Silurian System

Type section, description, and use of name: The Red Bridge was named by Cumings and Shrock (1927, p. 74) as a formation and was later (Cumings and Shrock, 1928a, p. 72) regarded as a member for 1 to 6 feet (0.3 to 1.8 m) of light-colored fine-grained glauconitic dolomitic limestone that commonly weathers reddish brown and appears as a single bed on outcrop. The type section is at Red Bridge in the bluff of the Mississinewa River, Wabash County, Ind. (south-central part of Reserve 26, T. 26 N., R. 6 E.). The type section is now under water in the Mississinewa Reservoir during at least part of the year, as is the former exposure of this bed within the Liston Creek type section (Shaver and others, 1961, fig. 5), but good exposures remain along the Wabash River in western Wabash County. One of these is in the Indiana 13 and 15 road cuts in the south bluff south of Wabash (north-central part of sec. 18, T. 27 N., R. 6 E.), where the 1.4-foot (0.4 m) Red Bridge, basalmost Liston Creek, immediately overlies a 48-foot (15 m) section of the Mississinewa Shale Member (Wabash Formation). (See Pinsak and Shaver, 1964, p. 82.) Another good section flanks the Shanty Falls Reef, south bluff of the river valley, 1 mile west of Wabash (N2 Reserve 55, T. 27 N., R. 6 E.) (See Cumings and Shrock, 1928a, p. 76 and 151.)

The Red Bridge was reduced to the status Red Bridge Limestone Bed (Liston Creek Limestone Member) by Pinsak and Shaver (1964, p. 39). The name has had little or no use outside Wabash County, although glauconite is found elsewhere in the lower Liston Creek rocks, for example, in Howard County (Shaver and others, 1961, p. 13).