REVISITING THE RED BED PROBLEM IN THE MICHIGAN BASIN: MORE COMPLICATED THAN YOU'D THINK

Study of Michigan's late Paleozoic and Mesozoic stratigraphy is complicated by limited exposures, overgrown quarries, and limited subsurface samples to study. Three distinct stratigraphic red beds units appear to be present in the Lower Peninsula of Michigan. Information has been discerned from examination of documents, historic photographs, historic mine and quarry sites, outcrops, and some core samples. The first red bed unit is from an undisclosed location near the basin center; red mud from core cuttings was identified as Jurassic using palynology (Cross and Schafer 1968). Second, a variegated red-orange-purple-tan medium-grained, cross-bedded sandstone of unknown age, nicknamed the Ionia sandstone, was quarried in the southwestern central part of the basin and is present locally in building stones. We have identified a third red bed unit, composed of red and orange siltstones and fine-grained sandstones. These are found with coal in mine dumps along the eastern margins of the basin. A diverse assemblage of plant macrofossils characterize this third red bed unit and suggest a Mississippian - Permian age. The three units differ from each other in sedimentary textures, sedimentary structures, fossil assemblages, diagenetic features, and color. The red bed problem in Michigan can only be resolved with shallow coring throughout the Lower Peninsula of Michigan, followed by a detailed sedimentological, stratigraphic, and paleontological study of any red bed core samples.