Leopold Limestone Member


Branchville Formation,

Mississippian System

Type section and description: The Leopold Limestone Member was named by Gray (1978, p. 10) for exposures near Leopold in central Perry County. The type section is in a road cut on former State Route 37 and was initially described by Malott, Esarey, and Bieberman (1948, p. 13). In this section the Leopold Limestone Member is 12 feet (4 m) thick and consists of three beds of limestone separated by shale. This section was also reported by Rexroad and Nicoll (1965, p. 15). Indiana Geological Survey drill hole 132 (Gray, 1978, appendix 2) near Oriole in Perry County is here designated as a reference section. In this drill hole the Leopold member is 11 feet (3 m) of micritic dolomite in two beds separated by 1 foot (0.3 m) of shale.

According to Gray (1978, p. 10), the Leopold Limestone Member is "the most continuous member in the outcropping upper Chesterian of Indiana," and for this reason it was selected to mark the top of the Branchville Formation. As presently understood, the member is 4 to 12 feet (1 to 4 m) thick, but isolated exposures of limestone as much as 20 feet (6 m) thick in eastern Dubois County, once assigned to the Siberia Limestone Member, are now considered likely to belong to the Leopold.

Commonly the Leopold consists of white to gray limestone and dolomite that weather light yellow brown and that form a double ledge with a shale break. The member extends from the Ohio River northward to southwestern Orange County, where it has been seen in a hilltop excavation just south of the Patoka Reservoir. At that point it directly overlies a sandstone ledge that was assigned by Malott (1925) to his Wickliffe Sandstone in most places, however, the Leopold conformably overlies shale of the upper part of the Branchville Formation. It is overlain conformably by the Tobinsport Formation and is truncated northward by the disconformable base of the Mansfield Formation (Morrowan).

Correlation: The Leopold Limestone Member is a tongue of the Menard Limestone. If the "Chapman sand" of the Owensboro, Ky., area (Swann, 1963, p. 38) is equivalent to Malott's (1925) Wickliffe Sandstone, as seems likely, then the Leopold probably represents the basal part of the Scottsburg Limestone Member, the middle of three limestone members that are separated and overlain by three unnamed shale members and that make up the Menard Limestone of the standard Chesterian section (Swann, 1963, p. 38-39; Willman and others, 1975, p. 160).

The Leopold Limestone Member correlates with rocks within North American foraminiferal Zone 17 of Mamet and Skipp (1971) and with rocks of the Namurian Series near the boundary between Zones El and E2 of European usage. Conodonts representative of the Kladognathus-Cavusgnathus naviculus Assemblage Zone of the standard North American zonal scheme were reported by Rexroad and Nicoll (1965) from collecting sites now assigned to the Leopold Limestone Member.

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