Brittle architecture of the Lanterman Fault and its impact on the final terrane assembly in north Victoria Land, Antarctica

Abstract

Abstract: The Lanterman Fault is one of the subvertical, NW–SE-striking intraplate shear zones that bound the major Proterozoic to Early Palaeozoic tectono-metamorphic blocks constituting north Victoria Land, Antarctica. This fault zone, several kilometres wide and with an onshore along strike length of about 400 km from the Southern Ocean to the Ross Sea, records almost entirely brittle deformation, producing complex, NW–SE- to north–south-trending, anastomosing dextral fault strands. Brittle faulting is subparallel to the regional subvertical schistosity, indicating that it was superimposed in a broad region that has earlier experienced ductile-dominated deformation. The regional-scale brittle deformation fits into a general kinematic model involving progressive NW–SE dextral simple shear. Two major onshore age constraints exist for brittle faulting along the Lanterman Fault system: (i) involvement of Triassic Beacon and Jurassic Ferrar rocks in faulting; and (ii) the intimate link between right-lateral faulting and Cenozoic magmatism along the southern onshore termination of the fault. We infer that final terrane assembly in northern Victoria Land was the response to late-stage (Cenozoic) right-lateral movements along NW–SE inherited structures, rather than being the result of accretion during the Early Palaeozoic Ross Orogeny.