Date of Award:

12-2008

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Carol M. Dehler

Committee

Carol M. Dehler

Committee

W. David Liddell

Committee

Peter T. Kolesar

Abstract

The Red Pine Shale (RPS; ~1120m thick), uppermost formation of the Neoproterozoic Uinta Mountain Group, Utah, is an organic-rich sedimentary succession interpreted as a marine deltaic system that delivered immature sediment from the north that mixed with mature sediment from the east. Multiple data sets suggest regional climate and sea-level changes associated with changing organic-carbon burial rates.

Six facies were identified and represent wave-, tidal-, and river-influenced parts of the distal prodelta to delta front in a marine system. These include the shale facies and associated concretion facies (distal prodelta), the shale-sandstone facies (proximal prodelta to delta front), the slump fold facies (proximal prodelta to delta front), and the sandstone facies and associated pebbly sandstone facies (delta front).

C-isotope values from organic-rich shale range from -29.46‰ to -16.91‰ PDB and TOC values range from 0.04% to 5.91%. The composite C-isotope curve for the RPS shows less negative values near the base, followed by a long decline to a thick interval of lower values. Combined H/C, TOC, and local-regional isotopic correlations suggest that these values represent C-isotope composition of Neoproterozoic seawater.

Provenance data sets show two distinct detrital zircon signatures. An arkosic sample shows an Archean population, most likely from the Wyoming Craton to the north. Data from two quartz arenite samples show a mixed Proterozoic/Archean population from the east-southeast. Correlation of measured sections show north to south delta progradation with a proximal source to the north and a mature source to the east. The composite section comprises one low-order regressive cycle and ~11 high-order cycles.

There is a relationship between C-isotope values, shale geochemistry, and lithostratigraphy. Relatively positive C-isotope values correspond with increased kaolinite abundance and more distal depofacies indicating an increase in organic-carbon burial and chemical weathering rates, and a rise in sea level. Relatively negative C-isotope values correspond with lower kaolinite abundances and more proximal depofacies indicating a decrease in organic-carbon burial and chemical weathering rates, and sea-level fall. Similar relationships are seen in the correlative Chuar Group, Arizona, suggesting a regional or possibly global control on these related processes.

This paper meets the requirements to revise the RPS as a formalized unit in accordance with the Stratigraphic Code guidelines.

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Comments

This work was revised and made publicly available electronically on July 26, 2011

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