BIOSTRATIGRAPHIC CORRELATION OF THE MIDDLE DEVONIAN MAHANTANGO FORMATION, NORTHEASTERN WEST VIRGINIA AND SOUTH-CENTRAL PENNSYLVANIA

New exposures of a partially complete outcrop of the Middle Devonian Mahantango Formation (Hamilton Group) in south-central Pennsylvania, (at Chaneysville, Bedford County) were biostratigraphically zoned to complete a previous zonation of the lower part of the section. The Mahantango is a sequence of marine siltstone and shale, deposited in the Appalachian foreland basin during the Acadian orogeny. A previously established Mucrospirifer mucronatus zone was extended up 95 m into an unnamed shale. At the top of the section, a barren zone corresponds with the Clearville siltstone. The completed zonation was compared with a previously zoned outcrop in northeastern West Virginia (at Wardensville, Hardy County, about 75 km to the south). Only a partial correlation was possible. In the lower half of the section, a Longispina mucronatus/M. mucronatus zone and the overlying M. mucronatus zone at Chaneysville correlated with a M. mucronatus zone at Wardensville. Near the middle of the section, a zone of maximum species diversity was noted in both exposures in an unnamed siltstone member. Above that, no correlation could be made. Notably, a prominent rugose coralline zone present at Wardensville, near the top of the section in the Clearville siltstone, was absent at Chaneysville. In fact, corals were present throughout the section at Wardensville, while none were found at Chaneysville. Both exposures were barren at the top, however, this barren zone extended significantly lower in the section at Chaneysville and encompassed the entire Clearville siltstone. In general, both exposures show paleontological (based on diversity and body size of the fauna) and sedimentological (based on percentage of coarser lithologies) evidence for shallowing over time. The absence of corals at Chaneysville suggests greater water depth at that locality.