Late Pleistocene and Holocene faunal and environmental changes at Hall's Cave, Kerr County, Texas




Toomey, Rickard Stanley, 1963-

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Hall's Cave contains 3.7 meters of well-stratified, bone-bearing, elastic sediments. Eleven radiocarbon determinations provide good temporal control and indicate that deposition occurred fairly continuously over least the past 15,000 years. These sediments contain abundant, well-preserved vertebrate remains that reflect the changing central Texas faunas through the latest Pleistocene and Holocene. Hall's Cave contains the remains of at least 62 species of mammals and at least 48 species of non-mammals. The fauna includes at least 12 extinct (one turtle, 3 birds, and 8 mammals) and 22 extralimital taxa. The paleoenvironmental study of the fauna includes the analysis of climatic tolerance of important taxa based on their geographic ranges. During the Last Glacial Maximum, the central Texas climate was cooler and moister than modern. Mean annual temperature was probably 5°C or more cooler, and summer temperatures were at least 2°C cooler. Effective moisture was higher in all seasons and precipitation was probably higher in the summer. The eastern and central Edwards Plateau was covered with a deep red soil that supported a diverse grassland community. Between 14,500 and 12,500 RCYBP rapid warming and possibly drying occurred. This resulted in the extirpation of several cool and/or mesic adapted species. By 12,500 the temperature of the Edwards Plateau may have been close to modern conditions. The drying was part of gradual trend of decreasing moisture that peaked at approximately 3500 RCYBP. Several more mesic intervals, approximately 10,400 to 9000 RCYBP and approximately 2500 to 1000 RCYBP, interrupted the general drying trend. After 1000 RCYBP drying conditions resumed. Gradual down-wasting of the soils accompanied the drying and resulted in decreasing soil depths. This soil loss led to the extirpation of numerous burrowing taxa. Throughout the interval the western Kerr County area was covered with an open vegetation, probably a grassland or open savanna.