ABSTRACT: The Lower Mississippian Coldwater Shale andMarshall Sandstone span the Kinderhookian-Osagean (mid-Tournaisian) boundary in the Michigan Basin. Recent sequence stratigraphic analysis of these Lower Mississippian clastics reveal the Coldwater Shale and theMarshall Sandstone were deposited as parts of two different third order sequences (Vail sequences). More specifically, the Marshall Sandstone was deposited as a forced regressive deposit.Aforced regressive deposit is a basinward shift of the shoreline that is a direct result of sea level fall, and the sea level fall during the Lower Mississippian may have been driven by a glacial event in Gondwana. The Lower Mississippian clastic deposits of the Michigan Basin associated with this forced regression can also be identified in adjacent areas in North America. Forced regressive deposits contain a different suite of facies, lithologies, and spatial relationships than other types of regressive deposits. The spatial relationships, bounding surfaces, and internal characteristics that distinguish theMarshall Sandstone as an attached forced regressive deposit are discussed herein.