Michigan Geology

A geologist would describe the Michigan geological basin as the bowl-shaped remains of an ancient tropical sea. The ancient sea bed is layered with millions of years of younger sedimentary rock. This bowl-shaped assemblage of rock and soils extends east beyond Niagara Falls, west beyond Prairie du Chien, Wisconsin, north to the edge of Michigan's Upper Peninsula where it meets with the volcanic rock of the Lake Superior Basin and south to just beyond the Michigan-Ohio border. Strata of rock within the basin are labeled by their geological age and geological formations layered within the geological age groups.

Formations in a geological basin are also often referred to by the location where they "outcrop," that is reach the earth's surface. In the Michigan Basin, some formation names, like the Detroit River formation, are obvious. Others are more obscure. The Salina Niagaran formation is named for the Niagara River and the deep Prairie du Chien for Prairie du Chien, Wisconsin.

The rock under the earth varies in density. Some of the layers are quite porous, allowing liquids or gases to move through them, while others are quite dense, forming natural barriers to the movement of liquids or gases. Within the more porous layers are deposits of oil and natural gas, called reservoirs, often accompanied by salt, brine, or fresh water. These reservoirs are contained by denser, nonporous rock.

The mitten of the Lower Peninsula of Michigan sits almost in the center of this bowl-shaped basin, with the deepest part believed to be in the neighborhood of St. Louis and Alma (St. Louis being exactly in the center of the Lower Peninsula). There drillers must sink well bores more than 17,000 feet to reach the volcanic rock of the Lake Superior Basin which you can get out of your car and look up at in the Upper Peninsula.

The lack of sedimentary rock in the Upper Peninsula makes it unlikely that oil and natural gas in commercial quantities exist there. Despite the odds, fourteen holes have been drilled in the "U.P." but none has been found in commercial quantities.

That's the geologist's version. For lay folk, here is another way to picture Michigan's geology. Imagine a bowl of raisin bran, with the raisins representing the porous rock containing oil and natural gas. Some of the raisins are bigger while some are smaller. The bran symbolizes the denser rock that keeps the oil and natural gas within the raisins. There is a lot more bran than raisins. Now, imagine several such bowls of raisin bran, each bowl a little smaller than the one underneath it, stacked together one inside the other like your mixing bowls at home. Picture the whole group of bowls scraped and layered by glacial deposits then covered with a mitten-shaped piece of graph paper. Finally, take a jeweler's drill and try to hit a raisin. A petroleum landman, hearing this analogy, once quipped "And in Michigan we're blessed with two scoops of raisins!"

For more than fourteen decades, oilfolk have looked for the raisins in the Michigan Geological Basin in a quest to find, originally, lighting fuel and later, transportation fuel.