Geological mapping and analysis of granitoid basement rocks near the Carlyon Glacier and Brown Hills area to determine the tectonic environment during the Ross Orogeny

The Ross Orogeny refers to a sequence of geological events when East and West Antarctica met, resulting in subduction with associated deformation, crustal thickening, metamorphism and igneous activity. The rocks in South Victoria Land have a different character that is more compatible with crustal extension rather than subduction and continental convergence and were termed the Koettlitz Glacier Alkaline Province (KGAP). The nature and distribution of the KGAP was investigated south of the Skelton Glacier at Cheney Bluff, Fontain Bluff and in the Brown Hills area. Each area was geologically mapped and samples of granitoids were collected for geochemical and geochronological analysis. Near the Foggydog Glacier in the Brown Hills area, the basement granitoids, the overlying Beacon Supergroup sandstones and intrusive sills of the Ferrar group dolerties were mapped. Ferrar dolerties and underlying granitoids were collected from Bastion Hill. In all cases, observations were noted and sample localities were identified using available vertical and oblique aerial photographs and transferred to a contoured topographic database. Radiometric dating was conducted on samples. Mass spectrometric measurements were carried out to determine isotopic ratios required in the calculations of radiometric ages.