STRUCTURAL AND STRATIGRAPHIC RELATIONSHIPS NEAR THE MARTINSBURG-SHAWANGUNK CONTACT

Attempts to accurately describe the complex geology around Blue Mountain, Kittatinny Ridge, and Shawangunk Mountain in Pennsylvania, New Jersey, and New York have been numerous (e.g. Drake, 1952, Wright et al, 1979, and Epstein, 1993). Many hypotheses have been put forth concerning how the deposition and deformation of these rocks chronicle the sequence of tectonic events during the Taconic Orogeny (e.g. Epstein and Lyttle, 1987, Dorsch et al, 1994, and Ganis and Wise, 2008). This project specifically aims to characterize the nature of the contact between the Martinsburg and Shawangunk Formations in order to relate observed structural and sedimentary relationships to Paleozoic orogenic events.

Field mapping near the Martinsburg-Shawangunk contact between Port Clinton, PA and Poughkeepsie, NY has resulted in a record of stratigraphic and structural relationships across this lithostratigraphic boundary. Of particular interest is the nature of the contact, along which evidence for stratigraphic conformity, unconformity, and fault contact exists.

Completed field work has confirmed many of the stratigraphic and sedimentologic descriptions of the Martinsburg and Shawangunk Formations reported in literature. Work to date suggests that the nature of the contact between these formations does not vary in a consistent manner along strike. From north to south, the angular unconformity of the contact varies from 21 degrees near Minnewaska State Park in southeastern New York to zero degrees around Bangor, PA. It then increases again to approximately 15 degrees at Lehigh River Gap, where there is also evidence of dip-slip faulting at the contact.

Methods for high-resolution digital mapping are currently being explored. These techniques employ high resolution (~ 1 meter / pixel) Lidar data and derivatives including slope, aspect, and hillshade topographic maps. These methods have the potential to reveal locations of interest prior to actual field-checking and may allow for digital measurement of structural elements.