When published structure contour maps of the Devonian outcrop, Tully formation, base Hamilton Group, and Oriskany Sandstone are overlain, the locations and trends of anticlinal and synclinal axes are not coincident, suggesting a lack of vertical continuity. The traces of fold axes within these specific stratigraphic units and their vertical orientation are not well defined by previous work.

In order to develop a cohesive, three-dimensional structural model for the Trenton Group (Middle Ordovician) through the Tully formation (Middle Devonian) interval, seismic surveys from six prospect areas in the southern tier were interpreted and well data from over 2,000 wells were used to make computer-drawn geologic structure and isopach maps as well as cross sections. The stratigraphic framework of such an analysis is built upon the strong seismic reflectors, in this case carbonates, specifically the Tully formation, Onondaga Formation, Lockport Group, and Trenton Group.

Subsurface facies were identified for the thickest intervals, namely the Hamilton, Salina, Lockport, and Clinton Groups, as well as the Queenston-Oswego-Lorraine sequence. The lithologic facies analysis is then used in conjunction with the seismic sections to define seismic facies. The importance of seismic facies is that they may reveal how certain lithologies deform in the stack of

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subsurface sedimentary layers.

Seismic mapping indicates much greater variation of near-surface horizons than mapping with well data. Axial planes of Acadian folds appear to be vertical. Fold amplitude diminishes between the Tully formation and the Lockport Group in some areas, while in other areas amplitude remains constant through the Devonian and Silurian section. In Chautauqua County, an anomalously thick Onondaga to Lockport interval parallel to regional fold axes has been interpreted as an anticline with a salt core, suggesting decollement tectonics.

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