The "Red Beds" of Michigan are comprised of red and greenish-gray shales and sandstones, and extensive lenses of gypsum, in the central part of the Michigan Basin. They unconformably overlie richly fossiliferous Pennsylvanian strata on a surface of low relief and are entirely unconformably overlain by up to 200 m of Quaternary glacial deposits. The "Red Beds" have been identified by a diverse palynoflora as mid-Jurassic in age (Bajocian-Bathonian). The sediments probably accumulated in the vicinity of a large inland playa or possibly a lake with internal drainage on a structurally controlled, reactivated, shallow depression. However, a possible alternative origin is the transgression of an epeiric sea through a restricted channel from the west or northwest for a limited time and the development of a sabkha-like environment on a broad coastal plain of very low relief. Absence of acritarchs/dinoflagellates indicates a non-marine origin. The palynoflora of the Michigan "Red Beds" is closely similar to that of the "Mistuskwia Beds" encountered in two bore holes in the Moose River Basin of the James Bay Lowland, Ontario. The "Mistuskwia Beds" were identified by G. Norris as mid-Jurassic in age. Species of Classopollis and bisaccate conifers dominate the palynoflora. Cycadeoids and up to four species of Eucommiidites are present in small numbers in most samples. Several pteridophytes and limited pteridosperms are generally present. Alisporites, Callialasporites, Cerebropollenites, Classopollis, Ginkgoretectina, Leptolepidites, Podocarpidites, Spheripollenites, and Vitreisporites sp. are the most important stratigraphic indicators. This palynoflora is compared with several palynofloras from the Jurassic rocks of southeast Saskatchewan, including the Gravelbourg, Shawnavon, and Sawtooth Formations, and with several Jurassic sections in the United States.

Key words: Jurassic, Michigan Basin, palynofloras, Red Beds