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

摘要: Oxygen isotope values from lacustrine carbonate in the Laney Member of Green River Formation (Wyoming) exhibit a sudden, basinwide, ~6‰ upsection decrease δ 18 O at ca. 49 Ma. 40 Ar/ 39 Ar geochronology constrains duration isotopic shift to ≤~200,000 years. This change coincides with sudden lake type, balancedfi lled lower LaClede Bed overfi upper Bed, as well an increase proportion calcitic (>80% calcite out total by X-ray diffraction [XRD]) samples 32% 73%. The is correlatable through several locations across Greater Basin, and also previously observed less radiogenic 87