The Michigan structural basin is symmetrically centered in the Southern Peninsula of Michigan and extends outward into surrounding states and the Province of Ontario. Outcrops of Precambrian rocks bound the basin to the north; on the east the Algonquin axis in Ontario is the basin border, and to the south and west, the limiting features are the Findlay and Kankakee arches of northern Ohio and Indiana and the Wisconsin arch in central Wisconsin. Paleozoic rocks crop out, or underlie the glacial drift, in circular bands with the youngest rocks occurring near the center of the Southern Peninsula where the floor of the Paleozoic rocks in the basin reaches its maximum depth of about 14,000 feet.

Oil production in the Michigan basin had its beginning at Petrolia in Ontario in 1858, but production in volume began with the discovery of the Muskegon field on the west side of the basin and the Mount Pleasant field near the center of the basin in 1928. Approximately 270 oil fields and more than 100 gas fields have been discovered in the basin.

The Michigan basin contains about 108,000 cubic miles of sedimentary rocks of which about 80 per cent is Cambrian, Ordovician, and Silurian in age, and most of the remainder Devonian in age. Lithologically, carbonate rocks constitute 47 per cent of the sedimentary rocks of the basin, 12 per cent being evaporites, and the remaining 41 per cent sandstones and shales.

More than 95 per cent of the oil has come from carbonate rocks of Middle Devonian age, and most of the gas is from sandstones of Mississippian age. The oil yield to date amounts to 3,700 barrels per cubic mile of sedimentary rock.

The producing formations, from oldest to youngest, are the Black River and Trenton limestones of Middle Ordovician age, the upper part of the dolomite of the Niagara Series of Middle Silurian age, and dolomite in the lower part of the Salina formation of Late Silurian age, various limestones and dolomites of Middle and Late Devonian age including the Detroit River group, the Dundee and Rogers City limestones, and Norfolk formation of Canada, the Traverse group, and sandstones of Mississippian age. Accumulation of oil is largely anticlinal, with northwest-southeast trends predominating in the central basin area. Most of the folding took place during late Paleozoic time. The greater part of the oil has been produced from porous zones below unconformities. This is due mainly to the devel pment of secondary porosity at the top of the limestones, but some accumulations beneath unconformities are in porous zones due to secondary dolomitization.