The Roles of Far Field Stress and Mantle Downwelling In Intraplate Deformation: The Michigan Basin

The Michigan basin has long been established as the type example of an intracratonic basin due to its near circular geometry and gently inward-dipping Paleozoic formations. The backstripping of major formations within the basin reveals that its geometry varied over the duration of the Paleozoic, displaying two distinct subsidence signals consisting of quasi-circular basin-centered subsidence interspaced with periods of irregular basin geometry. The quasi-circular basin-centred subsidence is thought to represent the surface expression of a driving mechanism located beneath the Michigan basin, which persisted for the duration of the Paleozoic. An irregular subsidence geometry periodically interrupts the quasi - circular basin-centred pattern and is contemporaneous with the Ordovician Taconic and Devonian Acadian orogenies. Through the use of scaled analogue experiments, the effects of convective mantle downwelling and long wavelength folding are explored as potential driving mechanisms to explain the subsidence patterns of the Michigan basin. Convective mantle downwelling is hypothesized as the process responsible for the quasi-circular basin-centered subsidence patterns and the relationship between mantle flow velocities and a variety of continental strength profiles is explored. A series of scaled analogue vice experiments explore the effects of regional orogeny on a continental hinterland, with some experiments containing a strong lower crustal strength heterogeneity, designed to test the possible influence of the Mid Continental rift beneath the Michigan basin. The results of both types of experiment demonstrate that quasi-circular subsidence patterns within the Michigan basin may have been formed due to convective mantle downwelling, while the effects of regional orogeny and long wavelength folding dramatically influenced subsidence patterns during the Taconic and Acadian orogenies.Ph