40Ar-39Ar dating and isotopic composition of groundmass and felspar samples from core AND-2A

The AND-2A drillcore (Antarctic Drilling Program-ANDRILL) was successfully completed in late 2007 on the Antarctic continental margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar-39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar-39Ar ages, indicating that the AND-2A drillcore recovered <230 m of Middle Miocene (~128-358 m below sea floor, ~11.5-16.0 Ma) and >780 m of Early Miocene (~358-1093 m below sea floor, ~16.0-20.1 Ma). Results also highlight a nearly continuous stratigraphic record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ~19 cm/ka, possible oscillations of no more than a few hundreds of ka and a break within ~17.5-18.1 Ma. Comparison with available data from volcanic deposits on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the 'proto-Mount Morning' as the main source.

Chemical analysis of various geological samples from Northern Victoria Land, Antarctica

This paper reports the results of a preliminary palaeomagnetic investigation of the Admiralty Intrusives complex of northern Victoria Land, Antarctica. The samples were collected at Mt. Supernal and Inferno Peak, two pinions mainly formed of granodiorite and minor tonalite and emplaced at ab. 350 Ma at a high crustal level, as shown by amphibole geobarometric data and occurrence of miarolitic cavities. Microprobe and isothermal remanence analyses showed that magnetite. characterized by low coercivity and Curic point in the range 550-570 °C is the only primary ferromagnetic mineral. Stepwise thermaldemagnetization succeeded in isolatingamagnetization component. stable up to 530 °C. The virtual geomagnetic poles (VGPs) of the two plutons are different. That of Inferno Peak is consistent with the Australian palaeopoles of late Devonian-early Carboniferous age, whereas the location of the Mt. Supernal VGP probably results from the tectonic activity which affected the Ross Sea region during the Cenozoic.