cenvironmental history  

introduction geography geology cultures ecosystem conservation  

Project goal:  Help sustain the natural resources and protect cultural resources of the Driftless Area.

geography and biogeography
Driftless Area


The Driftless Area is a bedrock plateau that includes 24,000 square miles in the hilly region covering the corners of Minnesota, Wisconsin, Illinois, and Iowa. The region is named the Driftless Area because the glaciers of the Pleistocene Ice Age did not deposit large quantities of a type of sediment known as drift over the hilly region. Thick deposits of drift were deposited in the flat areas of Minnesota, Wisconsin, Illinois, and Iowa. The Driftless Area is a relatively rural area with a mixture of agricultural fields and forest patches (see photograph above). Click on the map above right for more maps of the Driftless Area.    
The erosion by the continental ice sheets of the Pleistocene epoch deposited thick layers of coarse sediments, gravel, and boulders known as glacial drift outside of the Driftless Area as the ice sheets melted and retreated back to the polar region. The very fine grain sediments from the drift were picked up in the wind and deposited on the landscape.  These fine grain wind blown deposits are known as losses.  The hard parts of organisms living in the tundra and boreal habitats of the Pleistocene epoch were buried in the thick loss deposits. Fossils in the losses deposits can be used to help reconstruct environmental conditions. Some of the fossil land snail species have been discovered as living species on the slopes of the Driftess Area, because of the modern cold climate conditions on the slopes are similar to conditions in front of the ice sheets during the Pleistocene epoch.  These land snails are thought to have colonized the Driftless Area during the late Pleistocene epoch and early Holocene epoch as a cold climate refugia when the last ice sheets retreated and the climate became warmer (USFWS, 1983). It is thought that live land snails can become attached to the bodies of birds and mammals or ingested by birds and mammals to be excreted later that allow them to colonize distance places.  Click on the map to the right for more maps for the various advances of the continental ice sheets of the Ice Ages during the Pleistocene Epoch.

U.S. Fish and Wildlife Service (USFWS).  (1984).  National recovery pland for the Iowa Pleistocene snail (Discus macclintocki (Baker)).  Prepared by Terrence J. Frest, Department of Geology, University of Iowa, Iowa City, Iowa.   
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