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Paleogeography, Climate and the Carbon Cycle of the Mid-Neoproterozoic Red Pine Shale, Uinta Mountains, Northeastern Utah

Myer, Caroline A. and Carol M. Dehler
Utah State University, Logan, UT

     The Red Pine Shale, Uinta Mountain Group, northeastern Utah, is an organic-rich sedimentary succession that records information on depositional environments, paleogeography, carbon cycling, and climate of northeastern Utah during Neoproterozoic time. Data suggests deposition in a marine deltaic system open to the west and south with at least two sediment sources. The carbon-isotope record shows a fluctuating carbon cycle that may indicate changes in regional climate. Six measured sections were described for facies analysis and sampled for carbon isotope and TOC analyses, and sandstone petrography. Five facies were identified including: shale, shale-and-sandstone, sandstone, slump-fold, and concretion facies. The shale facies represents a prodelta environment, the shale-andsandstone facies represents the distal delta front, and the sandstone facies represents the delta front to delta plain. The slump-fold facies represents a proximal prodelta. The concretion facies also represents a prodelta setting and contains vase-shaped microfossils, a mid- Neoproterozoic (ca. 750 Ma) index fossil. Four measured sections in the southern range were correlated using marker beds. Using these correlations, a better understanding of facies architecture will be possible. A minimum thickness of exposed Red Pine Shale in this area is measured to 880m, and local mapping suggests a thickness of ~1200 m. C-isotope values range from -27.10 to -16.91 PDB (~20 m sample spacing) and display anomalies that have potential to be used as fingerprints for correlations, as well as for potential climate proxies. Preliminary TOC values are up to 5.91 weight percent. A higher resolution curve (~3 m sample spacing) is in progress.


AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah