STABLE ISOTOPIC AND TRACE-METAL RECORDS FROM TWO TRAVERTINE LOCATIONS IN KENTUCKY

Drainage dissection of karstified limestone bedrock over large portions of central and western Kentucky provides opportunities for travertine formation.  Traditionally, geochemical signatures preserved in travertine deposits yield unique insights for defining episodes of local and regional paleohydrologic change.  The present study seeks to construct geochemical records of paleohydrologic variability preserved in travertine deposits from Fayette County (central Bluegrass Plateau) and Hart County (upper-middle Green River Basin), Kentucky, and to define the records in a geochronological context using U-series dating methods.  Travertine from southeast Fayette County (Lexington Area) is formed from ground waters that emanate from a shallow karst aquifer in Ordovician limestone.  Preliminary isotopic results from a drilled transect through a travertine dripstone from Fayette County indicate a range in d¹³C of 3.4‰ (-2.3‰ to –5.7‰ vs. VPDB) and a range in d¹⁸O of 1.1‰ (-4.4‰ to –5.5‰ vs. VPDB).  Travertine from Hart County, ~100 miles to the southeast of Lexington, is formed from ground waters that emanate from a shallow karst aquifer in Mississippian limestone.  The oxygen isotopic record from the Fayette/Hart County travertine is expected to be representative of carbonate that precipitates in equilibrium with typical Bluegrass/Green River precipitation, respectively.  Outcomes of the present study will be synthesized with results of previous and ongoing studies from cave and lacustrine deposits in the region in order to provide a spatially- and temporally-resolved record of paleohydrologic and paleoclimatic change for a critical portion of the Interior Lowland Plateau of eastern North America.