Geology of the Grand Calumet River Region

The geology of the Calumet River region is briefly reviewed to provide a background fo r applied research in the area . The review relies heavily upon research conducted by scientists affiliated with the Indiana and Illinois Geological Surveys . At the end of the Late Wisconsinan glacial epoch , fluctuations in the Lake Michigan Lobe of the Laurentide Ice Sheet resulted in the formation of three moraine systems around the south end of the Lake Michigan basin : in decreasing age, the Valparaiso, Tinley and Lake Border ridges . High stands of ancestral Lake Michigan (also known as glacial Lak e Chicago) are named the Glenwood, Calumet and Algonquin high phases that formed when the north en d of the basin was blocked by ice . Retreat of the glacier from the basin caused the lake level to drop durin g the Two Creek low phase . The Chippewa low occurred at the beginning of the Holocene when ancestra l Lake Michigan was as much as 107 m below modern levels . Lake level then rose in response to isostati c rebound of the outlet in southern Ontario until the Nipissing high was reached about 5000 years ago . A t this time, the Toleston Beach in northern Indiana and Illinois was developing as a complex of sand dune s and more than 100 beach ridges . The Grand Calumet River came into existence about 2600 years ago a s spits deflected the Little Calumet River eastwards upon closure of the Sag channel . Eastward migratio n of the Grand Calumet River ceased when the coastline was modified following European settlement i n the late 19th century .