Abstract

The variable mantle of glacial drift which covers the Michigan Basin prohibits the use of seismograph or magnetometer except in small local areas. The gravity meter, although influenced by the erratic drift, reveals maximum values over the Niagaran Reefs and has accounted for most of the reefs found to date. Gravity and structure maps of the Peters Reef in St. Clair County are presented to show the typical circular gravity maximum nearly coincident with the Salina A-1 structure.

A gravity profile across the Scipio Field suggests that the productive Trenton fracture zone is coincident with a basement fault. Similar fault patterns are associated with the Trenton production at Northville and Deerfield. Gravity surveys can map such faults and thereby indicate additional areas where similar Trenton fractures could be expected.