6 A Matter of Time II: Using High-Resolution Stratigraphic and Sedimentologic Techniques to Investigate the Mid-Continent Geologic Record

Monday, 19 April 2021
8:00 AM - 12:00 PM
UALR Earth Science Room

CARBONATE CARBON ISOTOPE CHEMOSTRATIGRAPHY FROM THE RUBY RANCH MEMBER OF THE CEDAR MOUNTAIN FORMATION IN THE WESTERN SAN RAFAEL SWELL

Paper number: 6-8
Program: Theme Sessions
Time: 9:45 AM – 9:55 AM

Authors

Abstract

The Ruby Ranch Member of the Cedar Mountain Formation in East-Central Utah represents terrestrial deposits in the early Cretaceous Period. This member has been studied at multiple field locations and has been determined to span the Aptian-Albian Boundary based on chemostratigraphic and detrital zircon studies. The study location presented here, Moore Cutoff Road, is further west than previous studies, and thought to be a more expanded section that may contribute more detail to the chemostratigraphic and paleoclimatic record. The Ruby Ranch Member in this area consists mainly of reddish grey and greenish gray silty-sandy mudstones with abundant carbonate nodules suggestive of paleosol development. For this study samples were collected approximately every 25 cm and were used to construct a C-isotope curve using carbonate carbon. These were used to compare to existing bulk sedimentary organic carbon isotope curves. A total of 48 samples were analyzed and values from -7.45 ‰ vs. VPDB to -3.52 ‰ vs. VPDB were observed. The C-isotope data follows the trend of existing organic carbon isotope curves which exhibits the C10 positive isotope excursion near the Aptian-Albian boundary. A subset of samples will be analyzed for clumped isotope paleothermometry to test a hypothesis that this positive isotope excursion corresponds with a late Aptian “cold snap” in an otherwise greenhouse climate.

Geological Society of America Abstracts with Programs. Vol. 53, No. 3

doi: 10.1130/abs/2021NC-362752

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