Whitewater Formation


Maquoketa Group,

Ordovician System

Type Locality, description, and correlation: The Whitewater Formation was named by Nickles (1903, p. 208) for exposures of bluish-gray rubbly limestone and interbedded calcareous shale along the Whitewater River at Richmond, Wayne County, Ind. As now recognized, the Whitewater includes at its

base a dolomitic unit, the Saluda Member (Gray, 1972b), and in its uppermost part shale and limestone formerly placed in the Elkhorn Formation (Utgaard and Perry, 1964). The Whitewater Formation contains a somewhat higher proportion of limestone than does the underlying Dillsboro Formation, but this alone is not distinctive it is the Saluda Member at its base that best distinguishes the Whitewater.

The Whitewater Formation conformably overlies the Dillsboro Formation (except as noted below) and is disconformably overlain by the Brassfield Limestone (Silurian) except in a few places in Clark, Jefferson, Ripley, and Decatur Counties, where the Brassfield is absent and the Osgood Member of the Salamonie Dolomite directly overlies the formation (Foerste, 1891, 1904a; Brown and Lineback, 1966, p. 1022; Nicoll and Rexroad, 1968). The disconformable nature of this contact is emphasized by reworked Ordovician fossils in the basal part of the Brassfield Limestone.

Traditionally, the Whitewater Formation is recognized in Indiana only in the classic Cincinnatian outcrop area in the southeastern part of the state and in the near subsurface. Within this area the formation thins southward from about 100 feet (30 m) near Richmond to about 60 feet (18 m) near Madison, where the formation is reduced to its basal Saluda Member. At the top of the Maquoketa Group in northeastern Indiana, however, Gray (1972b, p. 18-20 and fig. 13) identified an informal working unit as much as 160 feet (50 m) thick that is stratigraphically equivalent to the Whitewater and that, because it is dominantly limestone, is here assigned to the Whitewater Formation rather than to the laterally equivalent Brainard Shale. Thus extended, the Whitewater of northeastern Indiana rests, probably conformably, on the Fort Atkinson Limestone.

Near the top of the Whitewater in northeastern Indiana, especially in areas where the formation is thickest, are zones containing ferruginous reddish-brown ooids, beds of sedimentary iron ore, and limestone with hematitic cement. These have not been observed elsewhere in the Maquoketa in Indiana, but similar materials are found in the presumably correlative Neda Formation, which is at the top of the Maquoketa Group in northern Illinois (Kolata and Graese, 1983, p. 29). The Whitewater is the uppermost formation in the type Richmondian Stage, but its subsurface extension, where thickest, probably includes Ordovician rocks that are somewhat younger than any that are exposed in the Richmond area (Gray, 1972b, p. 19-20).

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