The Response of Fluvial Systems in the Uinta Basin, Utah to Extreme Global Warming Events During the Early Eocene Climatic Optimum

Evan Jones and Piret Plink-Björklund
Colorado School of Mines

The Wasatch and Green River Formations in the Uinta Basin contain fluvial sandstones that record terrestrial sedimentation coincident with Paleocene-Eocene Thermal Maximum (PETM) and six post-PETM hyperthermal climate change events. The Uinta Basin was one of a series of lacustrine basins isolated by Laramide uplifts in the Rocky Mountain region during the Early Eocene, and this project will better constrain the relative influence of both tectonic and climatic forcing on fluvial systems that fed sediment and water to these endorheic basins. This dataset combines quantitative petrographic analysis with carbon isotope analysis taken along measured stratigraphic sections in the southern margin of the Uinta Basin. This work shows that peak negative isotope excursions, related to pulses of greenhouse climate, correlate to regional flushing of sediment from catchment areas and progradation of fluvial systems into the lacustrine basin. This correlates to deeper channel incision, lateral and vertical amalgamation of channels, and delivery of relatively compositionally and texturally immature sediment to the basin. Understanding the compositional and textural maturity of these fluvial sandstones will provide insights into the response of chemical weathering rates, physical erosion rates, and the seasonality of sediment and water discharge to a series of global warming events. Climate change during the PETM was initiated by a release of over 2,000 gigatonnes of CO2 into the atmosphere, comparable in magnitude to that which could occur in the coming centuries from anthropogenic sources, and understanding the terrestrial response to extreme climatic forcing is important for predictive climate change modeling. Further, if terrestrial records of chemical weathering rates differ substantially from proxies developed from marine sediments, carbon-cycle dynamics during the Early Eocene Climatic Optimum must be reconsidered.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013