STRATIGRAPHY AND PROVENANCE OF THE LATE PLEISTOCENE DEFIANCE MORAINE, SOUTHEASTERN MICHIGAN

The provenance of Late Wisconsinan sediments in the Detroit, Michigan area was studied to determine the history of ice flow associated with the Huron and Erie lobes of the Laurentide ice sheet. Diamicton deposits composing the Defiance Moraine and adjacent Detroit Lowland were characterized by clast counts, and clast suites compared petrographically with those of similar deposits elsewhere in the southern Great Lakes region. The results show that clast suites genetically related to the Huron glacial lobe are characterized by a provenance in the Superior and Southern Provinces, whereas those deposited by the Erie lobe have sources in the Grenville Province, of the Canadian Shield. The Huron lobe clast assemblage was derived primarily from the Paleoproterozoic Huronian Supergroup and Nipissing mafic dike complex, and from greenschist grade Archean basement rocks in the Abitibi Upland, north of Lake Huron. The Erie lobe clast assemblage was probably derived mainly from the Parry Sound, Shawanaga, and adjacent domains of the southeastern Central Gneiss Belt in the Laurentian Highlands north of Toronto. Our data show that the Port Huron-Wyoming, Birmingham, Detroit, Defiance and Ft. Wayne Moraines south of Lake Huron were deposited by the Huron lobe. The St. Thomas, Norwich and Ingersoll Moraines in Ontario, and the Defiance Moraine in northeastern Ohio, are products of Erie lobe sedimentation. In the study area, the stratigraphic section of the Defiance Moraine consists of two depositional sequences, each inferred to be a cycle of glacial advance and retreat. Geomorphic and provenance analyses show that the upper, relatively thin, sequence was deposited as a lateral moraine by the Huron lobe during the Port Bruce phase of the Late Wisconsinan. However, the Defiance Moraine is palimpsest, most of its topographic relief being developed on the buried, thicker lower sequence. The latter is tentatively correlated with the Nissouri phase of the Late Wisconsinan, based on the presence of coal clasts and the fact that the Huron lobe did not erode coal source rocks in the central Michigan Basin during the Port Bruce advance.