Thickness of Drift and Bedrock Physiography of Indiana North of the Wisconsin Glacial Boundary

Abstract

In recent years ground-water studies have shown that many large aquifers in glacial deposits in Indiana are localized along buried valleys. In these valleys, most of which served as sluiceways at various times during the Pleistocene epoch, large quantities of glacial outwash were deposited. Some of them, such as the Ohio, lower Wabash, and Whitewater, are only partly filled, but other equally large valleys are completely buried. This study is intended primarily to aid in locating the buried valleys within the region of Indiana that is covered by Wisconsin drift and in evaluating them as aquifers. The thickness of drift map should be of interest to geologists, engineers, well drillers, and others who are concerned with appraisal of water resources, cut-outs in coal or limestone, foundation materials for heavy construction, drilling operations, and similar work. In preparing this map an attempt was made to consider carefully the effects of present topographic variations as well as those of the buried surface. The abrupt 50- to 100-foot changes in elevation along present river valleys are shown by closing contour lines. Only in areas of rugged morainal topography where local relief is great and in areas where glacial drift is unusually thick and information is meager are the contours intentionally generalized. These parts of the map undoubtedly will require much revision as additional data become available. Only minor changes should be necessary in most of central Indiana, where water wells that enter bedrock are more abundant.