Lineaments and fracture traces, Jennings County and Jefferson Proving Ground, Indiana

Abstract

Jennings and several adjacent counties are economically restricted "by inadequate water supplies. The North Vernon Water Utility, supplying more than 25 percent of Jennings County's population, obtains its water from the Vernon Fork Muscatatuck River, although streamflow is less than the average daily withdrawal 69 days of the year. The U.S. Army, Jefferson Proving Ground, pipes water more than 5 miles and lifts it 375 feet for fire protection. Another Jennings County utility pipes water more than 15 miles to rural domestic consumers unable to locate sufficient ground-water supplies. Two nearly horizontal sequences of Paleozoic limestone and dolomite, intermittently separated by a thin, discontinuous shale unit, constitute the principal aquifer. Many wells tapping this aquifer are unable to supply single-dwelling needs, whereas others supply several dwellings with ease. All the wells tapping the aquifer have been located for the owners' convenience and are randomly located in relation to lineaments and fracture traces. Lineaments and fracture traces were observed throughout the study area, and those most easily interpreted are shown on a map at a scale of 1:48,000. Pleistocene drift, averaging 25-30 feet thick, covers most of the bedrock, but did not restrict the mapping of lineaments and fracture traces from aerial photographs. The lineament and fracture-trace map indicates probable locations of vertical or near vertical fractures in the bedrock. Wells drilled on these mapped features may yield adequate supplies for domestic use. Larger yields may be available in several areas of southwest Jennings County where lineaments parallel major stream channels. Well placement is important in this area, as fractures are a principal source of water to wells. In areas of fractured bedrock, the most productive well locations are at the intersections of two or more mapped lineaments or fracture traces and at the lowest local altitude. Use of the lineament and fracture-trace map will not guarantee a sufficent supply of ground water but will minimize the chance of drilling an inadequate well.