Regionalization of Indiana

Abstract

ESPITE Indiana's small area (about 36,000 sq. miles) and slight range in elevation (313 to 1285 feet, with about four-fifths within 650 to 1,000 feet), there is sufficient areal contrast so that a number of regions are generally recognized. Detailed studies divide the state into four to twelve regions, and there are logical bases for additional sub-divisions. Here numerous bases for regionalization are considered, maps are given which locate the regions, and some boundary lines are discussed. As Indiana is a fairly representative state, some of the bases and methods found useful here may have suggestive value to persons interested in the regionalization of other areas. The several subdivisions of Indiana on each of 16 bases are characterized. A composite, or compromise, of the 16 sets of regions is proposed and briefly described. Indiana has been divided into regions by several types of investigators, each considering different criteria, Geologists, for example, have mapped the rock formations. Their findings may be summarized regionally as shown in Figure 1. 1) Southeastern Indiana has a succession of strata of early Paleozoic age which dip gently westward. These rocks are chiefly limestones and shales, which have yielded many fossils but almost no mineral wealth except crushed limestone and materials for lime and cement. None of these rocks are sufficiently resistant to erosion to form conspicuous features of the landscape. 2) South-central Indiana has a succession of shales, limestone, and sandstones of Mississippian age. Some of the sandstones make high hills while the chief limestone yields the well-known Indiana oolitic building stone. These rocks also dip westward. 3) Southwestern Indiana is underlain by rocks of Pennsylvanian age, including several coal beds which are locally mined. Immediately beneath the coals are soft shales, some of which are locally used for fire brick, tile, or common brick. Farther below the coals are sandstones, some of which locally contain oil and gas. 4) Most of central and northern Indiana are underlain by almost horizontal limestones and shales, chiefly of Silurian age, but these rocks are nearly everywhere deeply covered by glacial till. They are locally quarried for crushed rock and for materials from which cement and rock wool are made. The glacial deposits of Indiana are subdivided by geologists into those of the Illinoian Ice-sheet, found locally in southeastern and southwestern Indiana; those of the Early Wisconsin Ice-sheet, found throughout most of central Indiana; and those of the Late Wisconsin Ice-sheet, found in northern Indiana.