Structure, Stratigraphy, and Petroleum Geology of the Michigan Basin: Chapter 30: Part II. Selected Analog Interior Cratonic Basins: Analog Basin
The Michigan basin is in the upper midwestern part of the United States. The thickest part of this almost circular basin contains a lens of about 16,000 ft (4800 m) that consists mostly of marine sedimentary rock, ranging in age from Cambrian to Pennsylvanian. A small patch of terrestrial Jurassic rocks is also present in the central basin. Most of the sedimentary section is overlain by glacial deposits. Precambrian sedimentary rocks are preserved in the subsurface in an ancient rift zone that can be defined by geophysical techniques. Although the exact origin of the basin is still in question, an embryonic form was present by Late Cambrian time, and the basin attained its modern configuration during Ordovician time. The main structural grain of the basin is oriented northwest-southeast, and a complementary northeast-southwest trend also exists. In 1886 oil and gas were discovered in the Port Huron field in the Michigan basin; the modern era of oil and gas exploration in the basin began in 1925 with the discovery of the Saginaw field. Oil and gas have been found throughout the Paleozoic section except in Pennsylvanian- and Cambrian-age rocks, which have not yet yielded economically significant quantities of hydrocarbons. Exploitation of the basin's reserves has been a gradual process, developing from shallower to deeper horizons. At present, however, one of the shallowest formations (Antrim Shale) and one of the deepest (St. Peter Sandstone) are both the focus of intense exploration and exploitation.