Outcrop Analog for Lower Paleozoic Hydrothermal Dolomite Reservoirs, Mohawk Valley, New York
Brian Slater, Langhorne Smith, Richard Nyahay, Reservoir Characterization Group, New York State Museum, Albany, NY, 12230
Geochemical analysis and field relations of the Palatine Bridge dolomite outcrop in the Mohawk Valley of New York suggest that it has undergone significant fault-related hydrothermal diagenesis. This study focuses on fluid inclusion, stable isotope, 3D-Ground penetrating radar, core analysis, and surficial observation which all show a link between faulting, dolomitization, and other hydrothermal alteration. It is a scaled analog for Trenton / Black River hydrothermal dolomite reservoirs of the eastern United States. The outcrop is in the Lower Ordovician Tribes Hill Formation, which is an early Ordovician shaley limestone.
The outcrop has an en-echelon fault, fracture and fold pattern. Geochemical analysis, though helpful in characterizing the conditions of formation, do not define its origin absolutely. A 3-D ground penetrating radar survey of the quarry floor has helped to map out faults, fractures, anticlines, synclines and the extent of dolomitization. Most of the dolomitization occurs in fault-bounded synclines or "sags". The dolomite structures are highly localized, occurring around the faults and are absent away from faults and fractures. Trenches cut across the outcrop help relate offset along faults to the overall geometry of the dolomitized bodies. Comparison of the Palatine Bridge outcrop to producing hydrothermal dolomite reservoirs reveals significant similarities. Although the outcrop is much too small and shallow to act as a producing gas field, it may be studied as a scaled analog to help petroleum geologists characterize existing gas plays and prospect future areas of exploration.
AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York