The Shawangunk Formation (Upper Ordovician(?) to Middle Silurian) in eastern Pennsylvania

Professional Paper 744
Work done in cooperation with the Pennsylvania Department of Environmental Resources Bureau of Topographic and Geological Survey
By:  and 



The Shawangunk Formation of Early and Middle Silurian age, and possibly Late Ordovician age, in eastern Pennsylvania and northwestern New Jersey forms a thick clastic wedge of sediments derived from sourcelands to the southeast uplifted during the Taconic orogeny. The formation is divided into four newly denned members, from bottom to top: Weiders Member (coarse conglomerate and quartzose sandstone), Minsi Member (quartzose conglomeratic sandstone and minor argillite), Lizard Creek Member (complex sequence of quartzose sandstone, siltstone, shale, and a few red beds, with sparse fauna), and Tammany Member (quartzose conglomeratic sandstone and minor argillite). The Weiders Member pinches out to the east near Smith Gap. The Tammany Member cannot be conveniently mapped west of Smith Gap because of interfingering with and replacement by beds of the Lizard Creek Member. The contact of the Shawangunk with the underlying Martinsburg Formation is an angular unconformity. The boundary between the Shawangunk and overlying Bloomsburg Red Beds is irregular and transitional through about 130-700 feet of red, green, and gray rocks. Sedimentary features in the Shawangunk indicate that the sediments were deposited by streams and in a complex transitional marinecontinental environment, including tidal flats, barrier bars, estuaries, and lagoons.

Study Area

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title The Shawangunk Formation (Upper Ordovician(?) to Middle Silurian) in eastern Pennsylvania
Series title Professional Paper
Series number 744
DOI 10.3133/pp744
Year Published 1972
Language English
Publisher U.S Government Printing Office
Publisher location Washington, D.C.
Description iv, 45 p.
Country United States
State Pennsylvania
Other Geospatial Shawangunk Formation