Glacial drift in Illinois : thickness and character

Abstract

Unconsolidated deposits-mainly glacial drift-over lie bedrock and form the land surface in most of Illinois.These unconsolidated deposits , consisting of various sed iments transported by ic e, wind, and water, are parent ma terials for most Illinois soils, are important sources of build ing products and ground water, and affect land use, mining, construction , and drilling operations .As shown by the drift thickne ss map of the state in cluded in the report, glacial drift ranges from less than a few feet to about 600 feet thick.The thickest drift occurs over major valleys cut into bedrock and, regionally, in the northeastern quarter of the state.The thinnest drift-less than 5 0 feet thick and intersected by numerous bedrock out crops-occurs widely in southern and western Illinois.