Stratigraphy and Structure of the Southern Prince Charles Mountains, East Antarctica
G. Phillips1*, C.J.L. Wilson1 & I.C.W. Fitzsimons2
1School of Earth Sciences, University of Melbourne, 3052 Parkville, Victoria – Australia
2Tectonics Special Research Centre, Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845 – Australia
Received 22 April 2005; accepted in revised form 3 October 2005
Abstract - Stratigraphic and structural data support the existence of a thick and extensive low-grade sedimentary cover sequence of relatively young age at Cumpston Massif and Mount Rubin compared with the underlying Archaean-Palaeoproterozic basement rocks of the southern Prince Charles Mountains. The stratigraphy of these sequences suggests sediment deposition was within a shallowing-up marine basin. Folding within the basin displays a simple structural style in comparison to older, multiply deformed rocks in the adjacent nunataks such as Mount Stinear and Mount Ruker. D1 folding and fabric development within the basin has formed in response to a northeast-southwest shortening. This stress regime may be responsible for late stage mylonite zones, thrust faults and transposed fabrics that overprint earlier structures in the basement that represent the basin margins. At Cumpston Massif, the base of the basin sediments is incorporated into a 100 m wide low-angle shear zone, with the meta-sediments ramping over deformed felsic gneiss. Similar relationships at Mount Maguire suggesting continuation of the basin further south, yet absent at Mount Rubin, creating uncertainties in extrapolating basin margins to the west. Early deformation within basement sequences prior to basin deposition suggests at least two phases of non-coaxial deformation, preserved in the folded banded iron formations at Mount Ruker. Such structures are partially obscured at Mount Stinear due to mylonitisation, and possible exhumation of the underlying crystalline basement.
*Corresponding author (g.phillips2@pgrad.unimelb.edu.au)