Pennsylvanian System

Type section: The name Bridge Junction Sandstone Member was first used by Friedman (in preparation) in describing a sandstone exposed at Bridge Junction in Coal Creek valley in the NE¼ sec. 29, T. 13 N., R. 9 W., 3 : miles (6.0 km) southwest of New Goshen, Vigo County, Ind. The Bridge Junction exposure was designated the type section because it shows the thickest sandstone and typical bedding of the rock. Because the vertical stratigraphic relationships of the member are not clearly shown at the type section, Friedman designated a subsurface reference section in a drill hole 2 miles (3.2 km) south-southeast of New Goshen and 1 mile (1.6 km) west-northwest of Bridge Junction in the NE¼NE¼ sec. 30, T. 13 N., R. 9 W., Vigo County.

Description: The Bridge Junction is a light-brown sandstone that is massive, thick bedded to crossbedded, and fine grained to medium grained. The unit weathers red brown. The brown color of fresh samples of sandstone is typical of channel deposits. In places this sandstone is slightly calcareous. The sandstone averages 30 feet (9 m) in thickness however, it is as much as 90 feet (27 m) thick in sec. 26, T. 13 N., R. 9 W., Vigo County. It is overlain by a thin noncalcareous to calcareous gray shale, which is overlain by the Universal Limestone Member of the Dugger Formation. In the absence of both the shale and the limestone, the sandstone is overlain by underclay. The Bridge Junction Sandstone Member occupies channels or valleys eroded into sandy shale, interlaminated shale and sandstone, and thick gray shale of the Dugger Formation. It is present in the New Goshen Channel and its tributaries in Vigo County (Friedman, in preparation).

Correlation: Although he did not use the name Bridge Junction, Friedman (1960, p. 28) stated that the sandstone in the New Goshen Channel, which is now the Bridge Junction sandstone, was in the same stratigraphic position as a thick sandstone that lay below the Danville Coal Member of the Dugger Formation in Sullivan and Knox Counties. The New Goshen Channel sandstone was also equated with the Anvil Rock sandstone of Illinois and Kentucky by Friedman (1960). Anvil Rock-filled channels were mapped in southern Illinois, southwestern Indiana, and western Kentucky by Hopkins (1958), and in this compendium the name Anvil Rock Sandstone Member of the Dugger Formation has been formally introduced by Curtis H. Ault for use in Posey, Gibson, and Knox Counties in southwestern Indiana. Although the Anvil Rock and the Bridge Junction are at the same stratigraphic position, further study is needed to determine if they belong to one body of rock and to establish definitive correlation.