Development and inversion of the Mesozoic Victoria Basin in the Terra Nova Bay (Transantarctic Mountains) derived from thermochronological data

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The Terra Nova Bay region of the Transantarctic Mountains hosts three N–S to NNW–SSE extending mountain ranges, Deep Freeze Range, Eisenhower Range and northern Prince Albert Mountains. All ranges consist of basement rocks locally overlain by Permo-Triassic sediments and Jurassic volcanic rocks. Recent thermochronological studies recognized that the Eisenhower Range was originally covered by a kilometre-thick Jurassic–Eocene sedimentary sequence. Here we present a comprehensive apatite fission track (AFT) and U-Th-Sm/He (AHe) data set of vertical sample profiles from the Terra Nova Bay to reconstruct architecture, extension and geometry of this depocentre and place its evolution in the context of supraregional geodynamic processes. The study comprises new data and thermal history models from the Deep Freeze Range and new thermal history models of published data from the northern Prince Albert Mountains.New AFT and AHe ages of 25–275Ma from the Deep Freeze Range correlate tightly with sample elevations. Thermal history modelling of these data and complementary proxies detects common heating of the Jurassic surface and rapid late Eocene cooling. Regression of vertical paleotemperature profiles reveals an increased Jurassic and a moderate Cretaceous–Eocene geothermal gradient of 45° and 25°C/km, respectively. Paleotemperatures and gradients used in tandem infer basement burial increasing from ~2km in Deep Freeze and Eisenhower Ranges to ~3.4km in the Prince Albert Mountains. Such a varying overburden probably reflects regional differences in the Jurassic basement topography. Subsequently, sediment thickness uniformly increased in the order of 1km until late Eocene. Mid-Jurassic basin initiation and subsequent sediment accumulation is explained by extension of a Mesozoic Victoria Basin during Gondwana breakup between Antarctica and Australia. Late Eocene/early Oligocene basin inversion is associated with the formation of the West Antarctic Rift System while differential final exhumation represents the change from downwearing to backstepping incision.