English: Weathered shales unconformably overlying dolostone in the Devonian of Kentucky, USA.

The upper part of this overgrown roadcut consists of weathered dark shales of the Portwood Member, an offshore marine succession at the base of the New Albany Shale / Ohio Shale. The lower Portwood has linguloid and orbiculoid brachiopods and Zoophycos trace fossils. Intervals with deformed bedding interpreted as seismites are present in the lower Portwood. The base of the middle Portwood is an unconformity. The basal bed of the middle Portwood is a dolostone with a burrowed lower surface. Brachiopods identical to forms in the Tully Limestone of New York State occur in the middle Portwood.

The lower part of the cut consists of carbonates (less than 1 meter thick) that are the lateral equivalent of the Beechwood Member of the North Vernon Limestone (= Middle Devonian crinoidal limestones). At this site, the equivalent beds are called the Boyle Dolomite or Boyle Formation.

Stratigraphy: Portwood Member of the basal New Albany Shale / Ohio Shale (middle Polygnathus varcus zone, Givetian Stage, upper Middle Devonian) over the Beechwood Member of the Boyle Dolomite / Boyle Formation (lower Polygnathus varcus zone, Givetian Stage, upper Middle Devonian)

Locality: Waco Cut - roadcut along the northern side of Route 52, ~0.2 miles east of the Route 52-Route 977 intersection at the town of Waco, eastern Madison County, east-central Kentucky, USA (37˚ 44.471’ North latitude, 84˚ 08.566’ West longitude)

---

Info. at:

Schieber, J. & R. Lazar (eds.). 2004. Devonian black shales of the eastern U.S. New insights into sedimentology and stratigraphy from the subsurface and outcrops in the Illinois and Appalachian Basins. Field Guide for the 2004 Annual Field Conference of the Great Lakes Section of SEPM. Indiana Geological Survey Open-File Study 04-05. 90 pp.