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.
Additional Publication Details
USGS Numbered Series
Main Andean sinistral shear along the Cooper Bay Dislocation Zone, South Georgia?