Abstract
Chemical sediments of the lacustrine Wilkins Peak Member of the Eocene Green River Formation potentially preserve detailed paleoclimate information relating to the conditions of their formation and preservation within the lake basin during the Early Eocene Climatic Optimum. The Green River Formation comprises the world's largest sodium-carbonate evaporite deposit in the form of trona (Na2CO3⋅NaHCO3⋅2H2O) in the Bridger Basin and nahcolite (NaHCO3) in the neighboring Piceance Creek Basin. Modern analogues suggest that these minerals necessitate the existence of an alkaline source water. Detrital provenance geochronometers suggest that the most likely source for volcanic waters to the Greater Green River Basin is the Colorado Mineral Belt, connected to the basin via the Aspen paleoriver. Here, we test the hypothesis that magmatic waters from the Colorado Mineral Belt could have supplied the Greater Green River Basin with the alkalinity needed to precipitate sodium-carbonate evaporites that are preserved in the Wilkins Peak Member by numerically simulating the evaporation of modern soda spring waters from northwestern Colorado at various temperature and atmospheric pCO2 conditions. The resulting simulated evaporite sequence is then compared to the mineralogy and textures preserved within the Wilkins Peak Member. Simulated evaporation of Steamboat Springs and Mineral Spring waters produce a close match to core observations and mineralogy. These simulations provide constraints on the salinities at which various minerals precipitated in the Wilkins Peak Member as well as insights into the regional temperature (>15 °C for gaylussite and trona; >27° for pirssonite and trona) and pCO2 conditions (<1200 ppm for gaylussite and trona) during the Early Eocene Climatic Optimum.
Original language | English (US) |
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Article number | 105597 |
Journal | Applied Geochemistry |
Volume | 151 |
DOIs | |
State | Published - Apr 2023 |
Bibliographical note
Funding Information:We thank Matteo Paperini and Solvay Chemicals, Inc. for their contribution of the Solvay S-34-1 core. We thank Robert V. Demicco for his insights and expertise in modeling carbonate and evaporite deposition. We thank the staff at LacCore National Lacustrine Core Facility at the University of Minnesota, Minneapolis for processing and storage of the core: Kristina Brady Shannon, Anders Noren, Ryan O'Grady, Amy Myrbo, Mark Shapley, Alex Stone and Jessica Heck. We gratefully acknowledge Andrew Walters, Shlomo Honig, Isaac Sageman, for their assistance in the preparation, imaging, and logging of the core. We thank David Tuttle for core and thin section photomicrographs reproduced in this manuscript. This study received financial support from the National Science Foundation Integrated Earth Systems Program (NSF-EAR 1812741; NSF-EAR 1813278; NSF-EAR 1813350).
Funding Information:
We thank Matteo Paperini and Solvay Chemicals, Inc. for their contribution of the Solvay S-34-1 core. We thank Robert V. Demicco for his insights and expertise in modeling carbonate and evaporite deposition. We thank the staff at LacCore National Lacustrine Core Facility at the University of Minnesota, Minneapolis for processing and storage of the core: Kristina Brady Shannon, Anders Noren, Ryan O'Grady, Amy Myrbo, Mark Shapley, Alex Stone and Jessica Heck. We gratefully acknowledge Andrew Walters, Shlomo Honig, Isaac Sageman, for their assistance in the preparation, imaging, and logging of the core. We thank David Tuttle for core and thin section photomicrographs reproduced in this manuscript. This study received financial support from the National Science Foundation Integrated Earth Systems Program ( NSF - EAR 1812741 ; NSF - EAR 1813278 ; NSF - EAR 1813350 ).
Publisher Copyright:
© 2023 Elsevier Ltd
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