The stable isotopic compositions of Late Pleistocene and Holocene cave deposits (speleothems) are valuable proxies for
high-resolution climate reconstructions on Earth, in particular with respect to changes in vegetation, temperature,
atmospheric composition, and monsoonal precipitation. On the basis of U-Th dating and annual growth bands,
researchers have shown that many speleothems can grow continuously for thousands to hundreds of thousands of years.
Depending on the growth rate of a given speleothem, and its sensitivity to environmental changes on the surface, it may
record climatic shifts on timescales ranging from weeks to years. This has made modern speleothems particularly useful
for applications ranging from paleotempestology to studies of glacial-interglacial transitions. It stands to reason, then,
that ancient speleothems might hold valuable information about climatic change in the deep geologic past - at
resolutions that have been previously unattainable using other materials (e.g. paleosols). Here we report carbon and
oxygen isotopic signatures obtained from an Early Permian flowstone that was extracted from a shallow paleocave in
Oklahoma. We interpret the stable isotope data to reflect progressive aridification and devegetation, possibly as a result
of CO2 forcing. This interpretation is consistent with independent paleoclimatic data from coeval sediments in the
region, and is also broadly consistent with similar records from modern, low-latitude speleothems. The fact that isotopic
signatures are preserved in speleothems up to a few hundred million years old indicates that it might be possible to
retrieve similar climatic data from ancient carbonate deposits elsewhere in the solar system.