Chesterian Series

Mississippian System

Type locality and history of name in Indiana: The Buffalo Wallow Formation was named by Butts (1917, p. 112-117), who included in it ail Chesterian rocks above the Tar Springs Sandstone. In a modified sense, the term has had extensive use in mapping in Kentucky (for example, Amos, 1970; Bergendahl, 1965; Clark and Crittenden, 1965; Crittenden and Hose, 1965). The formation is primarily shale, mudstone, and siltstone, but it also includes thin beds of limestone and sandstone. At the type locality near Cloverport, Ky., on the Ohio River, the formation is 265 feet f 80 m) thick (Malott, 1925, p. 116).

About 60 years ago the name Buffalo Wallow Formation was also applied in Indiana (Malott and Thompson, 1920: Cumings, 1922, p. 518). The term was not, however, adopted by Malott (1925) in his seminal study of upper Chesterian rocks. He was concerned with subdividing the upper Chesterian and apparently did not perceive a need for a group term. At group rank and in a somewhat expanded sense, the name was adopted by Gray (1978) to include ail outcropping Mississippian rocks above the Glen Dean Limestone. This usage differs from that in Kentucky in rank assignment and by including the Tar Springs Formation in the group, but it "expresses well the lithologic unity of the upper Chesterian and it retains an old and established name" (Gray, 1978, p. 5).

As originally defined for Indiana usage, the term Buffalo Wallow Group was not extended into the subsurface (Gray, 1978), but it is now finding application there in a substantially identical sense--that is, to include all Mississippian rocks above the Glen Dean Limestone. In surface usage the three formations of the group in ascending order are the Tar Springs, Branchville, and Tobinsport Formations. In the subsurface the component formations are the Tar Springs Formation, the Vienna Limestone, the Waltersburg Sandstone, the Menard Limestone, the Palestine Sandstone, the Clore Limestone, the Degonia Sandstone, the Kinkaid Limestone, and the Grove Church Shale.

Description: The Buffalo Wallow Group is dominantly shale, mudstone, and siltstone, but it also contains prominent beds of sandstone and limestone, some of which are laterally extensive. The group exhibits its maximum surface thickness of about 270 feet (82 m) near Tobinsport on the Ohio River in the subsurface its maximum thickness is about 750 feet (200 m) in Posey County. It thins progressively and is truncated northward as a result of pre-Pennsylvanian erosion, so that in the subsurface its northern margin crosses southwestern Sullivan County, Daviess County, and northeastern Dubois County. Along the outcrop it reaches no farther north than southwestern Orange County.

Correlation: Rocks now assigned to the Buffalo Wallow Group were found by Collinson, Rexroad, and Thompson (1971) to span three conodont zones of North American standard usage: in descending order they are the Kladognathus-Cavusgnathus naviculus Assemblage Zone, the KIadognathus primus Assemblage Zone, and the upper part of the Gnathodus bilineatus-Kladognathus mehli Assemblage Zone. The group equates with rocks within North American foraminiferal Zones 17 and 18 of Mamet and Skipp (1971) and with part of the Namurian Series (Zones E1 and E2) of European usage.