Main Andean sinistral shear along the Cooper Bay Dislocation Zone, South Georgia?
The Cooper Bay Dislocation Zone (CBDZ) represents a major NW-SE trending tectonic boundary within the island of South Georgia that juxtaposes components of a Middle Jurassic to mid-Cretaceous island-arc and back-arc-basin system. New detailed structural data from the southern end of the dislocation zone reveal that earliest displacement along the boundary appears to have been associated with dip-slip reverse shear, characterised by widespread proto- to meso-mylonitic granitic rocks within the basement assemblage exposed to the southwest of the shear zone. Along the northeast margin, highly sheared and mylonitised metasedimentary and metabasic rocks reveal sinistral strike-slip kinematics and a sub-horizontal mineral lineation. Narrow zones of sinistral shear are locally superimposed within the basement rocks along the SW margin, that together with the presence of brittle sinistral faults suggest that the strike-slip component of deformation postdates the dip-slip. Comparison with the tectonic history of the Rocas Verdas Marginal Basin, Fuegian Andes, suggests that the sinistral shear event preserved along the CBDZ maybe be related to Late Cretaceous, main Andean orogenic transpression, although a Cenozoic event cannot to ruled out.
In: Cooper, A.K., Raymond, C.R., ISAES Editorial Team, . (eds.). Antarctica: a keystone in a changing world. Online proceedings of the 10th International Symposium on Antarctic Earth Sciences, Santa Barbara, California, August 26 - September 1, 2007, U.S. Geological Survey and National Academies Press, 4 pp.