Cenozoic geodynamics of the Ross Sea region, Antarctica: Crustal extension, intraplate strike‐slip faulting, and tectonic inheritance

Abstract

An integrated study of onshore and offshore geology of the Ross Sea region (namely, Victoria Land, north of Ross Island, and the Ross Sea, Antarctica) has revealed a complex, post‐Eocene tectonic framework. Regional NW‐SE right‐lateral, strike‐slip faults are the outstanding feature of this framework and overprint an older Mesozoic extensional event, responsible for formation of N‐S basins in the Ross Sea. The Cenozoic framework includes kinematic deformation and reactivation along the NW‐SE faults, including formation of pull‐apart basins, both positive and negative flower structures, and push‐up ridges. N‐S extensional faults are well developed between NW‐SE faults and indicate E‐W extension during the Cenozoic, produced by the NW‐SE right‐lateral strike‐slip motion together with regional crustal extension. NNW‐SSE compression, induced by the right‐lateral, strike‐slip kinematics, is indicated by locally inverted NE‐SW faults and basins. The evolution, geometry, and location of the Rennick Graben and the Lanterman Range fit well into this model. Variations in the deformational style across the region can be linked to corresponding variations in the bulk crustal rheology, from brittle behavior in the west, to ductile deformation (at subseismic‐scale resolution) near the Eastern Basin. A semibrittle region that favors N‐S clustering of Cenozoic magmatic activity lies in between. In this region, Cenozoic volcanoes develop at the intersections of the NW‐SE and the major N‐S faults. The NW‐SE faults cut almost continually from the Ross Sea to East Antarctica through lithospheric sectors with different rheology and thickness. At least two of the NW‐SE faults correspond to older Paleozoic terrane boundaries in northern Victoria Land. The NW‐SE faults link in the Southern Ocean with major transform faults related to the plate motions of Australia, New Zealand, and Antarctica.