RI-68 Quaternary Lithostratigraphic Units of Minnesota

Abstract

Much of Minnesota is covered by sediment of Quaternary age that was deposited during numerous glaciations by ice, wind, and water. In this report, we follow guidelines of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 2005) to create a framework for establishing formal lithostratigraphic units in Minnesota. We evaluate over 100 lithostratigraphic units that have been identified in Minnesota. Eighty (80) units are considered to be useful lithostratigraphic units of formation and member rank, and these are formally accepted in this report or are recommended to be so in future publications. These 80 units include previously named formal lithostratigraphic units that are recognized and accepted as originally defined, but also formally defined units that we have revised or redefined to better fit into our stratigraphic framework. The remaining lithostratigraphic units have been used informally in earlier reports or are newly named in this report.

Additional units that are no longer considered necessary as lithostratigraphic units are abandoned in this report. These units include previously used units of both formal and informal status.

Of the 80 lithostratigraphic units recommended to be retained, 47 are formally defined, revised, or redefined in this report. The remaining 33 units are recommended to be formally named in a future Minnesota Geological Survey Report of Investigations.