Correlation of the Waldron and Mississinewa Formations

Abstract

Silurian and Devonian outcrops of Indiana are divided roughly into two areas, northern and southeastern Indiana. The bedrock of the northern area is largely covered by glacial drift, whereas the bedrock of the southeastern area is well exposed. These two areas are separated by an intervening zone which is blanketed completely by glacial drift. Although accurate and detailed work has been done on the Silurian and Devonian outcrops of the state, the formations of the two areas have never been correlated. The Silurian and Devonian formations in Indiana dip off the Cincinnati and Kankakee Arches into the Michigan Basin and the Eastern Interior Basin. The formations are difficult to trace in subsurface studies, because they are composed of a series of gradational limestones, dolomites, and calcareous siltstones. The surface formations have not been recognized in the subsurface strata. Some of the subsurface beds cannot be correlated with the outcropping beds, because additional sediments deposited in the basin do not appear on the arches.

The Silurian-Devonian contact lacks identifying characteristics over much of the area, and, for this reason, many subsurface reports have considered both systems as one unit. The writers believe that accurate determinations of thickening, thinning, and pinching-out of the Silurian and Devonian formations on the flanks of the arches would be of great assistance in future prospecting for oil.

These two problems, the geology of the arches and the geology of the basins, go hand in hand. Additional subsurface correlation studies are needed to clarify the Silurian and Devonian stratigraphy of Indiana.