--> Abstract: Precambrian Geophysical Provinces in Indiana, by Albert J. Rudman, Judson Mead, Robert F. Blakely, Joseph F. Whaley; #90975 (1976).
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Abstract: Precambrian Geophysical Provinces in Indiana

Albert J. Rudman, Judson Mead, Previous HitRobertTop F. Blakely, Joseph F. Whaley

Regional statewide gravity and magnetic surveys in Indiana reveal large areas of high and low intensities. The source of these variations is lithologic changes within the Precambrian basement. A generalized map of basement provinces, constructed from both gravity and magnetic data, identified regions of basement lithologies as either dense or magnetic-rich rocks or combinations thereof.

Analyses of intense, magnetic anomalies reveal the basement surface to range from 2,000 to 11,000 ft (610 to 3,353 m) below sea level. Many of the anomalies appear to be concentrated along the Cincinnati arch. Detailed studies of two regions suggest that the sources may be basaltic pipe-like intrusions into a granitic country rock. Lava-flow structures may be associated with the individual pipes.

AAPG Search and Discovery Article #90975©1976 GCAGS- GC Section SEPM Annual Meeting Shreveport, Louisiana