Mississippian System

Type locality and use of name: The name New Providence Shale was used by Borden (1874) for 80 to 100 feet (24 to 30 m) of shale "at the base of the knobs and immediately above the ferruginous [Rockford] limestone." He did not designate a type section, but he included rocks up to the "true knob shale," which is interpreted to be the Spickert Knob Formation of present use. The formation was named for New Providence, Floyd County, Ind., but typical exposures "are not seen nearer than about four miles east of the town" (Stockdale, 1961, p. 85). Exposures are to be found in the lowlands and lowest part of the Knobstone Escarpment both north and south of Broomhill, which is in the southwest corner of sec. 5, T. 1 S., R. 6 E. One of the best natural exposures of the New Providence is on the south end of Kenwood Hill in the southern part of Louisville, Jefferson County, Ky. This is the type section of the Kenwood Member of the New Providence Shale. (See "Borden Group" for a discussion of obsolete terms that have been applied to the New Providence interval.)

Description: Greenish-gray, blue-gray, or dark-lead-gray shale bordering on claystone is the dominant lithology of the New Providence, although the Kenwood Member is a clayey, poorly sorted fine siltstone interbedded with shale similar to the rest of the New Providence. Ironstone lenses or beds generally less than 1 foot (0.3 m) thick and composed mainly of iron carbonate are irregularly distributed throughout most of the formation in southern Indiana. Both fossiliferous and unfossiliferous limestones are present as concretionary bands, beds, or biohermlike patches, but these are more common in Kentucky than in southern Indiana. Minor amounts of red shale are present, most commonly in the northern half of the outcrop area of the formation. To the north beds of siliceous silty dolomite several feet thick are present in places.

In Indiana the Kenwood Member is essentially limited to Floyd County, where its maximum thickness is slightly more than 50 feet (15 m). On outcrop the rest of the New Providence ranges from about 150 to 250 feet (46 to 76 m) in thickness. The Kenwood wedges out to the west within the New Providence, and as a prodelta deposit, the New Providence as a whole thins and loses its identify within the Borden to the southwest.

The Rockford-New Providence contact is sharp, although the two apparently are conformable in northern Indiana. The contact is erosional in southern Indiana, and where the Rockford Limestone is absent the New Providence rests on the New Albany Shale. The boundary of the New Providence with the overlying Spickert Knob Formation is gradational and in part intertonguing, and therefore a contact is difficult to pick in many areas but is recognized on the basis of the upward change from a dominantly clay shale to a very silty shale.

Correlation: Conodont studies (Rexroad and Scott, 1964) showed that the New Providence Shale is time transgressive and is oldest in its northern outcrop area where the lower part is equivalent to the lower part of the Burlington Limestone or the Fern Glen Formation of the Mississippi Valley and is a part of the Bactrognathus-Polygnathus communis Assemblage Zone. To the south the basal part of the New Providence is younger and correlates with part of the Keokuk of Iowa (Butts, 1915; Kammer, Ausich, and Lane, 1983; Kammer, 1984). The upper limit of the correlation is indefinite but is within the Keokuk. Nowhere is the New Providence known to be of Kinderhookian age.