Cenozoic tectonic lineaments of the Terra Nova Bay region, Ross Embayment,Antarctica

The Cenozoic tectonic framework of the Terra Nova Bay region is dominated b y NW-SE-trending dextral strike-slip faults that represent the onshore expr ession of dextral transform shear along the Tasman Fracture Zone and Ballen y Fracture Zone in the Southern Ocean. These intraplate faults reactivated inherited, Paleozoic crustal discontinuities established during the Ross Or ogeny. Cenozoic, N-S to NNE-SSW transtensional faults developed in the crus tal blocks in between the strike-slip faults as a kinematic consequence of the transcurrent motion. These transtensional faults provided a suitable me chanism to accomplish for dextral horizontal throw along the NW-SE strike-s lip faults. The complex, strike-slip-induced kinematics controlled the loca tion and the emplacement mechanisms of Cenozoic basic magma in the coastal sector of the Terra Nova Bay region. Sequential restoration of the present- day fault pattern in the Terra Nova Bay region, allowed reconstruction of t he geologic framework of the area prior to onset of the strike-slip activit y (from 105 Ma to 32 Ma), and also before the opening of the Ross Sea (earl ier than 105 Ma). The pre-extensional framework was dominated by a vast, fl ay-lying plateau, mainly made up by the Jurassic Ferrar Supergroup rocks. C rustal thinning occurred due to movement on NNE-SSW- to NE-SW-trending exte nsional faults, and the inherited, through-going Paleozoic NW-SE regional-s cale discontinuities were reactivated as transfer faults. Main extensional faults in the western side of the Ross Sea dip to the NE, and segmented thi s region into a series of blocks with minor tilting. Strike-slip tectonics characterises Late Cenozoic time, and is responsible for N-S extensional, r ather symmetrical faulting along transfer zones in between major NW-SE tran scurrent faults. Intersections between these two trends eased deep magma ri se and the development of long-lasting, central volcanoes. The morphologica l effects of the last tectonic event were the development of NW-SE and N-S depressions and the rapid growth of volcanic edifices, that influenced both location and orientation of the main glaciers in northern Victoria Land an d are responsible for their characteristic zig-zagging. (C) 1999 Elsevier S cience B.V. All rights reserved.