Figure 14
Correlation of Dempsey Divide habitation events with
the Holocene fossil shrew record from Hall's Cave on the Edwards Plateau of
central Texas. These two species have opposite moisture requirements, and their
alternating dominance over time records long-term fluctuations in effective
precipitation on the Southern Plains. Note that each of the major occupations of
the Dempsey Divide coincides with a period of greater effective precipitation as
indicated by the Hall's Cave record. The long drought of the Altithermal stands
out above all else. Pond and marsh deposits accumulated in the upland valleys of
the Dempsey Divide from Late Pleistocene times until about 9,000-8,000 years
ago. Deep canyons were eroded in these valleys during the Altithermal, and began
rapidly refilling with dry sediment around 3300 years ago. Adapted from Toomey et
al. 1993: Figure 6.