21. Coal measures
Nearly all of Poweshiek County is covered by loess and drift to such a depth that little is known concerning the underlying stratified formations. Almost the only natural exposures of rock in the county are in the southwestern part where there are frequent outcroppings of Saint Louis limestone and Coal Measure strata; for the remainder of the county the only data obtainable are from wells sunk in various places. From these it appears that the northern, middle and eastern portions of the county are underlaid immediately below the drift with Lower Carboniferous strata. The Saint Louis limestone was found at Grinnell a little over 200 feet from the surface, while a little farther east the drift is still thicker with no indication of shale or coal. Coal has been found in paying quantities a few miles west of the county line in Jasper County at the Black Oak mine, and also a short distance from the south county line at the Evans mine. A direct line drawn from one of these mines to the other would cut across a considerable part of the southwestern corner of Poweshiek County. At Thornburg also, not far from the southeast boundary, coal mines are being operated. But although coal has been found on both sides so near, few workable veins have yet been found within the county limits.
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
Jones, Arthur J.
"Coal Measures of Poweshiek County,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 59-60.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/22