The rock formations of Linn County belong to the Devonian period. During an examination with the possible exploitation of Devonian rock as a source of Portland Cement, Mr. A. S. Hammond and others of Cedar Rapids, Iowa, encountered in an excavation near Palo, Iowa, a black, bituminous shale. The shale is fine-grained and in places very bituminous. The layers vary in thickness from mere seams along bedding planes to an inch in thickness where exposed in the excavation, and lie at various depths below the surface in the valley of Little Bear creek. The presence of an old shaft sunk by farmers with the possible finding of coal in view, led to further exploration, of which this is a report.
Proceedings of the Iowa Academy of Science
©1923 Iowa Academy of Science, Inc.
Dille, Glenn S.
"Notes on the Occurrence of a Black Bituminous Shale near Palo, Linn County, Iowa,"
Proceedings of the Iowa Academy of Science, 30(1), 441-443.
Available at: https://scholarworks.uni.edu/pias/vol30/iss1/70