Geological Society of America

T151 Modern and Ancient Continental Depositional Environments: Linking Landscape Evolution with Fluvial Systems and Lacustrine Basins through the Cenozoic

Monday, 20 October 2014
1:00 PM - 5:00 PM
211

HIGH RESOLUTION CORRELATION OF EOCENE LAKE DEPOSITS (GREEN RIVER FORMATION, WYOMING) USING SR –ISOTOPE CHEMOSTRATIGRAPHY

Paper number: T151-11
Program: Technical Sessions
Time: 3:30 PM – 3:45 PM

Authors

M'bark Baddouh Presenting Author
George Mason University, Farifax, VA
Alan Carroll
Univ Wisconsin - MadisonDepartment of Geoscience, Madison, AZ
Stephen R. Meyers
University of Wisconsin-Madison, Madison, WI
Brian Beard
University of Wisconsin-Madison, NASA Astrobiology Institute, Madison, WI
Clark Johnson
University of Wisconsin-Madison, NASA Astrobiology Institute, Madison, WI

Abstract

Lacustrine deposits are often difficult to accurately correlate, due to their intrinsically high spatial and temporal variability. In this study we investigate the use of Sr-isotope chemostratigraphy to develop a high-resolution correlation between two rock cores of the Eocene Green River Formation (Black Fork core #1 and White Mountain core #1). In the Black Forks core # 1, ⁸⁷Sr/⁸⁶Sr ratios range from 0.71156 to 0.71482, with an average of 0.71252. In the White Mountain core #1, ⁸⁷Sr/⁸⁶Sr ratios range from 0.71154 to 0.71504, with an average of 0.71268. Lower ratios consistently correspond to deeper (profundal) lacustrine facies, and higher ratios correspond to shallower (littoral and lake plain) facies. ⁸⁷Sr/⁸⁶Sr ratios do not correlate to sample mineralogy. We therefore conclude that they record changing provenance of Eocene Lake Gosiute waters during lake level fluctuations, rather than fractionation during carbonate precipitation.

We infer from these results that Sr was well mixed in the central part of Eocene Lake Gosiute, across spatial scales of at least tens of km. ⁸⁷Sr/⁸⁶Sr in the carbonate-rich lake deposits therefore provides a unique means of establishing temporal correlations within lacustrine strata, based on changes in lake water provenance through time.