Capture of high-altitude precipitation by a low-altitude Eocene lake, Western U.S

• Published in: Geology (Boulder) 2008-10, Vol.36 (10), p.791-794
• Main Authors: Carroll, Alan R, Doebbert, Amalia C, Booth, Amanda L, Chamberlain, C. Page, Rhodes-Carson, Meredith K, Smith, M. Elliot, Johnson, Clark M, Beard, Brian L
• Format: Article
• Language: English
• Subjects: basins; Cartography; Cenozoic; clastic rocks; deltaic environment; depositional environment; Drainage; drainage patterns; elevation; Eocene; Estimates; Freshwater; geochemistry; Green River Formation; Idaho; intermontane basins; isotope ratios; isotopes; LaClede Bed; lacustrine environment; Lake Gosiute; Laney Shale Member; Laramide Orogeny; middle Eocene; mudstone; O-18/O-16; oxygen; Paleogene; paleogeography; paleohydrology; paleolakes; paleolimnology; paleorivers; Rivers; sandstone; Sedimentary geology; sedimentary rocks; stable isotopes; Stratigraphy; Tertiary; United States; Western U.S; Wyoming
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/G24783A.1

Sedimentary facies of the Eocene Green River Formation reflect a rapid increase in water supply to Lake Gosiute ca. 49 Ma, marked by a stratigraphic fill-to-spill surface. Deposits below this surface constitute repetitive lacustrine expansion-desiccation cycles, whereas those above consist of continuous profundal lacustrine mudstone, grading upward into volcaniclastic deltaic sandstone. Above the fill-to-spill surface, calcitic mudstone δ18O decreases from approximately +26 per mil to +20 per mil over an interval representing approximately 100 k.y. We interpret this shift to have resulted from capture of a foreland river (or rivers) that drained higher topography north of Lake Gosiute, most likely in north-central Idaho. Accurate paleoelevation estimates derived from stable isotopic records in intermontane basins thus may require detailed knowledge of regional drainage systems.