STABLE ISOTOPIC EVIDENCE FOR LATEST PLEISTOCENE AND HOLOCENE CLIMATIC-CHANGE IN NORTH-CENTRAL TEXAS

A paleoclimatic record for a southern Great Plains locality (the Aubre y Clovis site in north-central Texas) has been established using stabl e carbon and oxygen isotopes. Detailed composite stratigraphic section s, constrained by C-14. ages, place the age of these deposits between 14,200 and 1600 yr B.P. Calcium carbonate samples of lacustrine and pe dogenic origin were analyzed. Oxygen isotopic compositions of most of these in situ carbonates reflect equilibrium precipitation from local meteoric waters. Oxygen isotope values reflect changes in the composit ion of meteoric waters tied to changes in the isotopic composition of moisture derived from the Gulf of Mexico. Oxygen isotopic variability at the Aubrey site is coincident with marine isotopic records from the gulf that vary due to changes in Laurentide ice sheet volume and melt water influx. The stable carbon isotopic record, reflecting changing b iomass through time, corroborates humid versus arid interpretations ba sed on sedimentology and rates of alluviation. A middle Holocene arid period was in contrast to moist early and late Holocene climate, affir ming interpretations of other workers studying southern Great Plains H olocene climate history. (C) 1994 University of Washington.