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A reconnaissance grid of 550 mi of Vibroseis data extending from northernmost Vermont to slightly north of Albany, New York, provides a framework for analyzing subsurface structure and stratigraphy of eastern New York and western Vermont.
Regional stratigraphic analysis based on outcrop sections indicates northward and eastward thickening of the Cambrian-Ordovician shelf sequence. Synthetic seismograms from wells in Quebec and southwestern Washington County, New York, document this change in the subsurface and correlate the seismic stratigraphy. Seismic data indicate thickening occurs north of the "Whitehall culmination," an approximately 40-mi long buttress area of Adirondack Grenville basement. Changes in thickness appear to be gradual and not fault controlled.
Foreland thrust systems of New York and Vermont relate via a displacement transfer or lateral ramp zone associated with the "Whitehall culmination." Both thrust systems accomplish final emplacement of metamorphic sheets, deform them, and transport shelf material, which is predominantly shale in New York with increased percentage of carbonates in Vermont. Deflection of several major structural elements illustrates the culmination's buttress effect.
Subsurface structural elements in New York include western graben, central horst block, and eastern fault-zone trends. No analogous trends have been identified in Vermont where predominant faulting is down-to-the-east. Significantly, in southwestern Washington County, New York, preexisting horst blocks do not serve as ramps to deflect thrusts upward. Instead, the Snake Hill-Smiths basin and Schuylerville thrusts shear off the upper sedimentary sequence of the horst and transport it westward.
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