ABSTRACT: Roles of Algae in Development of Silurian Pinnacle Reefs, Michigan Basin Region: Evidence from a Pinnacle Reef at Maumee, Ohio

KAHLE, CHARLES F., Bowling Green State University, Bowling Green, OH

Understanding the development of Silurian pinnacle reefs in the Michigan basin region is critical to exploring for hydrocarbons in these reefs. The only exposure of such reefs in the region is at a quarry in Maumee, Ohio. The Maumee pinnacle reef is represented by 83 ft of the Lockport dolomite and 55 ft of an overlying unit termed the Maumee algal stromatolite by Gill (1985). The Lockport is a mosaic of patch reefs and interreef facies. Earliest reefs are deeper-water branching coral baffelstone reefs with mudstone matrix, and little evidence of algae. These reefs give way upward to diverse but coeval shallow-water patch reefs: algal stromatolite reefs, branching coral reefs, and Favosites (coral) reefs. Thrombolites and algal stromatolites were important sediment binders in the Favo ites reefs, and algal stromatolites also encrusted exposed portions of coral framestones. Algal stromatolite patch reefs, never before reported in any Silurian reefs in the Michigan basin region, served as substrates for most branching coral and Favosites reefs. The calcareous alga Renalcis grew downward from the roofs of cavities as well as upward on exposed portions of some Favosites reefs. Some Renalcis served as substrates for algal stromatolites. These findings suggest that algae were much more diverse in nature and played a much greater variety of roles in the development of Silurian pinnacle reefs in the Michigan basin region than has been realized previously. Caution should be used in assuming that algal stromatolites, thrombolites, coral reefs, and Renalcis indicate different wa er depths.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)