This Appalachian cross section and text,
paper version published in 1992, is now available online:
U.S. GEOLOGICAL SURVEY BULLETIN 1839-K
Stratigraphic Framework of Cambrian and Ordovician
Rocks in the Central Appalachian Basin from Medina County, Ohio, through
Southwestern and South-Central Pennsylvania to Hampshire County, West Virginia
By Robert T. Ryder, Anita G. Harris, and
John E. Repetski
Revised and digitized by Robert D. Crangle,
Jr.
http://pubs.usgs.gov/bul/b1839k/