Geology as a Contribution to Land Use Planning in LaPorte County, Indiana

Abstract

LaPorte County, in northwestern Indiana, is in a geologically complex region underlain at shallow depths by depositional sequences of glacial till, outwash sand and gravel, and lacustrine silt and clay. The combined agents of ice, wind, and water have sculptured these deposits into a topographically varied landscape ranging from sandy flats of the Kankakee Outwash and Lacustrine Plain to partly wooded hilly uplands on the Valparaiso Moraine. Beneath the glacial materials, which range from 25 to 350 feet in thickness, is a sequence of Paleozoic rocks that is about 4,000 feet thick. Limestone, dolomite, sandstone, and shale, complexly interlayered and varying in thickness, make up the bedrock units, which provide ground water potential and contain potentially commercial deposits of gypsum near LaPorte. Most of the environmental geologic factors are dependent on the thickness, continuity, and physical properties of the unconsolidated deposits that make up the surface of the county. The texture, mineralogy, and depositional origin of these sediments largely determine their engineering properties and subsequent suitability for sanitary landfilling, septic systems, and construction. The availability, quantity, and quality of ground water also depend on the geologic properties of the unconsolidated glacial deposits and on the underlying bedrock formations. Ground water, discussed in this report, is abundant throughout much of LaPorte County because of porous and permeable sand and gravel deposits. Besides the indirect applications of geology to environment, some earth materials have commercial value in their own right. Sand and gravel, clay, peat and marl, and gypsum and anhydrite are valuable commodities that may be extracted from glacial drift or bedrock.