987565 Deformation in the Appalachian Foreland: Detachment Structures in the Basal Marcellus Shale, Central New York

Décollement zones within the organic-rich black shale members of the basal Marcellus Formation in New York and Pennsylvania have been recognized for some time (Nickelsen, 1986; Evans, 1994, among others). Outcrop study of the upper Onondaga Formation-Marcellus Formation contact at three localities in the central New York outcrop belt (Figure 1) demonstrates that thrust fault structures are present. Given recent interest in the Marcellus as a gas shale reservoir, the relationships among faulting, fracturing, fluid migration, vein mineralization and hydrocarbon maturation in these zones may provide additional insights as resource development proceeds. In addition, the décollement zones are intensely fractured and may serve as attractive targets for horizontal well development. The thrust fault systems described here were active during hydrocarbon maturation in the Marcellus, and are most likely the result of regional deformation in the Appalachian Foreland during the Alleghanian Orogeny.