Altitude and configuration of the potentiometric surfaces of the upper and lower aquifer systems in Bridgeton, Nockamixon, and Tinicum Townships, Bucks County, Pennsylvania, April 1991 through April 1992

The mapped area in underlain by layered sedimentary rocks chiefly consisting of shale, mudstone, siltstone, and argillite and by a diabase sheet thtat has intruded the sedimentary rocks.  The sedimentary rocks adjacent to the diabase are thermally altered to hornfels.  Water levels in shallow wells completed in the diabase indicate the presence of an upper, shallow aquifer system.