TRANSPRESSION AND EXTRUSION IN SOUTH-CENTRAL NEW ENGLAND RESULTING FROM LATE PALEOZOIC OBLIQUE COLLISION

The Bronson Hill zone in southern New England includes a range of structures that record markedly different states of finite strain suggestive of contraction, wrenching, and extension that conform to models for transpression in a mid-crustal setting. The metaplutonic Monson gneiss can be broadly characterized by N-S striking, subvertical to steeply inclined S>L tectonites, subvertical (locally subhorizontal) stretching lineations, dextral and reverse kinematic indicators, and coplanar isoclinal folds. The Monson gneiss is bounded by conjugate high strain zones characterized by subvertical to steeply inclined mylonitic foliations, a range of lineations, and well-developed kinematic indicators (sinistral/normal on the west: Mount Dumplin high strain zone; dextral/reverse on the east: Conant Brook shear zone). There is a distinct lack of overprinting and physical relationships suggest all structures were developed contemporaneously. New SIMS and in-situ EPMA monazite geochronology, in addition to existing data, confirm coeval development of structures at 330-300 Ma and indicate bulk dextral transpression. Transpressional deformation was partitioned macroscopically and meso-/microscopically in response to lithological, structural, and rheological discontinuities. Between these scales of observation, deformation is quasi-homogeneous within kilometer-scale domains and can be compared with various theoretical models of transpression zones, while strain compatibility problems between neighboring domains was maintained by heterogeneity at larger and smaller scales.