Guidebook 22. Field Trip Guidebook Landforms, Stratigraphy, and Lithologic Characteristics of Glacial Deposits in Central Minnesota

Abstract

This guidebook was prepared for the 50th Midwest Friends of the Pleistocene Field Conference, sponsored by the Minnesota Geological Survey and held at St. John's University on June 4-6, 2004. The purpose of this guidebook is to provide conference participants with an up-to-date general summary of the glacial geology of central Minnesota and a comprehensive reference list of previous research completed in the area. There are a number of reasons why we were motivated to host the Friends of the Pleistocene in central Minnesota. First, over the last 10 years the Minnesota Geological Survey has completed numerous mapping projects in the central Minnesota area (Steams, Pope, and Crow Wing County atlases; the Otter Tail regional hydrogeological assessment; and the USGS Statemap St. Cloud, Baxter, Brainerd, and Gull Lake quadrangle maps), and is in the process of completing mapping projects in Todd, Traverse, and Grant Counties. The large volume of data (samples and descriptions from outcrops and drill holes) collected from these projects has allowed us to evaluate the work done by previous researchers and contribute new insights and interpretations. Second, in 1954 Herb Wright, AI Schneider, and Harold Ameman led the 5th Midwest Friends of the Pleistocene field trip in central Minnesota. We will revisit the area, on this 50th anniversary of that trip, to examine how interpretations have changed and evolved. The guidebook will use a simple, direct approach to summarize the region's glacial geology, similar to that used in 1954. It is our intention to pay tribute to the accomplishments of Herb and AI during the field trip and banquet. We will also acknowledge other researchers who, over the last 50 years, have made contributions to the glacial geology of central Minnesota. Third, we would like to discuss how mapping techniques and technology have changed in the last 50 years. We will examine which techniques have been most effective in understanding the complex stratigraphy of central Minnesota. Finally, field exposures were selected to stimulate interest and discussion about the following glacial topics: erosion, transport, and deposition of source-area materials; processes involved in drumlin formation; the relationship between ice dynamics and glacial landforms; processes important in the formation of the St. Croix moraine; and the challenges of interpreting thick, complex drift stratigraphy. These stops highlight geomorphic features, stratigraphic relationships, and specific unit characteristics (lithology, color, etc.) in an attempt to provide an overview of the glacial geology of this region.