Microfossils in Wisconsinan Loess and Till from Western Illinois and Eastern Iowa

Wisconsinan loess from Illinois and Iowa contains a varied assemblage of microfossils including radiolaria, foraminifera, sponge spicules, and opal phytoliths. The foraminifera and radiolaria are derived from Cretaceous rocks occurring on the northern Great Plains. The sponge spicules are from fresh-water sponges living during the epoch of loess deposition. The phytoliths were produced by vegetation growing during deposition. These microfossils are valuable in determining loess and till provenance and in paleoecological reconstruction.