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Caddisfly-dominated microbial-carbonate mounds and avian eggshell fragments are common in a nearshore, oolite facies of the Tipton Shale Member of the Eocene Green River Formation. The fossils occur in a 9 m thick carbonate sequence exposed on the south-west flank of Essex Mountain, Sweetwater County, Wyoming. The eggshell was determined to be of avian origin by examination of the radial eggshell microstructure by scanning electron microscopy and polarized light microscopy. Common allochems in the limestone include: ooids, pisoids, oncoids, ostracods, gastropods, intraclasts, caddisfly larval/pupal cases, fish bones, avian bones and avian eggshell fragments. Carbonate mineralogy varies between 95% calcite and 95%...
A new genus is described based on fossilized winged fruits from former lake deposits of Wyoming, Utah, Colorado, Oregon, and British Columbia, ranging in age from latest Paleocene to early Middle Eocene. Lagokarpos lacustris McMurran et Manchester gen. et sp. nov. fruits have an elliptical to globose seed body and a conspicuous pair of apical wings with pinnate venation. These wind�dispersed fruits are compared with and distinguished from similar extant winged fruits such as Dipterocarpus Gaertn f. (Dipterocarpaceae), Gyrocarpus Jacq. (Hernandiaceae), and Alberta E. Meyer (Rubiaceae). No modern fruit was found to exhibit the combination of characters seen in Lagokarpos, and we conclude that it represents an extinct...
Complex, caddisfly-dominated (Insecta: Trichoptera) carbonate mounds up to 9 m tall and 40 m in diameter formed in the nearshore environment of Eocene Lake Gosiute. The mounds outcrop for 70 km in reef-like geometries along the northern margin of Lake Gosiute in Wyoming. The relationships among the caddisfly larvae, the benthic microbial mat and physicochemical nearshore processes of Eocene Lake Gosiute resulted in unique external and internal carbonate mound morphology. Externally, the large carbonate mounds are formed by the lateral and vertical coalescence of several layers of smaller columns. The smaller columns are generally 1?2 m tall and are 0.5?1 m in diameter. Each layer or generation of smaller columns...
A new genus is described based on fossilized winged fruits from former lake deposits of Wyoming, Utah, Colorado, Oregon, and British Columbia, ranging in age from latest Paleocene to early Middle Eocene. Lagokarpos lacustris McMurran et Manchester gen. et sp. nov. fruits have an elliptical to globose seed body and a conspicuous pair of apical wings with pinnate venation. These wind?dispersed fruits are compared with and distinguished from similar extant winged fruits such as Dipterocarpus Gaertn f. (Dipterocarpaceae), Gyrocarpus Jacq. (Hernandiaceae), and Alberta E. Meyer (Rubiaceae). No modern fruit was found to exhibit the combination of characters seen in Lagokarpos, and we conclude that it represents an extinct...
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Carbon isotopic compositions of saturated hydrocarbon, aromatic hydrocarbon, NSO (resin), and asphaltene fractions of vein-forming gilsonites (Cowboy, Bonanza, Independence, Wagonhound and Harrison veins) in the NE Uinta Basin, Utah, are all similar and isotopically resemble Mahogany Zone shale extracts of the Green River Formation (δ 13C −29 to −31%). Individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the Eocene Uinta/Greater Green River paleolake system. Carbon isotopic compositions of C28 and C29 steranes (δ 13C = −25 to −32%), pristance and phytane (−33 to —34%) and perhydroβ-carotene (carotane) (δ 13C = −33.2%) suggest that...
This study is the first to employ spectral analysis to examine meter-scale sedimentary cyclicity in the Wilkins Peak Member of the lower Eocene Green River Formation of Wyoming. Generally regarded as the classic example for orbital forcing of lacustrine sediments at eccentricity and precession time scales, this long-standing interpretation was recently contested, with a much shorter duration (≤ 10 ky) inferred for the dominant cyclicity. Earlier work lacked adequate age control or spectral analysis or both. Our analysis is based upon an evaluation in the frequency domain of oil-yield values from four boreholes, accuracy estimation for suggested orbital interpretations, and comparison to independent geochronology....
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Sandstone bodies in the Sunnyside Delta Interval of the Eocene Green River Formation, Uinta Basin, previously considered as point bars formed in meandering rivers and other types of fluvial bars, are herein interpreted as delta mouth-bar deposits. The sandstone bodies have been examined in a 2300 m long cliff section along the Argyle and Nine Mile Canyons at the southern margin of the Uinta lake basin. The sandstone bodies occur in three stratigraphic intervals, separated by lacustrine mudstone and limestone. Together these stratigraphic intervals form a regressive-transgressive sequence. Individual sandstone bodies are texturally sharp-based towards mudstone substratum. In proximal parts, the mouth-bar deposits...
An extinct genus of the Polemoniaceae is described from one complete fossil plant preserved in shale of the Eocene Green River Formation, Utah. Combined vegetative and reproductive characters including the taproot, basal and cauline pinnatifid leaves, primary peduncular leaves, secondary peduncular bracts, pedicel bracts, fruits in groups of three, and persistent calyx, support placement of this plant close to the extant genus Gilia. Gilisenium hueberi gen. et sp. nov. represents a rare record of an herbaceous plant, and the oldest megafossil for the family Polemoniaceae. Published in Review of Palaeobotany and Palynology, volume 104, issue 1, on pages 39 - 49, in 1998.
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Two members of the Green River Formation in the Washakie Basin have been analysed by organic geochemical and organic petrographic techniques and the results placed in a sequence stratigraphic framework. One of these members, the Laney Shale, was deposited in a hydrologically closed, alkaline lake under an arid climate and was characterized by high concentrations of alginite-rich organic matter whereas the other, the Luman Tongue, was deposited in a hydrologically open, freshwater lake under a humid climate and consisted of organic-poor profundal lake mudstones and coaly lake margin sediments. Potential source rocks in both lake types have the potential for generating high-wax oil at high subsurface temperatures...
Results of extraction experiments performed on immature Green River Formation source rock samples from the Black Shale Facies (Uinta Basin, Utah) demonstrate the potential of extracting high molecular weight hydrocarbons (HMWHC) with sequential dichloromethane:methanol/soxhlet and p-xylene/sonication techniques. The first soxhlet extraction step with DCM:MeOH removes lower molecular weight alkanes from the source rock while the HMWHC remain in the rock residue. Sonication of the rock residue with p-xylene recovers these HMWHC, showing distinct hydrocarbon distributions and preferences in high temperature gas chromatograms. Extracts obtained by using p-xylene/soxhlet with original source rocks and sequential soxhlet...
The sedimentary record of Lake Gosiute, a lake that existed in southwestern Wyoming during the Eocene, contains evidence for lake level fluctuations thought to be caused by the earth's precession cycle. However, it is not clear how the effects of these orbital variations were transferred through the climate system and into the sedimentary record. We carry out a series of experiments using a general circulation model (GCM), a lake energy balance model and a lake water balance model to better understand the processes by which these orbital variations could have altered lake evaporation, on-lake precipitation and runoff from the lake's catchment. GCM simulations indicate significant differences in surface incident...
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Numerous 40Ar/39Ar experiments on sanidine and biotite from 22 ash beds and 3 volcaniclastic sand beds from the Greater Green River, Piceance Creek, and Uinta Basins of Wyoming, Colorado, and Utah constrain ~8 m.y. of the Eocene Epoch. Multiple analyses were conducted per sample using laser fusion and incremental heating techniques to differentiate inheritance, 40Ar loss, and 39Ar recoil. When considered in conjunction with existing radioisotopic ages and lithostratigraphy, biostratigraphy, and magnetostratigraphy, these new age determinations facilitate temporal correlation of linked Eocene lake basins in the Laramide Rocky Mountain region at a significantly increased level of precision. To compare our results...
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The deposits of Eocene Lake Gosiute that constitute the Green River Formation of Wyoming contain numerous tuff beds that represent isochronous, correlatable stratigraphic markers. Tuff beds selected for 40Ar/39Ar analysis occur within laminated mudstone, are matrix supported, and lack evidence of reworking. These tuffs contain 2%?15% euhedral phenocrysts of quartz, plagioclase, sanidine, biotite, and minor amphibole, pyroxene, and zircon, encased in a matrix of altered glassy ash. Air abrasion and handpicking under refractive- index oils were required to obtain clean, unaltered phenocrysts of sanidine. 40Ar/39Ar age determinations from single-crystal and <1 mg multigrain aliquots of sanidine and biotite allowed...
We reevaluate the Eocene geomagnetic polarity time scale on the basis of single-crystal 40Ar/39Ar ages for air-fall tuffs from the Wilkins Peak Member of the Green River Formation of Wyoming. Tuff 6 is dated as 49.1 � 0.2 Ma, and tuff 3 is dated as 50.4 � 0.3 Ma (maximum estimate). When combined with published magnetostratigraphic constraints, these age determinations suggest that the currently accepted age of chron C22r is 1.5?2.5 m.y. too old, which supports a significantly longer duration for the early Eocene, for the early Eocene climatic optimum, and the Wasatchian North American Land Mammal Age. Published in Geology, volume 32, issue 2, on pages 137 - 137, in 2004.
Bedded trona (Na2CO=-NaHCO=.214,0) in the lacustrine Green River Formation of Eocene age in the Green River Basin, southwest Wyomin~ constitutes the largest known resource of natural sodium carbonate in the world, in this study, 116 gigatons (Gt) of trona ore are estimated to be present in 22 beds, ranging from 1.2 to 11 meters (m) in thickness. Of this total, 69 Gt of trona ore are estimated to be in beds containing less than 2 percent halite and 47 Gt in beds containing 2 or more percent halite. These 22 beds underlie areas of about 130 to more than 2,000 km: at depths ranging from about 200 m to more than 900 m below the surface. The total resource of trona ore in the basin for which drilling Information is available...
A newly recovered twig with attached leaves and flowers from the Eocene Green River Formation of Utah provides the basis for recognizing a new, extinct genus of Salicaceae sensu lato (s.l.). Pseudosalix handleyi gen. et sp. nov. has alternate lanceolate leaves with pinnate, semicraspedodromous venation and a serrate margin with glandular teeth. The inflorescence is terminal on the twig and is unisexual, composed of flowers organized in a paniculoid cyme, with lateral paraclades of pedicellate flowers. The attached pistillate flowers have four prominent sepals that are valvate in bud, spreading but basally fused at anthesis; the single pistil of each flower is ovoid with three or four longitudinal sutures, indicating...
A case study of Munsell color measurements from the Eocene Colton and Green River Formations in central Utah shows how easily stereoscopic triaxial scatterplots can display the limited overlap of colors within lacustrine and alluvial facies. Grays, drabbish yellow-greens, greens, and 10 YRs are associated with lacustrine limestones and other known lacustrine facies, whereas other yellow-reds and reds are predominantly associated with terrestrial deposits, including fluvial sandstones. Lake beds in Colton Formation show a greater variety of color than those in the Green River Formation, both in terms of a greater range of hues and more extreme lightness and darknesses, apparently reflecting the fact that the Green...


    map background search result map search result map Carbon isotopic composition of individual biomarkers in gilsonites (Utah) Recognition and significance of sharp-based mouth-bar deposits in the Eocene Green River Formation, Uinta Basin, Utah Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A. Synoptic reconstruction of a major ancient lake system: Eocene Green River Formation, western United States Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute 40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming Recognition and significance of sharp-based mouth-bar deposits in the Eocene Green River Formation, Uinta Basin, Utah Carbon isotopic composition of individual biomarkers in gilsonites (Utah) Palaeoenvironments associated with caddisfly-dominated microbial-carbonate mounds from the Tipton Shale Member of the Green River Formation: Eocene Lake Gosiute Organic geochemistry of freshwater and alkaline lacustrine sediments in the Green River Formation of the Washakie Basin, Wyoming, U.S.A. 40Ar/39Ar geochronology of the Eocene Green River Formation, Wyoming Synoptic reconstruction of a major ancient lake system: Eocene Green River Formation, western United States