The Frasnian/Famennian boundary in central and eastern United States

Abstract

The Frasnian/Famennian (F/F) Boundary in the northern Appalachian Basin is found in the Hanover Shale and equivalent strata where it is locally associated with a black shale interval equivalent to the Upper Kellwasser interval in Europe. The boundary is immediately below the Dunkirk–Huron black shale that represents the IIe T–R cycle transgression. In the southern Appalachian Basin, the southern edge of the Cincinnati Arch, and the southeastern Illinois Basin the F/F boundary is at or near the base of the Gassaway Member of the Chattanooga Shale or the Morgan Trail Member of the New Albany Shale, or was eroded during the IIe T–R cycle beginning in the Middle triangularis Zone. In the western Illinois Basin (Grassy Creek Shale), Michigan Basin (Lachine Member of Antrim Shale), and southern continental margin (Woodford Shale) the F/F boundary is within black shale strata, indicative of an earlier development of the IIe T–R transgression inboard of the Appalachian Basin or the juxtaposition of the IIe T–R transgression over the Upper Kellwasser black shale interval without significant or recognizable lithologic change.