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Depositional Processes and Carbon Burial on a Turonian Prodelta at the Margin of the Western Interior Seaway

By
Elana L. Leithold
Elana L. Leithold
North Carolina State University, Department of Marine, Earth, and Atmospheric Sciences, Box 8208, Raleigh, North Carolina 27695
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Walter E. Dean
Walter E. Dean
U.S. Geological Survey, MS 980 Federal Center, Denver, Colorado 80225
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Published:
January 01, 1998

Abstract

Lower-middle Turonian strata of the Tropic Shale and correlative Tununk Shale Member of the Mancos Shale accumulated in muddy prodeltaic environments near the western margin of the Cretaceous Western Interior Seaway. These fine-grained rocks are well exposed in outcrops along the southern margin of the Kaiparowits Plateau and in the Henry Mountains region in southern Utah, and they have been sampled in a core drilled by the United States Geological Survey near the town of Escalante, Utah. The rocks consist of bottomset, foreset, and topset facies that accumulated at progressively increasing rates during the eastward progradation of subaqueous deltaic clinoforms. Bottomset facies accumulated in relatively distal settings where sedimentation was dominated by deposition of both terrigenous and biogenic particles from suspension. In these strata, the shapes of fecal pellets, thicknesses of event layers, and intensity of bioturbation point to relatively slow rates of sediment accumulation. Foreset and distal topset beds, in contrast, suggest more rapid sediment accumulation, primarily as the result of episodic turbidity currents and storm processes.

Within the progradational succession, upward increasing organic carbon content and hydrogen indices and decreasing values suggest that the amount of marine organic carbon buried increased over time and with proximity to the shoreline. These trends parallel evidence for both increasing rates of sediment accumulation and decreasing levels of bottom water oxygenation and are interpreted to reflect increasing preservation of labile marine carbon. Studies of the Tropic and Tununk shales suggest that along the western margin of the seaway, proximal foreset facies are major repositories of marine organic carbon.

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Contents

SEPM Concepts in Sedimentology and Paleontology

Stratigraphy and Paleoenvironments of the Cretaceous Western Interior Seaway, USA

Walter E. Dean
Walter E. Dean
U.S. Geological Survey, Denver, Colorado
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Michael A. Arthur
Michael A. Arthur
Pennsylvania State University, University Park, Pennsylvania
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SEPM Society for Sedimentary Geology
Volume
6
ISBN electronic:
9781565762299
Publication date:
January 01, 1998

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