Windrow Formation of Upper Mississippi Valley Region a Sedimentary and Stratigraphic Study

Abstract

The Windrow formation consists of deposits of iron oxide and siliceous gravel with associated grit, sand, and clay occurring on the uplands of the Driftless Area of Wisconsin and adjacent glaciated portions of Minnesota and Iowa. The formation may be conveniently divided into two members: the older, or Iron Hill, member consisting of iron oxide replacement deposits, and the younger, or East Bluff, member representing the clastic facies. The stratigraphic relations of the Windrow formation indicate a post-Devonian, pre-Pleistocene age, but precise dating is difficult because of the almost total absence of contemporaneous faunal and floral remains. Lithologic and mineralogic studies, however, indicate that the formation is correlative to certain basal Cretaceous deposits in south-central Minnesota and western Iowa. It seems probable that the Iron Hill member was deposited as a result of reaction of iron-charged waters with carbonate bedrock. The East Bluff member shows a number of unique lithologic features...