Gravity modelling across the Transantarctic Mountains, Northern Victoria Land

Abstract

During GANOVEX V and GANOVEX VI, new gravity data were collected in northern Victoria Land. The GANOVEX V data cover the Mt. Melbourne 1:250.000 quadrangle, while the GANOVEX VI data Transantarctic Mountains south of the Drygalski Ice Tongue. The two data sets are connected by a coastal traverse. The measurements were constrained by satellite-positioned elevation (GPS) data and, in some cases, ice depth radar echo-sounding. Complete Bouguer corrections have been attempted to compensate for the effects of rugged terrain and surrounding ice. In the Mt. Melbourne quadrangle the regional gravity gradient is uniform, decreasing inland by 2.0 mgal/km. South of the Drygalski Ice Tongue the regional gradient is 3.0 mgal/km but becomes flat and variable inland over Beacon Supergroup rocks. Both profiles are consistent with a flexural uplift crustal model. A coast-parallel gravity profile reveals a long-wavelength anomaly of approximately 100 mgal amplitude, which is likely caused by a deep seated source. Gravity models suggest that crustal thickening on the order of 5.0 km to 5.5 km at the coastline between Terra Nova Bay and the region south of the ice tongue could account for the coastal anomaly. The increase in thickness might lie across two "domains" of different uplift, or perhaps in some way be related to a structure dating from the time of the Gondwana breakup.