An Airborne Gravity Survey South of the Prince Charles Mountains, East Antarctica
M. McLean1* & G. Reitmayr2
1School of Earth Sciences, The University of Melbourne, Melbourne 3001- Australia
2Bundesanstalt für Geowissenschaften und Rohstoffe, Postfach 510153, 30631 Hannover - Germany
Received 31 May 2005; accepted in revised form 18 November 2005
Abstract - The Lambert Glacier - Amery Ice Shelf in East Antarctica is a north-northeast trending graben, which is host to the largest glacier in the world. While the present configuration of this structure suggests a failed rift, some workers have suggested the Lambert region also preserves evidence of an earlier Cambrian suture between at least two Pre-Cambrian blocks that collided during the assembly of Gondwana.
Very little previous gravity data exists in the Prince Charles Mountains and no previous gravity data has been collected south of this region. A joint Australian / German expedition under the banner of PCMEGA (Prince Charles Mountains Expedition of Germany and Australia) was established to develop our understanding of this structure.
This paper presents the instrumentation, acquisition, processing and preliminary interpretations of the airborne gravity data acquired as part of the 2002/03 PCMEGA season. Line kilometres, flight line spacing and survey design details are outlined in Damaske and McLean (this volume). The gravity system consisted of a ZLS LaCoste & Romberg gravity meter mounted on a stabilised platform. Initial processing of the gravity data to the stage of free-air anomaly values was carried out by the equipment supplier. The details of further processing steps such as terrain and isostatic corrections are presented here.
The free-air gravity image is characterised by long wavelength anomalies which represent deep seated crustal structures. The extension of the Lambert rift has been imaged by in the free-air gravity and is interpreted to extend off to the southwest of the survey grid. A second sub-ice canyon has been interpreted to extend towards the southeast. These features are not nearly as dominant in the terrain corrected Bouguer image. This data is characterised by a regional north-south gradient interpreted to be variations in the crust/mantle discontinuity. The residual Bouguer image shows the gravity data which has been isostatically corrected. This data displays a long wavelength north east trending gravity high.
*Corresponding author (m.mclean@pgrad.unimelb.edu.au)