The Quaternary Stratigraphy of the Henrys Fork and Western Browns Park, Northeastern Uinta Mountains, Utah and Wyoming (original) (raw)
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THE LACUSTRINE GREEN RIVER FORMATION: HYDROCARBON POTENTIAL AND EOCENE CLIMATE RECORD, 2022
The 15-to 65-m-thick informal Uteland Butte member of the Eocene Green River Formation represents the first widespread transgression of Lake Uinta in the Uinta Basin, Utah. This study assesses the spatial and temporal variation of Uteland Butte member deposits along a 40-km transect in the southwestern margin of the Uinta Basin using detailed measured sections, organic and inorganic geochemical data, and outcrop gamma ray logs. Fourteen lithofacies are identified, which comprise seven facies associations linked to with lacustrine, palustrine, and deltaic depositional settings. Facies associations are traceable laterally across the study area, where five 4-to 12-m-thick depositional cycles are identified. Each shallowing upwards cycle is defined by a >1.5-m-thick basal package of organic-rich, argillaceous laminated mudstone, and is capped by thick packages of bedded carbonate. In the far western study area (Kyune Creek Canyon), thick deposits of organic-rich mudstone are present and represent the most distal outcrop section; time-equivalent strata in the eastern study area (Minnie Maud Creek Canyon) are relatively organic lean with higher silt and clay content, interpreted to represent proximal lake margin deposits influenced by a nearby delta. The outcrop belt is correlated to more distal cores and well logs across the western Uinta Basin. Similar lithological and petrophysical patterns across the western Uinta Basin are used to subdivide stratigraphy into nine laterally contiguous sub-units based on nomenclature from the oil-producing area of the central basin (from base to top: lower Uteland Butte, D Bench, D Shale, C Bench, C Shale, B Bench, B Shale, A Bench, and A Shale). Siliciclastic clay-rich and carbonaterich intervals are correlated across the region and indicate distinct siliciclastic-and carbonate-dominated lake phases during Uteland Butte member deposition. Climate is interpreted to be the dominant driver of these claycarbonate cycles, in which relatively humid periods resulted in increased fluvially derived siliciclastic sediment into the basin (clay-rich periods), and arid periods resulted in evaporative conditions with decreased fluvial sediment input that favor carbonate accumulation. Climatically driven depositional cycles within the Uteland Butte member reflect, to a smaller degree, the larger scale climatically driven depositional cycles observed at the member-and formation levels of Paleocene and Eocene Uinta Basin stratigraphy. Importantly, the Uteland Butte member clay-carbonate cycles showcase how relatively small-scale climate shifts can impact basin-scale lacustrine deposition.
Latest Quaternary glacial and periglacial stratigraphy, Wind River Range, Wyoming
We use relative dating criteria to document post-depositional alteration of till and periglacial deposits, and to map these deposits as facies of four allostratigraphic units (alloformations) in the Wind River Range. The alloformations are composed of till as well as rock-glacier, protalus-rampart, and rock fall deposits of latest Pleistocene and Holocene age. These deposits record paleoclimatic events over the past ca. 12.8 ka that infl uenced geomorphic processes in and near cirques and heads of glacial valleys of the Wind River Range. All of the type areas are on till. The oldest alloformation is the Temple Lake. Progressively younger units are the Alice Lake and Black Joe. The youngest unit is the Gannett Peak. Radiocarbon and cosmogenic radionuclide analyses provide numeric age control for these deposits. Combined numeric and relative age-data suggest the following broad age estimates for these alloformations: the Temple Lake is coeval with the Younger Dryas climate event (ca. 12,800-11,500 yr B.P.); Alice Lake is >4500 years old (ca. 6000 yr B.P.); Black Joe is ca. 1900 yr B.P. (minimum); and Gannett Peak is ca. 750-150 years old.
Sedimentary Geology, 2001
The Neoproterozoic Uinta Mountain Group was deposited in an east-trending intracratonic rift bounded on the north by an active fault system and opening into a shallow sea on the west where the Big Cottonwood Group was deposited in an estuary. Although this rift may have been associated with the early stages in the breakup of Rodinia, it was not an aulacogen. Geochemical, Nd isotope, and detrital mode studies indicate that Uinta Mountain Group sediments were derived from mixed Archean and Paleoproterozoic sources with the former dominating. Big Cottonwood Group sediments appear to have been derived predominantly from Paleoproterozoic sources. The Archean sediment source is the Wyoming craton, and source rocks comprised dominantly granites enriched in Th, U, Y, Zr, Hf, and REE. The relative abundance of enriched granite implied by sedimentary rocks of the Uinta Mountain Group indicates that the Wyoming craton is anomalous compared to other Archean cratons. CIA values and A±CN±K relationships in shales of the Uinta Mountain and Big Cottonwood groups indicate high degrees of weathering of sources, probably in subtropical to tropical climates supporting a near-equatorial location for southwestern Laurentia at about 800 Ma. Differences in the Nd isotopic composition between the Big Cottonwood Group and Neoproterozoic sedimentary rocks in western Utah and northeast Nevada suggest a northwest-striking uplift in northwest Utah, possibly ancestral to the Paleozoic Toole±Uinta arch.
Glacial stratigraphy of Stough Creek Basin, Wind River Range, Wyoming
Geomorphology, 2002
Multiparameter relative-age (RA) techniques identify four post-Pinedale morphostratigraphic units in each of three cirque valleys tributary to Stough Creek Basin, Wind River Range, WY. Soil development, lichenometry, boulder weathering characteristics, and the geomorphic relations among morphostratigraphic units indicate glacial deposits here correspond to the sequence previously described in the Temple Lake valley [Arct. Alp. Res. 6 (1974) 301]. Cirque deposits in Stough Creek Basin correspond to the Temple Lake, Alice Lake, Black Joe, and Gannett Peak alloformations [GSA Abs. Prog. 32 (2000) A-16]. 10Be ages from moraine boulders and polished-striated bedrock [Assoc. Am. Geogr. Annu. Mtg. Abs. (2000) 155] support recent numeric age estimates from Temple Lake and Titcomb Basin that indicate the Temple Lake Alloformation corresponds to the Younger Dryas climate episode [Geogr. Phys. Quat. 41 (1987) 397; Geology 23 (1995) 877; Science 268 (1995) 1329; GSA Abs. Prog. 31 (1999) A-56]. Soils described from Pinedale recessional deposits here represent the first systematic description of Pinedale alpine deposits in the WRR.
Geology of the Intermountain West, 2022
The Uinta Mountains are an east-west-trending, reverse fault-bounded, basement-cored Laramide uplift. The Eocene Duchesne River Formation and Oligocene Bishop Conglomerate represent late stage, intermontane basin fill of the Uinta Basin in northeastern Utah. Detailed mapping (1:24,000 scale), clast counts in conglomerate beds, description of lithology and stratigraphic contacts, and radiometric dating of pyroclastic fall beds of the Duchesne River Formation and Bishop Conglomerate in the Vernal NW quadrangle in northeastern Utah reveal stratal geometries of middle Cenozoic depositional units, the uplift and unroofing history of the eastern Uinta Mountains, and give evidence for the pulsed termination of Laramide uplift related to rollback of the Farallon slab and lithospheric delamination. These relationships show the continuation of Laramide uplift in this region until after 37.9 Ma and before 34 Ma, an age younger than the previously reported 45 to 40 Ma. The Duchesne River Formation consists of four members: the Brennan Basin, Dry Gulch Creek, Lapoint, and the Starr Flat. A normal unroofing signal is found within the formation with a downward increase in Paleozoic clasts and an upward increase in Proterozoic clasts. The oldest member, the Brennan Basin Member contains 80% to 90% Paleozoic clasts and less than 20% Proterozoic clasts. Conglomerate beds in the progressively younger Dry Gulch Creek, Lapoint, and Starr Flat Members of the Duchesne River Formation show significant increases in Proterozoic clasts (34% to 73%) and a decrease in Paleozoic clasts (27% to 66%). The Bishop Conglomerate overlies the Duchesne River Formation, but shows no clear change in clast composition. In the Duchesne River Formation, the proportion of beds containing fine gravel to boulder-sized clasts decreases significantly with distance from the Uinta uplift, from almost 100% near the source (<0.5 km) to 50% to 20% 10 km to the south. The lower part of the Duchesne River Formation exhibits a fining upward sequence that may represent a lull in tectonic uplift. The fine-grained lithofacies of the Dry Gulch Creek and Lapoint Members of the Duchesne River Formation pinch out within about 1 to 2 km from the Uinta uplift. In this proximal region conglomerates equivalent in age to the Lapoint Member cannot be separated from the younger conglomerates of the Starr Flat Member and are mapped together as one unit. Where the fine-grained lithologies appear farther from the uplift, the Starr Flat Member conglomerates deposited above Lapoint Member siltstones represent a southward progradation of alluvial fans away from the uplifting mountain front. The Starr Flat Member is overlain by the Bishop Conglomerate. These units are similar in sedimentary structure and clast composition and are distinguished by an angular unconformity that developed after 37.9 Ma. Stratigraphic and structural relationships between the Duchesne River Formation and Bishop Conglomerate reveal evidence of at least three episodes of Laramide-age uplift of the Uinta Mountains during the deposition of these formations: (1) deposition of fining upward sequences beginning with a basal coarse-grained unit within the Brennan Basin Member, Dry Gulch Creek Member, and Lapoint Member; (2) progradation of alluvial fans to the south form the younger Starr Flat Member resulted from an increase in sediment supply likely associated with renewed uplift; and (3) tilting and truncation of Duchesne River Formation to form the Gilbert Peak erosional surface, and prograding alluvial fans of the Bishop Conglomerate. These episodes of pulsed uplift are possibly the result of dripping lithosphere that occurred during Farallon slab rollback. New 40Ar/39Ar ages of 39.4 Ma from ash beds in the Dry Gulch Creek and Lapoint Members emplaced from Farallon rollback volcanism help to constrain the timing of deposition and uplift. These new ages and other existing radiometric and faunal ages suggest a significant unconformity of as much as 4 m.y. between the Duchesne River Formation and the overlying Bishop Conglomerate, which ranges from 34 to 30 Ma in age and show that Laramide uplift continued after 40 Ma in this region.
Age determinations of non-marine sandstones and conglomerates generally rely on fossils and/or direct dating of volcanic ash. However, in fluvial deposits where air-fall tuff comprises a significant proportion of the sediment, U-Pb dating of detrital zircons can provide ages accurate to within 1 to 2 million years of depositional ages. This suggestion stems from several new U-Pb ages of detrital zircons acquired from a suite of conglomerate and sandstone samples from the Oligocene Bishop Conglomerate and Miocene Browns Park Formation in southwestern Wyoming and northwestern Colorado. The oldest maximum depositional U-Pb ages (MDA) for these samples are from Bishop Conglomerate outcrops in the southern Green River Basin (ca. 35-34 Ma). The Bishop is overlain by tuffaceous sandstone and siltstone that produced an MDA of ca. 33-31 Ma. In northwestern Colorado, Bishop Conglomerate is overlain by tuffaceous sandstone and siltstone of the Browns Park Formation with MDAs ranging from ~24-8 Ma. Collectively, the samples show consistently younger MDAs upsection. Tuffaceous components of Bishop Conglomerate and Browns Park deposits are air-fall ash derived from Basin and Range caldera complexes in southern Utah and Nevada. Radiometric ages of Basin and Range tuff units help constrain interpretations of Bishop and Browns Park MDAs. For example, the ca. 35-34 Ma MDA of the Bishop Conglomerate in Wyoming is consistent with the ~35.8 Ma tuff of the Stone Cabin Formation in the Basin and Range. However, zircon grains from the younger 31.7 Ma tuff of the Windows Butte Formation are absent from the 35-34 Ma Bishop Conglomerate sample, but are abundant in the overlying 33-31 Ma Bishop tuffaceous sandstone. In summary, we suggest that the MDAs from these deposits generally closely represent their depositional age. The quasi-continuous nature of Oligocene through Miocene caldera eruptions in the Basin and Range Province provided a continuous supply of air-fall ash that drifted across Utah, southern Wyoming and northern Colorado. Subsequent reworking of volcanic ash by rivers produced tuffaceous sandstones and conglomerates. These results suggest that other geologic periods characterized by quasi-continuous volcanic input, such as the Late Cretaceous of the western U.S., may permit similar dating of siliciclastic rocks.
Late Cretaceous to Early Tertiary tectonostratigraphy of southwestern Utah
Museum of Northern Arizona Bulletin, v. 59, p. 181-188, 1993
The Upper Cretaceous to Paleogene sedimentary rocks of southwestern Utah record three temporally overlapping tectonic phases: 1) active Sevier-style thrust activity and foreland sedimentation; 2) cessation of thrust activity; and 3) active Laramide-style folding and intermontane sedimentation. The formations recording this tectonic evolution are, from oldest to youngest: the Iron Springs (and eastern equivalents), Kaiparowits, Canaan Peak, Grand Castle (new informal name), Pine Hollow, and Claron formations. Tbe Santonian to lower Campanian(?) upper part of the Iron Springs and mid-to-upper Campanian Kaiparowits formations represent synorogenic, fluvial sedimentation derived from the Sevier fold and thrust belt. The Iron Springs Formation received sediment from Precambrian to Upper Paleozoic strata exposed in the Wah Wah and Blue Mountain thrust sheets of southwestern Utah. The upper Campanian(?) to lower Paleocene Canaan Peak Formation was deposited in an east-to-northeast-directed, braided fluvial system. Petrographic and geochemical analysis of volcanic and siliceous clasts indicate that the Canaan Peak and Kaiparowits formations were derived from the Jurassic Deifonte Volcanics of southeastern California and the Mississippian Eleana Formation of southern Nevada. The early Paleocene Grand Castle formation represents an east- to southeast-flowing braided river system. Clast and sandstone lithologies indicate that the Grand Castle formation had the same provenance as the Iron Springs Formation. Conglomerate of the Grand Castle formation overlaps the easternmost Sevier thrust faults, suggesting a post-Sevier origin. The lower Pine Hollow Formation records active Laramide partition of the foreland basin associated with the development of the Johns Valley anticline and possibly the Circle Cliffs uplift. Fluvial, deltaic, and lacustrine deposits of the Claron Formation overlap paleotopographic highs of the Pine Hollow basin and indicate cessation of Laramide deformation by the middle Eocene.
Evidence for Quaternary tectonism in the northern Bighorn Basin, Wyoming and Montana
Geology, 1985
Irregularities in the reconstructed gradients of latest Pliocene and Quaternary terraces in the northern Bighorn Basin, northwest Wyoming and south-central Montana, suggest that Quaternary movements have occurred on the Frannie anticline, the Nye-Bowler-Sage Creek fault zone, and the North Pryor fault. This area has been considered tectonically inactive. The timing of the interpreted movements iis derived from age estimates of fluvial deposits determined from numerical ages and altitudes of associated deposits of volcanic ash. South of the Pryor Mountains, the 1.4 Ma Polecat Bench terrace of the Shoshone River rises 6-7 m over the axis of the Frannie anticline; this displacement may be related to folding or faulting since 1.4 Ma. Near the Nye-Bowler-Sage Creek and North Pryor faults in the Pryor Mountains, bedrock is 25 and 55 m shallower than depths predicted from the projected 1.4 Ma gradient of the Shoshone River through Pryor Gap. The 2.0 Ma terrace of Rock Creek may have been offset up to 7 m by a splay of the Nye-Bowler fault zone between 2.0 and 0.6 Ma. The downstream divergence of terraces along Rock Creek suggests ongoing uplift of the northern Bighorn Basin, perhaps caused by crustal rebound due to post-Oligocene erosion. 109° 108° Figure 1. Sketch map showing selected geomorphic and structural features in northern Bighorn Basin. Numbers 1-4 indicate areas discussed in text. YNP = Yellowstone National Park. Arrows mark reference elevations (m) used to calculate incision rates and also mark Lava Creek (LC) and Huckleberry Ridge (HR) ash sites. Query (?) indicates uncertain correlation of terraces or fault zones. Map modified from Reheis (1984). "<25? EXPLANATION 2-Ma terrace and drainage system Polecat Bench terrace and profile line of Fig. 2 0.6-Ma terrace major faults, bar and ball on downthrown side