The Martinsburg formation consists of a thick series of shales and sandstones of upper Trenton and Cincinnatian age. Within the main belt of the Martinsburg in the Lehigh and Lebanon valleys of eastern Pennsylvania (Fig. 1) are many exposures of unfossiliferous limestone varying in thickness from a few inches to 160 feet. In a number of places the limestone is sufficiently abundant and of such a quality as to have permitted quarrying for lime or for road metal. Eighteen such limestone areas appear on the Geologic Map of Pennsylvania (1931). In a comprehensive paper discussing general Martinsburg relations, Stose and Jonas1 mention several of these areas near the Schuylkill River and interpret them as anticlines of the Leesport limestone, exposed by erosion of the overlying shale. They also consider other areas shown on the state geologic map to be anticlinal inliers of Leesport.2 On the other hand, Behre 3 . . .