Thursday, 30 August 2007 - 3:40 PM
4.P2.B-1
Main Andean sinistral shear along the Cooper Bay Dislocation Zone, South Georgia?
Michael L. Curtis, Geological Sciences Division, British Antarctic Survey, High Cross, Madingley Road, Cambridge, NN14 4LS, United Kingdom
The Cooper Bay Dislocation Zone (CBDZ) represents a major NW-SE trending tectonic boundary within South Georgia that juxtaposes components of a Middle Jurassic to mid-Cretaceous island-arc and back-arc-basin system. New structural data from the southern end of the CBDZ indicates that its earliest displacement was associated with dip-slip reverse shear, characterised by heterogeneously mylonitised granitic rocks exposed along the southwest margin of the shear zone. Along the northeast margin, mylonitised and sheared metasedimentary rocks reveal sinistral strike-slip kinematics. Sinistral strike-slip deformation continued during uplift into the brittle deformation regime suggesting it postdated the reverse shear event. Comparison with the tectonic history of the Rocas Verdas Marginal Basin, in the 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 at this time.