Significant New Exposures of Pleistocene Deposits at Kirwin, Phillips County, Kansas

Abstract

A cut-off trench excavated in 1953 by the U. S. Bureau of Reclamation at Kirwin, Phillips County, Kansas, has provided hitherto unavailable data on the Pleistocene deposits of the North Fork Solomon River Valley. The excavations cross approximately 1 mile of high terrace and reveal an abandoned and filled valley cut in Cretaceous chalks and shales. The Pleistocene deposits are classed as Grand Island and Sappa (including the Pearlette volcanic ash bed) members of the Meade formation, of Kansan age, marked in the top by the Yarmouth buried soil; the Crete-Loveland member of the Sanborn formation of Illinoian age, marked in the top by the Sangamon buried soil; and the Peoria silt member of the Sanborn formation of early Wisconsinan age. Molluscan faunas are listed from the Grand Island, Sappa, Crete-Loveland, and Peoria. These exposures show that the bedrock valley had been cut to a level below the present flood plain before deposition of the Kansan sediments.