Galesville Sandstone

Munising Group,

Cambrian System

Type section: The Galesville Sandstone was named for an exposure of 88 feet (27 m) of sandstone overlying the Eau Claire Formation and underlying the Ironton Formation along Beaver Creek in Galesville, Trempealeau County, Wis. (Trowbridge and Atwater, 1934, p. 45).

Description: As traced to Indiana and described by Becker, Hreha, and Dawson (1978), the Galesville Sandstone in the subsurface of northwestern Indiana consists of fine- and coarse-grained sandstones conformably overlying the Eau Claire Formation and grading upward into the Ironton Sandstone. In part of this area the Galesville and Ironton Sandstones cannot be easily distinguished from one another. Both of these sandstones grade laterally into the Davis Formation and are nomenclaturally separated from the Davis by an arbitrary cutoff in central northern and western Indiana. These two formations are therefore recognized in Indiana only in the parts or all of 25 northwestern counties. The Galesville and the Ironton together range in thickness from about 100 feet (30 m) at the arbitrary cutoff with the Davis Formation to more than 200 feet (61 m) in the northwest corner of Indiana. In several counties in northwestern Indiana where the Galesville and the Ironton can be distinguished separately, the Galesville averages about 75 feet (23 m) in thickness.

Correlation: The Galesville Sandstone is also recognized by this one name in Illinois and Wisconsin, and it is equivalent to the lower part of the Davis Formation in central and southern Indiana and eastern Missouri, to the lower part of the Elvins Formation in western Kentucky, and to the lower part of the Potosi Dolomite in that part of southwestern Indiana where the Davis Formation has been replaced laterally by the Potosi (Droste and Patton, 1985).

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