Green River Research Articles

Investigating fracture propagation characteristics in shale using sc-CO2 and water with the aid of X-ray Computed Tomography

The further development of unconventional resources is anticipated to increase the intensity of hydraulic fracturing operations. Injecting water-based fracturing fluids into shale formations, especially shales producing gas, may have adverse impacts of water blocking, scale formation, and water-sensitive clay minerals. Accordingly, nonaqueous candidates such as carbon dioxide (CO2) need to be explored to avoid injection of millions of gallons of water and to increase the effectiveness of stimulation jobs. This study investigates fracturing behavior accompanying supercritical carbon dioxide (sc-CO2) injection compared to water. A High Pressure High Temperature (HPHT) triaxial cell was utilized to conduct shale breakdown experiments under reservoir-like conditions. Furthermore, the experimental setup allows continuous monitoring of in situ details using X-ray Computed Tomography (CT). Here, CT images were utilized for the first time to investigate and confirm the breakdown pressure using Fast Iterative Digital Volume Correlation (FIDVC) that permits visualization of in situ deformation and strain. One inch diameter Green River shale samples were fractured under triaxial stress conditions. Results demonstrated a roughly 2 to 3 times greater breakdown pressure for sc-CO2 compared to water for the samples studied. Compressive infiltration stress might explain such behavior, and mineralogy is believed to be a major contributor to such differences between injectants. Under isotropic horizontal stresses, sc-CO2 induces fractures propagating almost independent of bedding planes. This is a promising finding for probable larger stimulated volume achieved by sc-CO2. CT imaging to monitor fracture propagation demonstrated excellent performance in detecting fracture propagation. We anticipate this technique to help significantly when monitoring fracture propagation mechanisms for laboratory samples with slow pressurization as well as studies of slip on pre-existing fractures.

Organic petrology and geochemistry of Lower Cretaceous lacustrine sediments in the Chaoyang Basin (Liaoning Province, northeast China): Influence of volcanic ash on algal productivity and oil shale formation

Airfall volcanic ash deposited in the form of tuff layers is widely distributed in oil-shale bearing basins in western Liaoning Province, northeast China. In order to investigate the impacts of volcanic ash on algal productivity and the formation of organic-rich oil shales, the organic petrology and organic geochemistry of lacustrine sediments of the Lower Cretaceous Jiufotang Formation were investigated. Molecular geochemical data (the pristane/phytane ratio, the gammacerane index and the relative amount of β-carotane) indicate that they were formed in suboxic/anoxic depositional environments, with salinity fluctuations from freshwater to saline. Oil shales in the semi-deep to deepwater lake facies were mainly deposited under still and anoxic bottom water conditions, concomitant with water column salinity stratification. The relative abundances of diterpenoids and regular steranes indicate a limited terrigenous conifer plant contribution and a predominantly algal contribution to the organic matter. Blooms of algae contributing to high primary productivity, and anoxic depositional environments contributing to organic matter preservation, were key to organic-rich oil shale formation. Fish bones, ostracod shells, and alginite are present below the thick tuff layer. Alginite richness gradually increased from very low just above the tuff layer, to a higher concentration further above the tuff layer, indicating that during major volcanic eruptions, large quantities of volcanic ash led to water column poisoning, causing the sudden mass mortality of some aquatic organisms that were sensitive to turbid, acidified and toxic water. The increased proportion of brackish/saline-water dinoflagellates, which is corroborated by the high concentration of telalginite, abundant dinoflagellate-specific biomarkers (C31 4,22,23,24-tetramethylcholestanes), high values of the C27/C29 ααα-20R and C28/C29 ααα-20R sterane ratios, 4-methylsterane index, dinosterane index, and tetramethylsterane index, suggest that brackish/saline-water dinoflagellates show a positive response to volcanic ash input. Some specific brackish/saline-water dinoflagellates are present in organic-rich tuff laminae, indicating that during periods of minor volcanic eruptions or in intermissions between major eruptions, a minor volcanic ash input was more likely to result in rapid and efficient volcanic fertilisation effects and high-quality oil shale formation. Although the lacustrine oil shale system of the Jiufotang Formation shares some similar petrological and geochemical characteristics with the classical saline lacustrine oil shale system of the Green River Formation in the United States of America, the significant influence of airfall volcanic ash on algal productivity makes the formation mechanism of oil shales within the Jiufotang Formation strata quite different from that of oil shales within the Green River Formation.

Light Trap Effectiveness to Capture Razorback Sucker Larvae in a Large Floodplain Wetland

AbstractLight trap captures of larval Razorback Sucker Xyrauchen texanus are used to trigger flow releases from Flaming Gorge Reservoir, which inundate floodplain wetland nursery habitat in the Green River, Utah. However, because little is known about the efficacy of traps to capture or retain larvae under field‐relevant conditions, we conducted an exploratory study using releases of unmarked and marked (oxytetracycline hydrochloride) early life stages of Razorback Sucker (mesolarval life stage, hereafter called “larvae”) in the 53‐ha Leota‐10 wetland of the middle Green River. Batches of 10, 50, 250, or 1,000 larvae were released 3‐ or 10‐m from light traps. Light traps had either chemical light stick or LED light sources, and releases were made on two successive evenings to assess recapture proportions. Light traps recaptured larvae each night and at all release abundances in this large and open habitat. Recapture proportions (number recaptured per number released) for individual traps ranged from 0 to 0.68 (mean = 0.11) over the two release nights. Because recapture proportions were similar over all release abundances, light trap captures may be an index of larvae abundance. In addition, recapture proportions of larvae in traps (light sources combined) were not influenced by release distance. Nonsignificant tests for release distance and release abundance effects had low statistical power resulting from high sample variability and modest sample sizes, so additional experiments are required to confirm those results. The ANCOVA also indicated that traps with an LED light source had consistently higher recapture proportions than traps lit with chemical light sticks, in support of laboratory findings. Although additional experiments with greater replication are needed to better understand attraction distance, release abundance, and retention effects, light traps may be a useful tool to monitor presence and abundance of larvae. This information will aid management and conservation of endangered Razorback Sucker in the Colorado River basin.

The damselfly palaeofauna from the Eocene of Wyoming and Colorado, USA (Insecta, Odonata, Zygoptera)

AbstractA new family, five new genera, and nine new species of fossil damselflies (Insecta, Odonata, Zygoptera, Calopterygida) from the USA are described, seven from the Eocene Fossil Lake deposits and one from Lake Uinta deposits, both from the Green River Formation, and an additional specimen from the Wind River Formation of Wyoming and Colorado. Namely, Carlea eocenica gen. et sp. nov. (in Carleidae fam. nov.), Labandeiraia riveri sp. nov., Labandeiraia browni sp. nov., Eodysphaea magnifica gen. et sp. nov., Litheuphaea sp. cf. coloradensis Petrulevičius et al., 2007, Zacallites cockerelli sp. nov., Dysagrion integrum sp. nov., Tenebragrion shermani gen. et sp. nov., Tynskysagrion brookeae gen. et sp. nov., and Oreodysagrion tenebris gen. et sp. nov. Epallagoidea and Amphipterygoidea are most common while Calopterygoidea, Coenagrionoidae and Lestoidea damselflies are less diverse. Genera of zygopteran Dysagrionidae are known from Europe and North America, further supporting the hypothesis of Palaeogene terrestrial interchange. Representatives of Epallagoidea and Amphipterygoidea in the Green River Formation confirm that warm conditions occurred at the time of deposition.

Lake basin closure and episodic inflow as recorded by radiogenic Sr isotopes: Eocene Green River Formation in the Piceance Creek Basin, Colorado

Lacustrine basins are excellent archives of lake evolution, and deposits record the uplift and weathering histories of the surrounding terrain. The application of Sr isotopes has been tested in several lacustrine basins, both modern and ancient, based on the premise that lakes are well mixed, and shifting Sr isotopes may suggest changes in lake provenance. In the Eocene lacustrine Green River Formation in the Piceance Creek Basin of Colorado, Sr isotope analysis of carbonate mudstones indicates that radiogenic Sr in the center of the Piceance lake decreased during the evolution of the lake, from 52.8–48.4 Ma. Because deposition in the basin center occurred away from the influence of episodic alluvial inflow at the basin margin, Sr isotope evolution in the Piceance lake after basin closure is recorded in the John Savage #24-1 core deposits, not the Anvil Points deposits. Sr isotope analysis of carbonate mudstones at Anvil Points below 55 m shows fluctuating radiogenic Sr values that record episodic inflow from the White River Uplift. This inflow is responsible for the difference in radiogenic Sr trends recorded between the basin center and margin. Above 55 m, fluctuating Sr isotope values at Anvil Points record episodic inflow from the White River Uplift, without inflow of Paleozoic and Mesozoic carbonates. The boundary at 55 m records the hydrologic closure of the Uinta and Piceance lakes around 52 Ma, when lake level lowered beneath the basin sill and the lakes were no longer connected across the Douglas Creek Arch. A significant increase in radiogenic Sr across the 55-m-boundary records this transition from open to closed hydrology, reflecting a loss of dissolved Sr sourced from Paleozoic and Mesozoic carbonates.

Does Channel Narrowing by Floodplain Growth Necessarily Indicate Sediment Surplus? Lessons From Sediment Transport Analyses in the Green and Colorado Rivers, Canyonlands, Utah

AbstractAnalyses of suspended sediment transport provide valuable insight into the role that sediment supply plays in causing geomorphic change. The sediment supply within a river system evolves depending on the discharge, flood frequency and duration, changes in sediment input, and ecohydraulic conditions that modify sediment transport processes. Changes in supply can be evaluated through analyses of coupled changes in suspended sediment concentration and grain size. The concentration of sand in transport in the Green and Colorado Rivers is most strongly controlled by discharge and the bed sand grain size distribution. Since the 1950s, sand loads have decreased in response to declines in peak discharge in the Green River and coarsening of the bed sand in the Colorado River. However, changes in the bed sand grain size distribution are associated with large changes in suspended sand concentration in both rivers; concentration varies by a factor of ~3 in the Green River and a factor of ~8 in the Colorado River, depending on the bed sand grain size distribution. Analyses of hysteresis in suspended sediment measurements show that sediment depletion during annual floods is most strongly controlled by flood duration, with peak discharge being nearly equally important in the Green River. Despite channel narrowing in both rivers, periods of bed sand coarsening and sediment depletion during annual floods indicate that these rivers are not necessarily in sediment surplus. Channel narrowing appears to be strongly controlled by short‐term declines in flood magnitude and the ecohydraulic effects of vegetation and may not be indicative of the long‐term sediment budget.

An Exceptionally Preserved Specimen From the Green River Formation Elucidates Complex Phenotypic Evolution in Gruiformes and Charadriiformes

The stem lineage relationships and early phenotypic evolution of Charadriiformes (shorebirds) and Gruiformes (rails, cranes, and allies) remain unresolved. It is still debated whether these clades are sister-taxa. New phylogenetic analyses incorporating Paleogene fossils have the potential to reveal the evolutionary connections of these two speciose and evolutionarily critical neoavian subclades. Although Gruiformes have a rich Paleogene fossil record, most of these fossils have not been robustly placed. The Paleogene fossil record of Charadriiformes is scarce and largely consists of fragmentary single elements. Only one proposed Eocene charadriiform-like taxon,Scandiavis mikkelseniof Denmark, is represented by a partial skeleton. Here, we describe a new species from the early Eocene Green River Formation of North America comprising a partial skeleton and feather remains. Because the skeleton lacks the pectoral girdle and forelimbs as inS. mikkelseni, only features of the skull, axial skeleton, and hind limb are available to resolve the phylogenetic placement of this taxon. These anatomical subregions initially showed features seen in Charadriiformes and Gruiformes. To assess placement of this taxon, we use a matrix consisting of 693 morphological characters and 60 taxa, includingS. mikkelseniand the oldest known charadriiform taxa represented by single elements. These more fragmentary records comprise two distal humeri from the earliest Eocene Naranbulag Formation of Mongolia and the early Eocene Nanjemoy Formation of Virginia. Our phylogenetic analyses recover the new taxon andS. mikkelsenialternatively as a charadriiform or as a stem-gruiform; placement is contingent upon enforced relationships for major neoavian subclades recovered by recent molecular-based phylogenies. Specifically, when constraint trees based on results that do not recover Charadriiformes and Gruiformes as sister-taxa are used, the new taxon andS. mikkelseniare recovered within stem Gruiformes. Both Paleogene fossil humeri are consistently recovered within crown Charadriiformes. If placement of these humeri or the new taxon as charadriiforms are correct, this may indicate that recent divergence time analyses have underestimated the crown age of another major crown avian subclade; however, more complete sampling of these taxa is necessary, especially of more complete specimens with pectoral elements.

Effective anaerobic treatment of produced water from petroleum production using an anaerobic digestion inoculum from a brewery wastewater treatment facility

Produced water is a major waste problem in oil production yet it also represents a potential water source if treated properly, especially in arid regions. In this study, we investigate the anaerobic treatability of an oil-produced water with extremely high chemical oxygen demand (COD) and total dissolved organic carbon (TOC) from Wyoming’s Greater Green River Basin using anaerobic microcosms inoculated with a microbial consortium derived from a brewery wastewater treatment facility. The results demonstrate that for this water and an appropriate microbial inoculation, high-COD/TOC can be effectively removed with concomitant energy recovery as a form of methane. 93% and 89% of the COD and TOC were removed with a final high methane yield of 33.9 mmol/g carbon (848 μmol/g carbon/day). Chemical analyses showed that the ethylacetate-extractable compounds were much more amenable to biodegradation than the CH2Cl2 extractable compounds. Furthermore, compounds that were added during drilling and completion remained in the water and contributed significantly to the COD and anaerobic degradability. This study demonstrates that produced waters are amenable to anaerobic biological treatment and also that thorough chemical analyses are necessary to fully understand the potential for treatment.

Application of Digital Volume Correlation to X-ray Computed Tomography Images of Shale

We investigated the Young’s modulus and Poisson’s ratio of Green River oil shale at elevated temperatures under triaxial conditions using an X-ray computed tomography (CT) scanner for in situ imaging, fast iterative digital volume correlation (FIDVC) for visualization of displacement and volumetric strain patterns, and a conventional linear variable differential transducer (LVDT) to measure the displacement independently. FIDVC was applied to time-lapse CT images to visualize the distribution of axial normalized displacement (Uz) and volumetric strain (εV) within the samples at the resolution of the CT images. Importantly, the displacement obtained by FIDVC was calibrated and verified with LVDT measurements. Both axial normalized displacement (Uz) and volumetric strain (εV) profiles from the FIDVC method present the location of greater strains within samples including layered material of greater density and lesser density organic matter (kerogen and bitumen) rich zones. The Young’s modulus remained unchanged upon heating to around 200 °C, but decreased following kerogen maturation at 350 °C. Young’s modulus decreased at 350 °C due to rock softening and conversion (maturation) of kerogen to oil or gas. Accordingly, the fraction of kerogen in a sample plays a critical role on Young’s modulus. These observations agree with trends found in the literature (White et al., 2017; Burnham, 2018), but without in situ imaging. Similarly, Poisson’s ratio did not change after pyrolysis but increased post maturation.

Simultaneous enantiomeric analysis of five proton-pump inhibitors in soil and sediment using a modified QuEChERS method and chiral high performance liquid chromatography coupled with tandem mass spectrometry

This study presents a simple, sensitive, rapid, cheap and reliable method for the simultaneous quantification of five proton pump inhibitors (omeprazole, rabeprazole, lansoprazole, pantoprazole, and ilaprazole) at enantiomeric levels in environmental soil and river sediment by chiral high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The modified QuEChERS procedure, a very simple and efficient sample preparation method, was employed for the extraction and purification of the target analytes. To obtain satisfactory chromatographic performance and high extraction efficiency, several experimental variable parameters including the type and content of the organic modifier, the content of the additive, temperature and mobile phase flow rate, the type and volume of extraction solvent, and the type and content of clean-up sorbent were systematically optimized. Under the optimum condition, the simultaneous baseline separation of five chiral drugs was achieved on a Chiralpak IH column within 13 min. The method detection limits and quantification limits of the enantiomers were below 0.17 ng/g and 0.69 ng/g, respectively. Correlation coefficients (R2) ≥ 0.9905 were obtained for all enantiomers within the linearity range of 1–200 ng/g. The mean recoveries for all enantiomers ranged from 83.6% to 108.5% with intra-day RSD less than 11.6% and inter-day RSD less than 12.9%. Finally, the proposed method was successfully applied to authentic samples (green belt soil, agricultural soil, and river sediment) to analyze the enantiomeric composition of target chiral analytes, indicating its applicability and reliability for the enantioselective determination of proton pump inhibitors in environmental matrices. This research will help better elucidate the behavior of individual enantiomer and make an excellent risk assessment on the environment.

Groundwater mixing in an alkaline paleolake: Eocene Green River Formation, Wyoming

Tufa in the Little Mesa area of the northern Bridger Basin has been interpreted to record carbonate deposition via subaqueous and subaerial springs emanating near the shoreline of Eocene Lake Gosiute. Sedimentary facies record an overall transgression, culminating with mound structures that reach up to 9 m in height and 40 m in diameter. Mounds exhibit a strong positive, linear covariance between δ13C and δ18O, defining a slope of ~1. Similar trends occur in many other paleolake deposits, where they are interpreted to reflect changes in evaporation, atmospheric CO2 exchange, and organic matter burial. However, δ13C and δ18O in this study also covary strongly with 87Sr/86Sr, a new finding that is inconsistent with previously proposed mechanisms. We conclude that Little Mesa isotopic trends reflect mixing of groundwater with low 87Sr/86Sr, δ18O and δ13C and lake water with opposite characteristics. Low 87Sr/86Sr in groundwater likely resulted from interaction with marine carbonate strata within the Sevier fold and thrust belt to the west, whereas drainage from Precambrian-cored uplifts that bounded Lake Gosiute to the north, east, and south was responsible for higher lake water ratios.Little Mesa carbonate facies are all less radiogenic than any time-equivalent facies near the center of the basin, implying horizontal and vertical gradients in Lake Gosiute 87Sr/86Sr. Previous studies have shown that the lowest 87Sr/86Sr in basin center deposits correspond to lake highstands. Results of this study support the hypothesis that climatic modulation of surface runoff and spring emanations from the Sevier belt were principally responsible for precessional-scale expansions and contractions of Lake Gosiute. More broadly, groundwater discharge may represent an important but underappreciated contributor to covariance between 87Sr/86Sr ratios, δ13C and δ18O in closed paleolake systems.

Astronomical Observations of the 1869 Powell Expedition Through the Grand Canyon

During his 1869 expedition down the Green River and through the Grand Canyon, Major John Powell made astronomical observations using a sextant and artificial horizon to fix the locations of key points along the rivers that were only poorly known at the time. Latitude was obtained from the altitude of Polaris or meridian transits of stars or Saturn. Local mean time was determined from equal altitude observations of the Sun. The swamping of one of the expedition's small boats ruined the chronometers, meaning that they could not be used to keep Greenwich mean time and hence find longitude. As a substitute a series of lunar distance observations were undertaken. In this paper observations recorded in Powell's journal are reduced and analysed.

The role of hydrothermal fluids in sedimentation in saline alkaline lakes: Evidence from Nasikie Engida, Kenya Rift Valley

AbstractSaline alkaline lakes that precipitate sodium carbonate evaporites are most common in volcanic terrains in semi‐arid environments. Processes that lead to trona precipitation are poorly understood compared to those in sulphate‐dominated and chloride‐dominated lake brines. Nasikie Engida (Little Magadi) in the southern Kenya Rift shows the initial stages of soda evaporite formation. This small shallow (<2 m deep; 7 km long) lake is recharged by alkaline hot springs and seasonal runoff but unlike neighbouring Lake Magadi is perennial. This study aims to understand modern sedimentary and geochemical processes in Nasikie Engida and to assess the importance of geothermal fluids in evaporite formation. Perennial hot‐spring inflow waters along the northern shoreline evaporate and become saturated with respect to nahcolite and trona, which precipitate in the southern part of the lake, up to 6 km from the hot springs. Nahcolite (NaHCO3) forms bladed crystals that nucleate on the lake floor. Trona (Na2CO3·NaHCO3·2H2O) precipitates from more concentrated brines as rafts and as bottom‐nucleated shrubs of acicular crystals that coalesce laterally to form bedded trona. Many processes modify the fluid composition as it evolves. Silica is removed as gels and by early diagenetic reactions and diatoms. Sulphate is depleted by bacterial reduction. Potassium and chloride, of moderate concentration, remain conservative in the brine. Clastic sedimentation is relatively minor because of the predominant hydrothermal inflow. Nahcolite precipitates when and where pCO2 is high, notably near sublacustrine spring discharge. Results from Nasikie Engida show that hot spring discharge has maintained the lake for at least 2 kyr, and that the evaporite formation is strongly influenced by local discharge of carbon dioxide. Brine evolution and evaporite deposition at Nasikie Engida help to explain conditions under which ancient sodium carbonate evaporites formed, including those in other East African rift basins, the Eocene Green River Formation (western USA), and elsewhere.

The roles of flood magnitude and duration in controlling channel width and complexity on the Green River in Canyonlands, Utah, USA

Predictions of river channel adjustment to changes in streamflow regime based on relations between mean channel characteristics and mean flood magnitude can be useful to evaluate average channel response. However, because these relations assume equilibrium sediment transport, their applicability to cases where streamflow and sediment transport are decoupled may be limited. These general relations also lack the specificity that is required to connect specific characteristics of the streamflow and sediment regime with the dynamics of channel morphological change that create channel complexity, which is often of ecological interest. We integrate historical records of channel change, observations of scour and fill during a snowmelt flood, measurements of sediment transport, and predictions from a two-dimensional streamflow model to describe how annual peak flow magnitude and peak-flow duration interact with the upstream sediment supply to control channel form for a 15-km study reach on the regulated Green River in Canyonlands National Park, Utah. Two major decadal-scale episodes of channel narrowing have occurred within the study area. For each of these episodes, the reduction in average channel width was consistent with the change predicted by hydraulic geometry relations as a function of average flood magnitude. However, channel narrowing occurred during periods of exceptionally low annual floods. The most recent episode of channel narrowing occurred between 1988 and 2009, during low-flow cycles when the 5-yr mean peak flow was less than 60% of the long-term (1959–2016) mean peak flow. These findings, together with findings from previous studies, demonstrate that decreases in peak-flow magnitude caused by streamflow regulation, climate change, or a combination of those factors have driven episodes of channel narrowing on the Green River. Observations of streamflow, sediment-transport, and morphologic change coupled with predictions from a two-dimensional streamflow model indicate that peak flow magnitudes of at least 75% of the long-term mean peak flow are required to transport bed-material sand in suspension in all regions of the multi-thread channel and that the ~2-month duration of the snowmelt flood played an important role in creating conditions necessary to maintain channel conveyance. These results indicate that detailed characterizations of channel response such as these are needed to predict how river channels will respond to changes in streamflow regime that affect annual peak flow magnitude and duration.

Movement Dynamics of Nonnative Burbot in the Upper Green River System and Implications for Management

AbstractBurbot Lota lota were illegally introduced to the Green River, Wyoming, in the mid‐1990s and pose a threat to recreational fisheries and native fish conservation. Although much is known about Burbot population dynamics, little is known about their movement patterns. Our objectives were to describe the movement dynamics of Burbot in the upper Green River system to provide information on the ecology of Burbot and insight on possible management actions. In total, 875 Burbot were tagged with PIT tags in the upper Green River and Fontenelle Reservoir; their movements were tracked from August 2016 to March 2018. Additionally, 22 Burbot were tagged with radio transmitters in Fontenelle Reservoir in November 2017, and 13 Burbot were tagged with radio transmitters in the upper Green River in November 2018. Of these fish, 11 Burbot tagged in Fontenelle Reservoir and all river‐tagged Burbot were tracked as they migrated into the Green River and associated tributaries during the spawning season. Upstream and downstream movements of Burbot tagged with PIT tags in Fontenelle Reservoir and the upper Green River peaked during December–January and were synchronized with river temperatures reaching 0°C. Of the total number of PIT‐tagged Burbot, 10–15% of those tagged in Fontenelle Reservoir were detected in the Green River during the spawning season and 15% of those tagged in the Green River were detected moving downstream toward Fontenelle Reservoir during the spawning period. Movements of radiotelemetered Burbot were synchronized with river ice‐up in mid‐December. Maximum upstream distance traveled by adfluvial Burbot was 5.8 km. Fluvial Burbot primarily migrated downstream during the spawning period, and maximum downstream distance traveled was 17.7 km. Detection data suggest that both fluvial and adfluvial Burbot occupy the same reaches during the spawning period and areas near Fontenelle Reservoir are important for spawning. Results of this study will assist with the management of Burbot in this system by shedding light on Burbot movement patterns and identifying areas of high Burbot use for targeted suppression efforts. Results also contribute to our understanding of the variability in Burbot ecology.

Factors Influencing Capture and Retention of Razorback Sucker in Light Traps

AbstractLight trap captures of larval, endangered Razorback Sucker Xyrauchen texanus are used to guide flow release timing from reservoirs and measure Razorback Sucker annual reproductive success in the Green River, Utah. However, little is known regarding efficacy of light traps to capture or retain larvae under variable and field‐relevant environmental conditions. We conducted laboratory experiments to investigate the effects of light trap set time, fish release distance from trap, light presence, turbidity, fish density, and cover on capture and retention probabilities of five early life stages of Razorback Sucker. Mean capture probability of protolarvae prior to swim bladder development (7–9 mm TL) was 0.40 (range = 0.28–0.55) over various treatments but rose to 0.76 (0.73–0.80) after swim bladder development in later protolarvae (9–10 mm TL). Mesolarvae (11–17 mm TL), the most common life stage captured in field sampling, had a similar mean capture probability (0.86; 0.82–0.90) as later protolarvae. Capture probabilities of metalarval (mean = 0.42, range = 0.21–0.63; 15–24 mm TL) and juvenile (mean = 0.24, range = 0.20–0.28; 22–37 mm TL) life stages were lower. Larvae retention probabilities were generally > 0.75 and increased to 0.97 for juveniles. Longer set times positively influenced capture probabilities, though capture probabilities were similar in 1‐, 3‐, and 5‐m release distances and relatively high (>0.75) for most the commonly sampled life stages in standard conditions. Light presence in traps greatly increased capture and retention of larvae compared with unlit traps. Our results confirm that light traps may be useful to detect first presence of Razorback Sucker larvae in Green River backwaters each spring, which triggers Flaming Gorge Reservoir releases to inundate floodplain wetlands and for annual monitoring of reproductive success. We also provide recommendations for gear set up, deployment, and techniques to increase capture and retention probabilities of Razorback Sucker larvae.

Fossil History of Curculionoidea (Coleoptera) from the Paleogene

Currently, some 564 species of Curculionoidea from nine families (Nemonychidae—4, Anthribidae—33, Ithyceridae—3, Belidae—9, Rhynchitidae—41, Attelabidae—3, Brentidae—47, Curculionidae—384, Platypodidae—2, Scolytidae—37) are known from the Paleogene. Twenty-seven species are found in the Paleocene, 442 in the Eocene and 94 in the Oligocene. The greatest diversity of Curculionoidea is described from the Eocene of Europe and North America. The richest faunas are known from Eocene localities, Florissant (177 species), Baltic amber (124 species) and Green River formation (75 species). The family Curculionidae dominates in all Paleogene localities. Weevil species associated with herbaceous vegetation are present in most localities since the middle Paleocene. A list of Curculionoidea species and their distribution by location is presented.

Population Genetics of the Wyoming Endemic Phlox pungens Dorn (Polemoniaceae)

Phlox pungens is a rare taxon restricted to cold deserts in the Wyoming Basins Ecoregion of west-central Wyoming, with occurrences in both the Wind River Basin (from which it was originally described) and the Green River Basin (populations that have been characterized as a different “morph”). The population genetics of P. pungens was investigated using microsatellite markers developed for the genus. Four microsatellite loci were genotyped from a total of 200 individuals of P. pungens from 10 sites. Ploidy levels were also assessed using flow cytometry. Most sampled populations of P. pungens were tetraploid, but 2 populations in the Green River Basin were diploid, and one high-ploidy population was discovered in the Wind River Basin. Mitotic chromosome counts were conducted for the high-ploidy site and documented the presence of 10x individuals (2n = approximately 70). Microsatellite data analysis revealed moderate genetic differentiation between populations of P. pungens, notably structured by geography with the Wind River Basin versus the Green River Basin (i.e., the 2 morphs) corresponding closely to different genetic groups. Cytotypic variation generally did not impact genetic patterns, with the exception of the high-ploidy population, which constituted a third genetic group with a high number of alleles per locus and many private alleles. The genetic differences between the 2 morphs were driven more by different allele frequencies than by fixation for different alleles at these microsatellite loci. The results of this study highlight the genetic differentiation between populations of P. pungens in the Wind River versus the Green River Basins. Moreover, P. pungens is part of a taxonomically challenging set of glandular cespitose Phlox taxa distributed in western North America, and our findings on population genetic variation in this rare taxon contribute to ongoing work on taxonomy and diversity in the Phlox study system.

New social insect nests from the Upper Jurassic Morrison Formation of Utah

This paper reports a new assemblage of social insect ichnofossils from the Brushy Basin Member of the Upper Jurassic Morrison Formation near Green River, Utah. At least seven distinct nests are visible in the locality horizon, identifiable at the outcrop scale by loci of anastomosing, and orthogonally connected hor-izontal burrows and vertical shafts. A boulder-sized block from the in situ horizon has eroded and rolled downhill, revealing the ventral aspect of the nest, showing a view of the overall nest architecture. Burrow and shaft clusters are organized into mega-galleries which have branching arms and ovate, bulbous cham-bers. The organization of distinct trace morphologies is consistent with ethological complexity of the social insects. A small sample was collected and analyzed by serial sectioning and petrographic thin sectioning to observe small-scale morphological features. Centimeter-scale analysis shows chamber, gallery, and burrow walls have complex topography. Pebble-sized, hollow, ellipsoid features are distributed throughout the up-permost facies of the nest and have undergone complete silicification of their outer surfaces. The ellipsoids share similarity with pellet structures made of mud or carton produced by modern termites. This trace fossil assemblage suggests it is possible that termites had acquired subterranean nesting behavior, and mud or carton utilization in nest construction in seasonally arid habitats by the Late Jurassic.

Controls on hydrocarbon accumulation by facies and fluid potential in large-scale lacustrine petroliferous basins in compressional settings: A case study of the Mesozoic Ordos Basin, China

Large-scale lacustrine basins in compressional settings are an important type of petroliferous basin, and the study of the characteristics of hydrocarbon accumulation in such basins is of great significance. This synthesis paper takes the Mesozoic Ordos Basin (central China) as a case study to establish lateral and vertical hydrocarbon accumulation patterns in this basin type, and highlights how facies and fluid potential control hydrocarbon accumulation in such basins. Based on systematic analyses of the Mesozoic source rocks, sedimentary facies, migration and accumulation patterns, and characteristics of the oil reservoirs, the hydrocarbon accumulation characteristics in the Mesozoic Ordos Basin are discussed. The analysis indicates that sedimentary facies controlled the characteristics and distribution of hydrocarbon source rocks and reservoirs, while diagenetic facies controlled the quality and distribution of the reservoirs. Excess pressure and fluid potential controlled hydrocarbon migration directions and paths, whereas facies and potential controlled the locations of oil accumulations and traps. It is concluded that source rocks controlled oil-bearing regions, sedimentary facies controlled oil-bearing plays, and fluid potential controlled the locations of accumulations. For shallow intervals, because fluid migration is mainly controlled by buoyancy, paleotopographic highs played an important role in controlling hydrocarbon accumulations. For deep layers (Chang 7 to Chang 10 members), since buoyancy is less than the capillary pressure, excess pressure caused by the undercompaction of mudstone and hydrocarbon generation at depth provides the driving force for lateral and vertical migration of oil, and becomes the main migration force. The reservoir accumulation characteristics differ laterally between regions of the basin; at the periphery of the basin, reservoir units are stacked in a step-wise manner, whereas at the center of the basin, multiple reservoir intervals are vertically stacked in the form of multistorey accumulations. Vertically, layers with different burial depths have different accumulation characteristics; the paleotopography controlled hydrocarbon accumulation in shallow intervals; instead excess pressure, fluid potential, and paleotopography controlled accumulation in deep intervals. This understanding could be used to inform prospecting in other large-scale lacustrine petroliferous basins in compressional settings such as the Eocene Green River Basin in the U.S.A. and the Middle Triassic Gunnedah Basin in Australia.