Geochronology of late Pleistocene to Holocene speleothemsfrom central Texas: Implications for regional paleoclimate
A detailed chronology for four stalagmites from three central Texas caves separated by as much as 130 km provides a 71 000-yr record of temporal changes in hydrology and climate. Mass spectrometric 238 U230 Th and 235 U231 Pa analyses have yielded 53 ages. The accuracy of the ages and the closedsystem behavior of the speleothems are indicated by interlaboratory comparisons, concordance of 230 Th and 231 Pa ages, and the result that all ages are in correct stratigraphic order. Over the past 71 000 yr, the stalagmites have similar growth histories with alternating periods of relatively rapid and slow growth. The growth rates vary over more than two orders of magnitude, and there were three periods of rapid growth: 71‐60 ka, 39‐33 ka, and 24‐12 ka. These growth-rate shifts correspond in part with global glacial-interglacial climatic shifts. Paleontological evidence indicates that around the Last Glacial Maximum (20 ka), climate in central Texas was cooler and wetter than at present. This wetter interval corresponds with the most recent period of increased growth rates in the speleothems, which is consistent with conditions necessary for speleothem growth. The temporal shift in wetness has been proposed to result