Spatial variations in tectonic subsidence during Tippecanoe I in the Michigan Basin

Abstract

AbstractEpisodic tectonic subsidence can be seen from all backstripped wells from the Michigan Basin. These episodes are observed as periods of relatively rapid subsidence, contrasting with the relatively linear subsidence. Steady tectonic subsidence curves have been explained as being due to a decaying thermal anomaly in the underlying uplifted asthenosphere. Rapid episodes of subsidence require another explanation and prompt us to examine the tectonic history of surrounding areas for correlative events.The Taconic orogeny has been inferred to have influenced the development of the Michigian Basin. To analyse the extent of coupling between the Appalachian foredeep and the Michigan Basin we have used Ordovician formation tops correlated among 172 wells distributed over the whole of Michigan's Lower Peninsula. The spatial variation of tectonic subsidence over this interval supports this suggestion.Contour maps of decompacted sediment thickness and subsidence rate show substantial changes in form and magnitude during the development of the Tippecanoe I sequence. Early basin‐centred subsidence, during deposition of the Shakopee, St. Peter and Glenwood formations, was followed by tilting toward the Appalachian orogen concurrent with the early stages of the Taconic orogeny. This tilting continued, declining gradually, during deposition of the Black River, Trenton and Utica formations. Deposition during Tippecanoe I in the Michigan Basin may indicate modulation of continuing thermally driven subsidence by flexure of the lithosphere due to Taconic thrust loading, but the distinctive spatial distribution of subsidence over each interval may indicate that the important mechanisms making space available in the basin operated independently, not concurrently, invalidating the flexural model for the coupling and suggesting other regional, tectonic possibilities for models of basin initiation, evolution and filling.