Mj. Chrzastowski et Ta. Thompson, LATE WISCONSINAN AND HOLOCENE GEOLOGIC HISTORY OF THE ILLINOIS-INDIANA COAST OF LAKE-MICHIGAN, Journal of Great Lakes research, 20(1), 1994, pp. 9-26
During the past 14,500 radiocarbon years, southern Lake Michigan has h
ad a complex geologic history. Changes in the locations of accretionar
y and erosional zones accompanied multiple and wide-ranging fluctuatio
ns in lake level. End moraines bordering southern Lake Michigan dammed
the ancestral lake to levels above those that exist now. Along 120 km
of the Illinois-Indiana coast, end moraines are landward from the mod
em lakeshore and rim the Chicago/Calumet lacustrine plain. Where morai
nes intersect the lakeshore, coastal erosion has supplied the littoral
sediment stream. During a series of peak lake levels, the lacustrine
plain was the sink for littoral sediment supplied from the western and
eastern lakeshores. Before about 2.5 ka, this littoral transport term
inated in separate spit systems on opposite ends of former lake embaym
ents. A convergence zone of the western and eastern lakeshore littoral
transport systems formed about 2.5 ka, first near the Illinois-Indian
a state line and then shifting eastward along the Indiana shore. In th
e past 2,000 years, major coastal changes have included southward migr
ation of a beach-ridge plain near the Illinois-Wisconsin state line, e
rosion along the Chicago central lakeshore, and erosion in the vicinit
y of the Illinois-Indiana state line. Coastal erosion along the centra
l Chicago lakeshore apparently played a major role in developing the m
odem drainage pattern of the Chicago River.