Named the Shippensburg formation in south-central PA and western MD for Shippensburg, Franklin Co., PA. Consists of five distinct limestone types: dark gray, fine-grained, and cobbly limestone; dark gray, fine-grained, and evenly bedded limestone; medium to coarse calcarenite; interbedded dark gray, medium-grained limestone and calcilutite pellet conglomerate; and dove colored calcilutite. Seven metabentonites recognized in eastern belts of outcrop (not all present in one section). In western belts, subdivided into (ascending) Pinesburg, Fannettsburg, and Doylesburg members. Thickness is 416 feet at type locality, and thins to northeast, south, and west. Unconformably overlies "Stones River" limestone and unconformably underlies Mercersburg formation. Lower contact poorly exposed and marked only by contrasting lithologic character. Upper contact marked by lithologic change and a prominent irregular partially silicified bedding surface. Unit extends into western MD. The Shippensburg is of Middle Ordovician age.

Source: GNU records (USGS DDS-6; Reston GNULEX).