58-13 A SERIES OF SITES IN INNER SPACE CAVERN ON THE EDWARDS PLATEAU, TEXAS, DOCUMENT VERTEBRATE DIVERSITY FROM WARM (MIS 3) AND COOL (MIS 2) INTERVALS OF THE LATE PLEISTOCENE.

Session: Future Leaders in Paleontology

Presenting Author:

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Abstract:

Most Late Pleistocene sites in North America span a short interval of geologic time and date to the latter part of Marine Isotope Stage (MIS) 2. The Edwards Plateau of central Texas boasts a rich record of sites dating to the Last Glacial Maximum and younger, but records of earlier warm intervals, MIS 3 and MIS 5, are unknown in the region with that bias limiting understanding of faunal dynamics leading up to the extinctions at the end of epoch. Inner Space Cavern (ISC), a show cave in Williamson County, Texas, may be an exception. Radiocarbon and faunal data collected in the 1960s indicated that four talus or debris cones in ISC formed asynchronously throughout the Late Pleistocene, preserve different vertebrate taxa, and may together document faunal change across the glacial-interglacial cycle. I tested those hypotheses by conducting excavations at five sites throughout ISC and used the resulting samples to document faunal composition and develop a chronology. Collagen was absent from all fossils, but radiocarbon ages on charcoal, bioapatite, and organic sediment indicated that three adjacent sites in ISC were broadly contemporaneous. Debris Cones 2 and 3 both spanned from MIS 3 (~46 and ~47 ka) to MIS 2 (~16 ka) and Debris Cone 2 extended into the early Holocene (~9.5 ka). Bat Breakdown, a newly discovered site, was a subset of that interval, ranging from ~31.5 to ~29 ka. The three sites also contained a broadly similar fossil fauna, with the faunal distinctions observed in previous investigations now attributable to sample bias. Megalonyx sp. and large Antilocapridae were absent from Last Glacial Maximum or younger deposits in ISC, a pattern reflected elsewhere in the region. The new data show that sites in ISC provide a rare example of a long, multi-millennial Late Pleistocene record, including the only known regional evidence of the fauna of MIS 3, establishing the framework necessary to test hypotheses about faunal change across the glacial-interglacial cycle.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9844

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