Fission-track geochronology, tectonics and structure of the transantarctic mountains in Northern Victoria land, antarctica

A regional fission-track dating study in northern Victoria Land (NVL) provides information on the amount, timing and variable rates of uplift of the Transantarctic Mountains (TAM) at their northernmost extent. Apatite ages increase systematically with elevation and together with confined track length distributions, define a two-stage uplift history, although a variety of thermal histories, resolvable by use of confined track length distributions, exist for different parts of NVL. A pronounced "break in slope" in the apatite age-elevation profile for results from most of NVL occurs at ∼ 50 Ma, approximating the start of uplift of the mountains. This marks the base of an uplifted apatite annealing zone. Prior to uplift, samples above this break lay within the apatite annealing zone whereas those samples below it had an apatite fission-track age of zero. For most of NVL, ∼ 5 km of uplift have been calculated. In the southeastern coastal region, however, uplift of the order of 10 km has been estimated, exposing apatite ages of only 25-35 Ma. Sphene and zircon ages from this area also appear reduced relative to the regional pattern, suggesting that the partial annealing zones for these minerals have been revealed. Confined track length distributions from the lower part of the apatite age profile indicate an initially rapid period of uplift (∼ 200-400 m Ma^-1) from ∼ 50 Ma. In the Lichen Hills-Outback Nunataks area, in the west of NVL, apatites have not been completely overprinted by the Jurassic thermal event associated with emplacement of the Ferrar Dolerite, and uplift here is of the order of only 4 km. Block faulting associated with uplift of the TAM is considered to be the same event as Rennick Faulting leading to the formation of the Rennick Graben.