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Mohawk Valley Exposures as Outcrop Analogs for the T/Br Finger Lakes Play, New York State

Paul A. AGLE1; Robert D. JACOBI1; Charles E. MITCHELL1

1University at Buffalo, UB Rock Fracture Group, Buffalo, NY 14260

Outcrops of the Cambro-Ordovician section in the Mohawk Valley may be an analog for the subsurface T/Br play in the Finger Lakes (NYS) region of the Appalachian Basin. Dolomitization and faulting commonly occur in the Little Falls region of the Mohawk valley. Slickenlines, drag folds, and outcrop patterns indicate that the northerly-striking faults are dominantly dip-slip. Some WNW-striking faults in the region are short lateral ramps that link northerly trending faults, whereas others appear to extend across the northerly trending faults.

Outcrop analysis of faulting, fracturing, veining, and other mineralization features in the Mohawk Valley show that the faults of the study area have acted as fluid conduits. Along NNE-trending splays of the Little Falls Fault, a significant increase in mineralization features (vugs, veins, incipient breccia, dolomitized limestone) is observed within 200m of the fault. The mineralization events also bear a Mississippi Valley Type (MVT) signature. Along the N-trending Dolgeville Fault, the mineralization zone is more restricted (<100m).

Veins occurring in stratigraphically low units near the Little Falls Fault strike parallel with the fault plane, whereas veins occurring higher in the section near the Dolgeville Fault strike nearly perpendicular to the fault plane. This change in orientation can be related to a tectonic model wherein the faults in earlier Taconic times in this region were extensional, related to stretching of the craton over the peripheral bulge and into the trench, whereas in later Taconic times, the stress field would have rotated in response to the jammed subduction zone.

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York