The Kentland Area of Disturbed Ordovician Rocks in Northwestern Indiana
In the southern part of Newton County, in the northwestern part of Indiana, strata of Middle Ordovician (St. Peter, Black River, Galena) age are exposed at the surface, surrounded on all sides, so far as is known, at lower elevations by younger strata. The exposed beds have been uplifted vertically about 1,500 feet and now exhibit very high dips, in some cases being vertical or even overturned. The disturbed area, so far as its limits are at present known, covers less than one square mile and exhibits both folding and faulting; the latter phenomenon being the common way in which the rock failed under stress. A Middle Ordovician sequence of about 400 feet of dolomites, limestones, sandstones, and shales, containing a fauna of over seventy-five species, is involved in the deformation and exhibited at the surface. The present structural conditions appear to have resulted from "cryptovolcanic" activity.