New England Oroclines
Orocline formation in the southern New England Orogen is generally agreed as having occurred during a Permian hiatus in continental arc magmatism during west-(continent) dipping subduction along the Gondwana palaeo-Pacific boundary. The evolution of ideas culminating in the formation of present day models of oroclines in the New England Orogen has been presented by Murray (1997). Despite consensus on the age of oroclinal folding, there is little agreement on the dynamics of their formation, especially since the southern pair has an opposite movement sense to the northern pair.
Models may be grouped into 2 types: i) formation as megafolds inboard of a major N to NNW-trending shear zone with either a sinistral (Cawood 1982, Cawood and Leitch 1985; Cawood et al. 2011a; Collins et al. 1993) or dextral sense of shear (Murray et al. 1987; Offler and Foster 2008); and ii) formation in a composite model, whereby an original irregular plate margin or variation in plate boundary rollback velocities was accentuated by a dextral movement sense on an offshore megashear followed by east-west contraction (Li et al. 2011; Rosenbaum et al. 2012).