Ages and stable isotope ratios from speleothem calcite from Cold Water Cave, Iowa

High-precision uranium-thorium mass spectrometric chronology and 18O-13C isotopic analysis of speleothem calcite from Cold Water Cave in northeast Iowa have been used to chart mid-Holocene climate change. Significant shifts in d18O and d13C isotopic values coincide with well-documented Holocene vegetation changes. Temperature estimates based on 18O/16O ratios suggest that the climate warmed rapidly by about 3°C at 5900 years before present and then cooled by 4°C at 3600 years before present. Initiation of a gradual increase in ?d13C at 5900 years before present suggests that turnover of the forest soil biomass was slow and that equilibrium with prairie vegetation was not attained by 3600 years before present.