Geological Relationships at Cotton Plateau, Nimrod Glacier Area,
Bearing on the Tectonic Development of the Ross Orogen,
Transantarctic Mountains, Antarctica

E. Stump¹*, D.G. Edgerton² & R.J. Korsch³

¹Department of Geological Sciences, Arizona State University, Tempe, Arizona 85287-1404 - U.S.A.
²L. Robert Kimball & Associates, 1580 Reed Road, Suite C-3, Pennington, New Jersey 08534 - U.S.A.
³Australian Geological Survey, G.P.O. Box 378, Canberra City, A.C.T. 2601 - Australia

Received 5 June 2001; accepted in revised form 6 December 2001
 

Abstract - At the northern end of Cotton Plateau Lower Cambrian Shackleton Limestone occurs in discordant contact with clastic sedimentary rocks of Goldie Formation.  The overlying Shackleton Limestone is interpreted to contact Goldie Formation with angular unconformity.  Two episodes of deformation are recognized in Goldie Formation.  The first is characterized by moderately to steeply plunging mesofolds with mica growth defining axial plane cleavage (S₁). Following erosion and deposition of Shackleton Limestone, a second episode of deformation focused in a steep shear zone cutting Goldie Formation and folding Shackleton Limestone into an open syncline with subhorizontal axis.  This deformation also formed a fracture and crenulation cleavage (S₂), which overprinted the earlier (S₁) cleavage of Goldie Formation and is parallel to the axial plane of the Shackleton syncline.  The structural data support prior models which have suggested oblique impingement during the Neoproterozoic or earliest Cambrian of a terrane or microcontinent in the central Transantarctic Mountains (prior to deposition of Shackleton Limestone), followed by subduction leading to the main phase of the Cambro-Ordovician Ross orogeny. It is proposed that the term ìBeardmore orogenyî be renamed the ìBeardmore eventî.

*Corresponding author (ed.stump@asu.edu)