Geomorphic Principles, Soil Patterns, and Glacial History in the Eastern Upper Peninsula of Michigan.
Douglas Wysocki1, Greg Whitney2, Joe Calus2, and Lawrence Carey2. (1) Natural Resource Conservation Service, National Soil Survey Center, 4631 S 50th Street, Lincoln, NE 68516, (2) NRCS, RR 1 BOX 1514C, Manistique, MI 49854
Michigan's eastern Upper Peninsula (UP) is a complex array of glacial landforms and sediments formed directly by glacial ice, or by glacial fluvial and glacial lacustrine processes. Present landforms, surficial deposits, and soil patterns result from the two youngest of several Wisconsin age glacial advances and retreats. These are the Two Rivers (11.8 ka) and Marquette (9.9 ka) advances. The Two Rivers advance extended south into the central Lake Michigan basin. During retreat, the Two Rivers ice margin fronted a large proglacial lake -- Glacial Lake Algonquin. Initially Glacial Lake Algonquin drained southward via the Chicago outlet. Ice retreat from the Mackinaw Straits opened lower elevation outlets to the east. The declining lake stabilized at several levels leaving beach scarps and superposed shore features (e.g., spits, beach ridges) on prior landforms. Major glacial landforms created during the Two Rivers advance and retreat are till-capped bedrock highs along the Niagara escarpment, relict lakebeds, outwash fans and plains, kame moraines, isolated relict islands, and moraines. The Marquette advance, in contrast, reached only the northern edge of the UP, and did not front a glacial lake. Lake Chippewa, a successor to Lake Algonquin, represents a low lake-level phase coincident with the Marquette advance. Major landforms produced during the Marquette advance and retreat are an extensive braided outwash plain through the western part of the Seney Lowland, outwash fans, and a series of ice contact slopes that mark successive ice margins. Both the Two Rivers and Marquette advance overwhelmingly produced glacial fluvial sediments and landforms; true moraines and till are of limited extent. Relict Algonquin shorelines are a key feature for interpreting landforms, sediment origin, and resultant soil patterns. Relict shorelines mark a boundary between subaerial and subaqueous deposition and processes. Furthermore, shorelines cross cut landforms and sediment bodies providing a stratigraphic/geomorphic tool for relative age determination.