Page 7 - DesMoinesRiver

Since the end of the Pleistocene Landform regions of Iowa. contributions to our knowledge of what the late
erosional and depositional Ice Age environment was like in this portion of
processes have erased or sloths, giant armadillos, mastodons, and four the state.
buried many of the surface species of mammoth. Beginning in 2012 excava-
features left by the glaciers. tions near the town of Oskaloosa, Iowa have The end of the Pleistocene epoch is marked by
These processes created the produced fossil remains of both Columbian and the retreat of the last continental glacier around
steeply rolling landscape and Wooly mammoths. Radiocarbon dates and the 11,000 years ago ushering in the modern pe-
well-established drainage divides identification of plant remains found in asso- riod known as the Holocene epoch. The Early
that characterize the region today. ciation with these bones will make significant
Geologists refer to this land-
scape as the Southern Iowa
Drift Plain (Tassier-Surine
2004:51–52). Loess is found
throughout the region and is
often exposed along creek and
river banks. In some locations
it is as much as eight feet thick.

During the Pleistocene, southern
Iowa was likely several degrees
cooler on average than today. Spruce and
larch were the dominant trees in the eastern
two thirds of the state (Baker et al. 1990;
Peterson and Wendt 1999:4). Paleontolo-
gists have identified 88 taxa of Pleistocene
mammals in the state. Many of these creatures
are still extant, having adapted to the changing
climate or migrated to more suitable environ-
ments. Most of the distinctive giant megafauna
that are often associated with the Ice Age,
however, have become extinct. Late Pleistocene
megafauna whose remains have been found in
Iowa include giant beavers weighing up to 300
pounds, the American lion, giant short-faced
bear, muskox, two species of giant ground

The University of Iowa Off ice of the State Archaeologist 7