"Mining's In Their Veins" A March, 2004 article about the Shingara family from Trevorton PA (modified to .pdf format, by permission of Bevin Milavsky, The Daily Item).
Stratigraphy of central PA
This diagram represents the sedimentary strata beneath the Lewisburg-Milton area in central Pennsylvania as measured Richard Nickelsen, Geology Professor emeritus at Bucknell. Oldest strata is at the bottom. Each Formation's resistance to erosion is shown by how far it "juts out" to the left (the Tuscarora Formation is very resistant and holds up many of the ridges in central PA).