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OUTSTANDING GEOLOGIC FEATURES OF PENNSYLVANIA
WHALEBACK
NORTHUMBERLAND COUNTY
Location
Bear Valley strip mine, near Shamokin, Northumberland Co. Coal
Twp., Shamokin 7.5-minute quadrangle
Geology
The Whaleback is a rare and one of the best three-dimensional
exposures of folded rocks in the nation, and is considered to be
the classic field example of style and mechanics of structural
development of the central Appalachians. Structural elements,
including joints, cleavage, slickenlines, lineations, folds, and
three types of faults, and six stages of deformation for the Ridge
and Valley physiographic province, are visible at this former
strip-mine. The site is privately owned; however, part of the
Whaleback is visible from the adjacent ATV park.
Looking southwest. Note people on Whaleback for scale. The floor of the mine is the surface of a single deformed bed that was under
the coal. The geologic unit is the Pennsylvanian age Llewellyn Formation. Photograph by Gary Fleeger, Pa. Geological Survey.
Recommended Reading
References: Nickelsen, R.P., 1979, Sequence of structural stages of the Allegheny orogeny, at the Bear Valley strip mine,
Shamokin, Pennsylvania: American Journal of Science, v. 279, p. 225–271.
Eggleston, J.R., and Edmunds, W.E. (field trip leaders), 1984, Anthracite basins of eastern Pennsylvania, field trip
guidebook T242, 28th International Geological Congress, guidebook, 29 p.
For information regarding outstanding geologic features, contact the Pennsylvania Geological Survey:
Bureau of Topographic and Geologic Survey, 3240 Schoolhouse Rd., Middletown, PA 17057
717-702-2017 www.dcnr.state.pa.us/topogeo Also see Anthracite Outdoor Adventure Area web site
S. Reese, 2014