Active tectonics in Northern Victoria Land (Antarctica) inferred from the integration of GPS data and the geologic setting

A semi-permanent global positioning system (GPS) network of 30 vertices known as theVictoria Land Network for Deformation Control (VLNDEF) was set-up in the Austral summer of1998 in Northern Victoria Land (NVL), including Terra Nova Bay (TNB), Antarctica. Thelocations were selected according to the known Cenozoic fault framework that is characterizedby a system of NW-SE regional faults with right-lateral, strike-slip kinematics. The TNB1permanent GPS station is within the VLNDEF, and following its installation on a bedrockmonument in October 1998 it has been recording almost continuously. The GPS network hasbeen surveyed routinely every two summers, using high-quality, dual-frequency GPS receivers.In this study, we present the results of a distributed session approach applied to the processing ofthe GPS data of the VLNDEF. An improved reference frame definition was implemented,including a new Euler pole, to compute the Antarctic intra-plate residual velocities. Theprojection of the residual velocities on the main faults in NVL show present-day activities forsome faults, including the Tucker, Leap Year, Lanterman, Aviator, and David faults, with rightlateralstrike-slip kinematics and local extensional/ compressional components. This active faultpattern divides NVL into eight rigid blocks, each characterized by their relative movements andrigid rotations. These show velocities of up to several mm/yr, which are comparable to thosepredicted by plate tectonic theory at active plate margins

Long-lived orogenic construction along the paleo-Pacific margin of Gondwana (Deep Freeze Range, North Victoria Land, Antarctica)

The paleo-Pacific margin of Gondwana records a prolonged history of convergence during the Cambrian-Early Ordovician Ross-Delamerian and the Middle Ordovician-Early Silurian Lachlan orogenies. This study describes structure, petrology, and geochronology of a set of NW-SE striking ductile shear zones that crosscut the Ross age, Early Cambrian granitoid rocks of the Wilson Terrane in the Deep Freeze Range (North Victoria Land, Antarctica). The shear zones developed under amphibolite facies metamorphic conditions (650-700C and 0.5-0.7 GPa) and show a systematic top-to-the-NE sense of shear. The shear zone activity interferes with emplacement of late, subhorizontal leucocratic dikes and combined U-(Th)-Pb (zircon and monazite) and 40Ar-39Ar (biotite and phengite) geochronology constrains the shearing event at ∼470 Ma, with the sheared granite yielding U-Pb zircon crystallization ages of ∼508 Ma. The reconstructed P-T path followed by the granite protoliths indicates an anticlockwise trajectory, suggesting the synshearing amphibolite metamorphism was associated with the burial of an early formed, Ross continental crustal section. These new findings are interpreted as evidence of a renewed, Ordovician episode of orogenic construction at the paleo-Pacific margin of Gondwana that predated the onset of the Lachlan orogeny in the region. A polycyclic reactivation of the Ross age Wilson Terrane of North Victoria Land is suggested, which is used to propose a unitary framework for the space-time transition from the Ross-Delamerian to the Lachlan orogeny along the proto-Pacific active margin of Gondwana. Copyright 2011 by the American Geophysical Union