The upper part of this roadcut consists of fine-grained siliciclastics of the Portwood Member, an offshore marine succession at the base of the New Albany Shale / Ohio Shale. The lower part of the cut consists of carbonates of the Boyle Formation.
The contact is an unconformity - a surface of erosion and/or non-deposition of sediments. The orangish-brown stains on the Boyle are iron oxides derived from weathering of pyrite at or near the unconformity. These are called "bleeding unconformities".
Stratigraphy: Portwood Member of the basal New Albany Shale / Ohio Shale (middle Polygnathus varcus zone, Givetian Stage, upper Middle Devonian) over the Boyle Formation (lower Polygnathus varcus zone, Givetian Stage, upper Middle Devonian)
Locality: Drowning Creek East outcrop - roadcut along the northern side of Route 52, east of Drowning Creek, far-western Estill County, east-central Kentucky, USA (37° 42' 41.30" North latitude, 84° 05' 01.40" West longitude)
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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.
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