigate the provenance of the Jurassic Sundance Formation in the western Powder River Basin, Wyoming. Understanding the provenance of the Sundance Formation is critical as it was deposited during the transition from cratonic to synorogenic sedimentation derived from the Sevier-Laramide foreland. The Sundance in the western Powder River Basin consists of an oolitic limestone and green glauconitic sandstone at the base, green shales in the middle, and a yellow quartz arenite with coquina “oyster” beds at the top. U-Pb analyses of detrital zircons using LA-ICP-MS were conducted on two samples collected in the Bud Love Wildlife Habitat Management Area, 20 km northwest of Buffalo, WY. The two samples were taken from the upper and lower sandstone members of the Sundance Formation (n=289 concordant U-Pb zircon ages). The samples show a distinct difference in detrital zircon age spectra. The lower sandstone age spectrum ranges from 260-3172 Ma with 23% of the ages being Paleozoic, 71% being Proterozoic, and 6% being Archean. This lower stratum has detrital zircon age peaks at 343, 432, 686, 1039, 1431, 1662, 1748, 1941, 2433, and 3179 Ma. The lower sandstone shows an easterly Appalachian-Ouachita provenance, which persisted in the region beginning in the Carboniferous. In comparison to the upper strata, ages range from 157-2949 Ma and age peaks at 170, 243, 440, 545, 1082, 1467, 1681, and 1985 Ma. The maximum deposition age for the upper member is 160 Ma. Mesozoic aged grains make up 15.6% of the zircons, 14.7% were Paleozoic, 65.7% were Proterozoic, and 4% were Archean in age. The appearance of Mesozoic zircons in the upper sandstone marks the first significant appearance of westerly sourced zircons, and perhaps reflects the earliest uplift of the Sevier fold and thrust belt. Previous research has found this same signature in the Sundance but not in the underlying Triassic Chugwater Formation, resulting in a broad boundary of the change in sediment dispersal and the onset of the Sevier Orogeny between the Triassic and Jurassic. This study was conducted for a higher resolution to the provenance of the Sundance Formation and to further narrow the boundary of differing sedimentation from an eastern recycled to western synorogenic source.