In the various geological reports of counties in the Iowan area and of counties through which pass drainage lines from the Iowa area, the Buchanan gravels are classified into two phases: the upland phase and the valley phase. This classification dates back to 1898, when the Report of the Geology of Buchanan County by the late Dr. Samuel Calvin was published by the Iowa Geological Survey. In this report he set forth the conception that the upland gravels were deposited while the valleys were filled with ice and that the gravels in the terraces along the present streams were laid down after the Kansan ice had retreated some distance. In both cases the gravels were regarded by Calvin as Kansan outwash and he called them Buchanan gravels.
Proceedings of the Iowa Academy of Science
©1917 Iowa Academy of Science, Inc.
Leighton, M. M.
"The Buchanan Gravels of Calvin and the Iowan Valley Trains,"
Proceedings of the Iowa Academy of Science, 24(1), 86-86.
Available at: https://scholarworks.uni.edu/pias/vol24/iss1/14