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Full-Text Articles in Physical Sciences and Mathematics
Geologic Mapping Of The Vernal Nw Quadrangle, Uintah County, Ut, And Stratigraphic Relationships Of The Duchesne River Formation And Bishop Conglomerate, Casey Andrew Webb
Geologic Mapping Of The Vernal Nw Quadrangle, Uintah County, Ut, And Stratigraphic Relationships Of The Duchesne River Formation And Bishop Conglomerate, Casey Andrew Webb
Theses and Dissertations
Detailed mapping (1:24,000), measured sections, and clast counts in conglomerates of the Duchesne River Formation and Bishop Conglomerate in the Vernal NW quadrangle in northeastern Utah reveal the middle Cenozoic stratigraphic geometry, the uplift and unroofing history of the eastern Uinta Mountains, and give evidence for the pulsed termination of Laramide uplift. The Unita Mountains are an EW-trending reverse fault bounded and basement-cored, Laramide uplift. The oldest unit of the Duchesne River Formation, the Eocene Brennan Basin Member, contains 80-90% Paleozoic clasts and <20% Precambrian clasts. Proximal to the Uinta uplift the conglomerates of this member are dominated by Paleozoic Madison Limestone clasts (70-90% of all clasts). Farther out into the basin, Paleozoic clasts still dominate in Brennan Basin Member conglomerates, but chert clasts are more abundant (up to 43%) showing the efficiency of erosion of the carbonate clasts over a short distance (~5 km). Conglomerates in the progressively younger Dry Gulch Creek, Lapoint, and Starr Flat members show a significant upward increase in Precambrian clasts with 34-73% Uinta Mountain Group and 8-63% Madison Limestone. Duchesne River Formation has a significant increase in coarse-grained deposits from the southern parts of the quadrangle (20-50% coarse) to the northern parts (75% coarse) nearer the Uinta uplift. The lower part of the Duchesne River Formation exhibits a fining upward sequence representing a tectonic lull. Clast count patterns show that pebbly channel deposits in the south maintain similar compositions to their alluvial fan counterparts. To the north, the fine-grained Lapoint and Dry Gulch Creek members of the Duchesne River Formation appear to pinch out completely. This can be explained by erosion of these fine-grained deposits or by lateral facies shifts before deposition of the next unit. Starr Flat Member conglomerates were deposited above Lapoint Member siltstones and represent southward progradation of alluvial fans away from the uplifting mountain front. Similarities in composition and sedimentary structures have caused confusion surrounding the contact between the Starr Flat Member and the overlying Bishop Conglomerate. Within the Vernal NW quadrangle, we interpret this contact as an angular unconformity (the Gilbert Peak Erosion Surface) developed on the uppermost tilted red siltstone of the Starr Flat Member sometime after 37.9 Ma. Stratigraphic and structural relationships reveal important details about the development of a Laramide mountain range: 1) sequential unroofing sequences in the Duchesne River Formation, 2) progradation of alluvial fans to form the Starr Flat Member, 3) and the unconformable nature of the Gilbert Peak Erosion Surface lead to the conclusion that there were at least 3 distinct episodes of uplift during the deposition of these formations. The last uplift episode upwarped the Starr Flat Member constraining the termination of Laramide uplift in the Uinta Mountains to be after deposition of the Starr Flat Member and prior to deposition of the horizontal Bishop Conglomerate starting at about 34 Ma. This, combined with 40Ar/39Ar ages of 39.4 Ma from the Dry Gulch Creek and Lapoint member, show …
Variable Uplift From Quaternary Folding Along The Northern Coast Of East Timor, Based On U-Series Age Determinations Of Coral Terraces, Nicole L. Cox
Variable Uplift From Quaternary Folding Along The Northern Coast Of East Timor, Based On U-Series Age Determinations Of Coral Terraces, Nicole L. Cox
Theses and Dissertations
Surveys of emergent terraces and U-series ages for ten sites along the coast of East Timor provide estimates of late Quaternary differential vertical strain in the most mature region of the Banda Arc-continent collision complex. Over a distance of ~180 km vertical displacement rates vary between 0.0 and 1.6 meters per 1000 years for the last 150,000 years. Two models of terrace formation (constructional and erosional) are applied to interpret terrace ages from coral ages and to estimate uplift rates. The highest uplift rates are from three sites over a distance of 15 km along the coast. Uplift rates were …
Geology Of The Phil Pico Mountain Quadrangle, Daggett County, Utah, And Sweetwater County, Wyoming, Alvin D. Anderson
Geology Of The Phil Pico Mountain Quadrangle, Daggett County, Utah, And Sweetwater County, Wyoming, Alvin D. Anderson
Theses and Dissertations
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 …
Long-Term Surface Uplift History Of The Active Banda Arc-Continent Collision: Depth And Age Analysis Of Foraminifera From Rote And Savu Islands, Indonesia, Nova Roosmawati
Theses and Dissertations
Analysis of foraminifera for synorogenic pelagic units of Rote and Savu Islands, Indonesia, reveals high rates of surface uplift in the past 1.5 Ma of the incipient Banda arc-continent collision. Paleodepth estimates are derived from benthonic forams and ages from planktonic forams. But estimates are complicated, however, by abundant reworking; yet several distinctive species have been found. Synorogenic deposits in western Rote yield forams of biozone Neogene (N) 18 and depths from 5000-5700 meters at the base of the section, and 3600 meters at the top of the section. Eastern Rote yields forams of N 19/20 - N 22 and …