QUATERNARY LITHOSTRATIGRAPHY OF MINNESOTA

The Minnesota Geological Survey will soon be publishing a report entitled, The Quaternary Lithostratigraphy of Minnesota. A working group has identified 113 lithostratigraphic units that have been, or are, in use in the state. The report will consist of an introduction that outlines the framework for identifying and defining formal units, followed by a series of appendices that define (or redefine) the various units. Each unit will be defined in an appendix, and each appendix will include name and rank of the unit, the geographic source of the name, the location and description of type and reference sections, a lithologic description of the unit, a description of the upper and lower boundaries, a historical background to the unit and the use of its name, the dimensions, shape, and geographic distribution of the unit, the differentiation from other units, the absolute age of the unit (if known), and the correlation to other units. In our report, 18 currently formal units are accepted and recognized (for example, the Gervais and Loveland Formations, and the Sunrise Member of the Cromwell Formation), 43 units will be newly defined and formalized (for example, the Aitkin, Brainerd, and Hewitt Formations), 18 units of informal and currently formal status will be discontinued (for example the Arsenal Sand, the Fridley Formation, and the Lake Agassiz Clays), and 8 currently formal units will be modified (for example, the Independence Formation, the Twin Cities Member of the New Ulm Formation, and the Wrenshall Member of the Barnum Formation). A remaining 26 units will be not acted upon at the present time and include many units from Southwest Minnesota Regional Assessment project, as well as units in regions being mapped currently or in the near future. The purpose of this poster presentation is to inform the geologic community of our working group and to solicit help and commentary. The redefined lithostratigraphy of Minnesota is one that we hope will be of continued use to geologists, soil scientists, and engineers. As new units are discovered, and as modifications of unit definitions are required, the survey will publish supplements to the lithostratigraphy of Minnesota.