Date of Award


Degree Name

Master of Science


Geological and Environmental Sciences

First Advisor

Dr. William B. Harrison III

Second Advisor

Dr. W. Thomas Straw

Third Advisor

Dr. Raymond Freeman-Lynde

Access Setting

Masters Thesis-Open Access


The lower Salina Group of the Michigan Basin is composed of a cyclic succession of carbonate and evaporite units. The lowermost Salina unit is the A-1 unit which consists of a lower A-1 evaporite and an upper A-1 carbonate. The A-1 unit is underlain by Niagara Group carbonates. The transition from Niagaran carbonates to A-1 evaporite to A-1 carbonate has not been thoroughly understood and previous models have not satisfied some of the evidence. This paper sets forth the hypothesis that the A-1 carbonate was deposited in a non-marine lake environment rather than an isolated marine environment. Findings supporting this include: 1) Basin morphology; 2) lack of marine organisms; 3) evaporite-free carbonate laminae; 4) dessication breccias suggestive of drying and refilling ; and 5) nodular anhydrite around pinnacle reefs indicative of a sabkha-type environment and therefore exposure of the basin margins causing isolation of the basin from marine waters.

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