Source Rock Potential of Nonesuch Shale, White Pine District, Michigan

David A. McMahon, William A. Kneller

The White Pine mining district at the western end of Michigan's Upper Peninsula has long been known to contain Precambrian hydrocarbons. Here the Nonesuch Shale is the source rock. This 1-b.y.-old Keweenawan shale sequence possesses several key characteristics that make it a good source rock. The shale has 0.8-1.2 wt. % organic carbon and an alkane diversity of greater than 600 µg/g shale, as extractable bitumen. These extractable hydrocarbons consist of less than 2 µg/g shale gasoline-range hydrocarbons but a significant amount of plus C₁₀₊ hydrocarbons, including pristane, phytane, and measurable vanadyl-porphyrins. These hydrocarbons place the Nonesuch Shale in the good source rock range as defined by total hydrocarbon content and diversity. Additi nally, a mild thermal history is essential for a formation of this age to have sufficient maturity to retain economic amounts of hydrocarbons. This maturity is implied by the presence of thermally sensitive vanadyl-porphyrins.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.