FRACTURE, VEIN AND FAULT INTERRELATIONSHIPS WITHIN THE UTICA SHALE, MOHAWK VALLEY, NEW YORK: IMPLICATIONS FOR TECTONIC MODELS
Mohawk Valley field data support tectonic models for the Taconic Orogeny that begin with the formation of N and NNE-striking fault systems within a syndepositional extensional basin. Extension facilitated the development of a dominant NNE-striking vein-filled fracture set in the Utica Shale. Extension was followed by a westward directed σHmax resulting in younger ENE and WNW-striking conjugate shear fracture sets and E/W-striking mode 1 fracture sets. The west-directed σHmax is consistent with earlier suggestions that final Taconic collision resulted in the formerly normal faults converting to high angle reverse faults. ENE right lateral vein-filled shear fractures are also consistent with Taconic escape tectonics related to the New York promontory. Rarely observed E/W and NNW vein-filled fracture sets with inferred conjugate shear indicate that a later NW-oriented σHmax developed within the basin. This conjugate shear set may have resulted from the NW-directed collisional phase of the Alleghanian Orogeny.