Geomorphic controls on lacustrine isotopic compositions: Evidence from the Laney Member, Green River Formation, Wyoming

Autor:	C. Page Chamberlain, Amalia C. Doebbert, Lauren M. Chetel, Alan R. Carroll, Andreas Mulch
Rok vydání:	2009
Předmět:	Calcite geography geography.geographical_feature_category Radiogenic nuclide Drainage basin Geochemistry Geology Isotopes of oxygen Paleontology chemistry.chemical_compound chemistry Isotopic shift Geochronology Carbonate Green River Formation
Zdroj:	Geological Society of America Bulletin. 122:236-252
ISSN:	1943-2674 0016-7606
DOI:	10.1130/b26522.1
Popis:	Oxygen isotope values from lacustrine carbonate in the Laney Member of the Green River Formation (Wyoming) exhibit a sudden, basinwide, ~6‰ upsection decrease in δ 18 O at ca. 49 Ma. 40 Ar/ 39 Ar geochronology constrains the duration of the isotopic shift to ≤~200,000 years. This change coincides with a sudden change in lake type, from balancedfi lled in the lower LaClede Bed to overfi lled in the upper LaClede Bed, as well as an increase in the proportion of calcitic (>80% calcite out of total carbonate by X-ray diffraction [XRD]) samples from 32% to 73%. The δ 18 O shift is correlatable through several locations across the Greater Green River Basin, and also coincides with a previously observed shift to less radiogenic 87
Databáze:	OpenAIRE
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