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Sedimentology, Stratigraphy, and Organic Geochemistry of the Red Pine Shale, Uinta Mountains, Utah: A Prograding Deltaic System in a Mid-Neoproterozoic Interior SeawayMyer, Caroline Amelia 01 December 2008 (has links)
The Red Pine Shale (RPS; ~1120m), uppermost formation of the Neoproterozoic Uinta Mountain Group, Utah, is an organic-rich sedimentary succession that represents marine deltaic systems delivering mature sediment from the east and immature sediment from the north. Multiple data sets suggest regional climate and sea-level changes associated with changing organic carbon burial rates. Six facies identified represent wave-, tidal-, and river-influenced parts of the distal prodelta to delta front. The shale facies is interpreted as distal prodeltaic deposition in a marine environment. The concretion facies is interpreted as prodeltaic deposition to distal prodelta. The shale-sandstone facies represents suspension settling with dilute density currents in a proximal prodelta to delta front environment. The slump fold facies was deposited on the proximal prodelta or delta front. The sandstone facies represents deposition on the delta front and shows marine- and river- influences. The pebbly sandstone facies is representative of a delta front environment. C-isotope values from this shale range from -29.46 / to -16.91 / PDB and TOC from 0.04% to 5.91%. Combined H/C, TOC, and local-regional isotopic correlations suggest that these values are representative of C-isotope composition of Neoproterozoic seawater. The composite C-isotope curve for the RPS is less negative values near the base, followed by a long decline to a thick interval of homogeneous lower values. Petrographic analyses reveal immature arkosic sandstone and mature quartz arenite populations. Detrital zircon data show an Archean population from the Wyoming Craton to the north and a mixed Proterozoic/Archean population from the east-southeast. Measured sections show north to south delta progradation with a proximal source to the north and a mature sediment source to the east. The composite section shows one low-order regressive cycle and ~11 high-order cycles. There is a relationship between C-isotope values, shale geochemistry, and lithostratigraphy. Less negative C-isotope values correspond with increased kaolinite and facies indicating higher sea-level. These relationships are seen in the correlative Chuar Group, Arizona, and a similar model is suggested for their origin: humid climate, high organic carbon burial rates, and high sea-level. This paper meets the requirements to revise the RPS as a formalized unit in accordance with the Stratigraphic Code guidelines.
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Geology of the Phil Pico Mountain Quadrangle, Daggett County, Utah, and Sweetwater County, WyomingAnderson, Alvin D. 25 April 2008 (has links) (PDF)
Geologic mapping in the Phil Pico Mountain quadrangle and analysis of the Carter Oil Company Carson Peak Unit 1 well have provided additional constraints on the erosional and uplift history of this section of the north flank of the Uinta Mountains. Phil Pico Mountain is largely composed of the conglomeratic facies of the early Eocene Wasatch and middle to late Eocene Bridger Formations. These formations are separated by the Henrys Fork fault which has thrust Wasatch Formation next to Bridger Formation. The Wasatch Formation is clearly synorogenic and contains an unroofing succession from the adjacent Uinta Mountains. On Phil Pico Mountain, the Wasatch Formation contains clasts eroded sequentially from the Permian Park City Formation, Permian Pennsylvanian Weber Sandstone, Pennsylvanian Morgan Formation, and the Pennsylvanian Round Valley and Mississippian Madison Limestones. Renewed uplift in the middle and late Eocene led to the erosion of Wasatch Formation and its redeposition as Bridger Formation on the down-thrown footwall of the Henrys Fork fault. Field observations and analysis of the cuttings and lithology log from Carson Peak Unit 1 well suggest that initial uplift along the Henrys Fork Fault occurred in the late early or early middle Eocene with the most active periods of uplift in the middle and late Eocene (Figure 8, Figure 24, Appendix 1). The approximate post-Paleocene throw of the Henrys Fork fault at Phil Pico Mountain is 2070 m (6800 ft). The Carson Peak Unit 1 well also reveals that just north of the Henrys Fork fault at Phil Pico Mountain the Bridger Formation (middle to late Eocene) is 520 m (1710 ft) thick; an additional 460 m (1500 ft) of Bridger Formation lies above the well on Phil Pico Mountain. Beneath the Bridger Formation are 400 m (1180 ft) of Green River Formation (early to middle Eocene), 1520 m (5010 ft) of Wasatch Formation (early Eocene), and 850 m (2800 ft) of the Fort Union Formation (Paleocene). Stratigraphic data from three sections located east to west across the Phil Pico Mountain quadrangle show that the Protero-zoic Red Pine Shale has substantially more sandstone and less shale in the eastern section of the quadrangle. Field observations suggest that the Red Pine Shale undergoes a facies change across the quadrangle. However, due to the lack of continuous stratigraphic exposures, the cause of this change is not known.
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