Evidence for an abrupt latest Miocene-earliest Pliocene climate shift preserved in a sinkhole paleolake at the Gray Fossil Site, northeastern Tennessee (Washington County)

Records of Neogene terrestrial climate are rare for the eastern half of North America. The recently discovered Gray Fossil Site (GFS) in northeastern Tennessee (Washington County) appears to be a sinkhole paleolake that preserves such a record. Well-preserved vertebrate GFS fossils strongly suggest a Late Miocene-Early Pliocene (Hemphillian) Land Mammal Age (2:. 4.5 Ma). Three distinct facies occur within the upper 20 m of GFS lacustrine sediment. The graded facies is characterized by continuous succession of individual graded beds that average 0.8 cm thick. This facies contains < I% total organic carbon (TOC), has carbon isotope composition (613C V-PDB) averaging-25.4%0 with values as positive as -24.3%o, and is interpreted to represent deposition from sporadic storm events in a water-stressed ecosystem. The laminated facies overlies the graded facies. The transition between the two facies is marked by: I) the development of a depositional pattern that grades into the laminated facies, 2) an abrupt increase from