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ABSTRACT: Strata in Indiana between Ordovician rocks below and the Salamonie Dolomite above represent a single blanket deposit dominantly of carbonate lithology that is divisible into three major facies. Each facies is recognized as a formation. The long-established Brassfield Limestone is restricted to an area south of Grant County and the northern parts of Delaware and Randolph Counties and east of the western margins of the Madison Trend (new) and Ripley Island. The Cataract Formation, introduced into Indiana usage here, is north of the area of recognition of the Brassfield Limestone and east of the Madison Trend. The rest of the state is underlain by the Sexton Creek Limestone, an extension of the use of the name from the Illinois Basin into northern Indiana. The Cataract consists in ascending order of the Manitoulin Dolomite Member and the Cabot Head Member, both newly introduced into Indiana usage, and the Stroh Member, a new name. In Indiana the Manitoulin and the Cabot Head together are equivalent to the Brassfield and the Sexton Creek of Indiana and the Cataract Group of Michigan as these already established terms have been used in those states. The Stroh is laterally equivalent to the lower part of the Salamonie Dolomite as the Salamonie is now defined outside the area of Cataract recognition; that is, the Salamonie lies above the Brassfield, the Cataract, or the Sexton Creek in their respective areas and underlies the Limberlost Dolomite, the Waldron Shale, or the Salina Formation, whichever is the lowest formation present.



Rexroad, C. B. 1980, Stratigraphy and conodont paleontology of the Cataract Formation and the Salamonie Dolomite (Silurian) in northeastern Indiana: Indiana Geological Survey Bulletin 58, 83 p., 5 fig., 1 pl.


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Keywords: stratigraphy, conodont, paleontology, Silurian, Cataract Formation, Salamonie Dolomite, Cabot Head Member Member, Stroh Member, fossil, Brassfield Limestone, Sexton Creek Limestone, Manitoulin Dolomite Member

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