Date of Award


Degree Name

Master of Science


Geological and Environmental Sciences

First Advisor

Dr. William A. Sauck

Second Advisor

Dr. W. Thomas Straw

Third Advisor

Dr. John D. Grace

Access Setting

Masters Thesis-Open Access


A circular pattern to the oil production in Calvin Township, Cass County, Michigan, absence of about 1200 feet of Ordovician sediments and uplift indicated by a deep drill hole in the center of the productive area and absence of anomalies on the regional gravity and magnetic maps led to detailed gravity and magnetic surveys over this structure to delineate it and provide information regarding its genesis.

The Bouguer gravity and magnetic anomaly maps show no anomaly associated with the structure. The 28-mile wavelength second harmonic residual gravity and magnetic maps show linear features in the area. Two dimensional gravity modeling of the NNW-SSE trending linear feature over the area of circular production is interpreted as upthrusting involving the basement rocks. The NNW-SSE trending Jefferson field appears to be truncated by NE-SW trending faults.

The lack of a circular gravity anomaly and the lack of direct geologic evidence in support of the impact origin leaves the question of genesis open.