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

2Vermont Geological Survey, Waterbury, VT 05671-2420

It is well established that the Trenton/Black River experienced fluid migration and mineralization that resulted in reservoir development in central NYS. Yet, in the Mohawk Valley and western Vermont, older carbonate units exhibit extensive dolomitization. For example, in the Mohawk Valley faulting and dolomitization is prevalent in units of the Cambro-Ordovician Beekmantown, and some of these events are thought to be a separate event from those phases in the Trenton/Black River.

The fault activity for the initial development of the Trenton/Black River is likely Taconic, based on the seismic records that show infilling of the grabens in post Trenton time. Models suggest that both peripheral bulge faulting when the continental plate was under extension, and later faulting when the plate was under collisional compression can account for the faulting of classic Taconic time. But what explains the intra-Beekmantown faulting? That time is known from Vermont to be the time of initiation of subduction. We suggest that initiation of subduction processes promoted deep faulting in the leading edge of the continental plate, as well as at the site of subduction initiation.

In western NYS the Silurian Lockport Formation is pervasively dolomitized with MVT deposits. The dolomitization/MVT deposits probably are related to active faulting that penetrated the basement during development of the Silurian Appalachian basin. This faulting and basin development may be related to ridge subduction beneath Laurentia.

The Devonian Onondaga and Tully were not dolomitized––possibly because of changed stratigraphic/structural conditions, including the Silurian salt blanket below and the black shales above.

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