ABSTRACT: Facies Changes in the Early Silurian, Manitoulin and Cabot Head Formations in the Michigan Basin.

BAILEY, D. J., T. R. MANESS, and D. J. MANESS, Maness Petroleum Corporation, Mt. Pleasant, MI

Several hundred deep tests recently drilled in the center of the Michigan basin provide the data base to map complex facies changes in the early Silurian, Alexandrian sequence.

The lowermost Manitoulin Carbonate was deposited on a significant unconformity at the top of the Late Ordovician, Cincinnatian Series. Variations in the paleotopography dramatically influence the distribution and thickness of the Manitoulin Formation. Bioconstruction appears to have flourished around the margins of the basin with a substantial carbonate bank being built in the south-central portion of the basin. The margins of the bank may have provided an environment for reefing similar to that seen in the Late Niagaran around the margins of the basin.

The overlying Cabot Head Formation contains mainly shales around the margins of the basin. The shales change facies to an evaporite sequence in the center basin area. The distribution of the various facies of the little studied Alexandrian section appears to be a precursor to the prolific Niagaran age bioconstruction that has produced significant hydrocarbons in the basin.

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)