Date of Award
Master of Arts (MA)
This study is a reconnaissance of the surficial geology and a reconstruction of the late Cenozoic history of an area in westcentral Minnesota. The study area extends eastward from the Comstock area (14 miles south of Moorhead, Minnesota) in the Red River Valley to the Sebeka area (13 miles north of Wadena, Minnesota). The area is about 27 kilometres wide and 140 kilometres long.
Surface materials include Pleistocene glacial sediment and Pleistocene and Holocene fluvial, lacustrine, eolian, and bog sediment.
Four geomorphic districts are recognized. The flat Lake-Plain District is underlain by sand, silt, and clay that was deposited as offshore sediment in the Lake Agassiz basin in Early Holocene time. The flat to rolling Shoreline-Complex District is underlain largely by lacustrine shoreline sand and gravel. The district includes the complex network of beach ridges and wave-cut scarps that were developed at the margin of Lake Agassiz in Late Wisconsinan and Early Holocene time. The gently undulating to strongly rolling Glacial-Upland District is underlain by glacial and fluvial sediment that varies in age from pre-Wisconsinan to Late Wisconsinan. Topography characteristic of subglacial smoothing and the collapse of englacial.and superglacial debris, as well as meltwater channels, eskers, and esker complexes are characteristic types of morphology present in the district. The Outwash District is underlain largely by sand and gravel that was deposited by rivers that flowed on top of and from melting glacier ice. The characteristic morphology of the district includes collapsed outwash topography and pitted outwash plains.
The deposits of four glacial events form four lithostratigraphic units-that are recognized at the surface in the study area. The units, which are characterized by distinctive texture and lithology of the very-coarse-sand fraction of the glacial pebble-loam, are readily recognized in the field by differences in color, structure, and texture.
The pre-Wisconsinan or Early Wisconsinan Sebeka Formation, Early Wisconsinan New York Mills Formation, Late Wisconsinan Dunvilla Formation, and Late Wisconsinan Barnesville Formation were deposited by advances of glacial ice that came from the northeast, due north, northwest, and northwest respectively. All but the Barnesville Formation correlate with other lithostratigraphic units in northwestern Minnesota and northeastern North Dakota.
Anderson, Curtis A., "Pleistocene geology of the Comstock-Sebeka area, west-central Minnesota" (1976). Theses and Dissertations. 3.