Date of Award

12-1981

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. William B. Harrison III

Second Advisor

Dr. John D. Grace

Third Advisor

Dr. W. Thomas Straw

Access Setting

Masters Thesis-Open Access

Abstract

The Rockport Quarry Limestone of the Lower Traverse Group represents a sequence of laterally contemporaneous carbonate platform sediments characterized in outcrop by four facies: (l) stromatoporoid biolithite, (2) organic-mud packstone, (3) biolithite-micrite transition, and (4) micrite. In facies (l), (2) and (3) dark brown 4-micron microspheres are found grouped or singly in wispy seams of brown carbonaceous material. Three species of filamentous blue-green algae were discovered in insoluble residues of facies (l) and (2). Numerous lamellar stromatoporoids and solitary corals occur with the carbonaceous-rich sediment in facies (l). Coalescing lenses of crinoid and bryozoan debris occur with the carbonaceous sediment in facies (2). Algal-laminated sediments* calcareous red algae, and calcareous blue-green algae are present in facies (4), as well as two new foraminifers in facies (l) and (3). The size range and morphology of the non-nueleated microspheres suggest that they are coccoid blue-green algae. The kerogenous material composing the seams probably represents fossilized sheath material secreted by the algae. The carbonaceous seams, microspheres, and algal filaments are interpreted as subtidal algal mats that provided a firm substrate upon which stromatoporoids could grow.

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