Sexton Creek Limestone, Type section and use of name: The
Schweizer Member of the Wilhelmi Formation was named by Willman
(1973) for Schweizer School 1 mile (1.6 km) west of the type
section, which is part of the Wilhelmi type section, in the SE¼
sec. 35, T.35 N., R.9 E., Will County, Ill. The lithologic
distinctions between the Birds Member of the Wilhelmi and the
overlying Elwood Formation of Illinois are lost in northwestern
Indiana, and the lithologic equivalents of each are included in
the Sexton Creek Limestone. Because the lower member of the
Wilhelmi, the Schweizer, is both laterally and vertically
gradational with the Sexton Creek in Indiana, it is included as
a member of the formation in Indiana (Rexroad and Droste, 1982).
Description: The Schweizer Member generally consists of
intermixed dolomitic shale and shaly to argillaceous dolomite.
Silty intervals and patches of siliceous dolomite are present in
some areas, but the unit has little or no chert. Reworked
Ordovician material, including fossils,