Abstract The Trenton Limestone of West Virginia was deposited on a gentle carbonate ramp that sloped eastward into a deep foreland basin. Unlike many limestones this unit formed during an early stage of orogeny, is transgressive in nature, and accumulated during a large influx of shale. Initial uplift of an eastern fold-thrust belt, created as the North American plate collided with a volcanic-arc system, led to lithospheric flexure and downwarping of the foreland basin under the load of an accreted terrane. Basin subsidence was rapid, being fast enough to outpace sedimentation but not so fast as to suppress carbonate sedimentation under deep, anaerobic conditions. Thus, limestone deposition continued, although with a deepening-upward sequence. Introduction of terrigenous mud was discontinuous through time, which generated a periodicity to the limestone and shale interbedding. These muds did temporarily downgrade or eliminate skeletal lime production, especially to the east where shale influxes were greater. With each return to clear water, however, carbonate deposition resumed. Eventually plate convergence and uplift of the source area proceeded to the point where clastic deposition overwhelmed the carbonate ramp. Trenton sedimentation then gave way to the flysch wedge of the overlying Martinsburg Formation. Thus, the relationship in space and time between subsiding basin and rising orogenic landmass exerted a major influence on the Trenton’s internal stratigraphy and facies development.

Abstract Harpers Ferry is located at the confluence of the Potomac and Shenandoah Rivers where the Potomac has cut an impressive water gap through the Blue Ridge. Three states—West Virginia, Virginia, and Maryland—meet at this point, which is located on the Harpers Ferry 7½-minute Quadrangle. Access to Harpers Ferry from the east or west is by way of U.S. 340 (Fig. 1). Recommended stops are along U.S. 340 south of the Potomac River, Sandy Hook Road north of the Potomac, and the B&O Railroad tracks and within Harpers Ferry National Historical Park (Fig. 2).