Scientific Results from the 2002-2003 Prince Charles Mountains Expedition of Germany and Australia (PCMEGA) - First part 

Preface

During the 2002-2003 Austral summer the PCMEGA expedition of twenty scientists from five Australian, one Russian and six German research institutions joined forces to undertake a comprehensive onshore geoscience project under the auspices of the Australian Antarctic Division (AAD) and the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR). This work involved a major airborne geophysical investigation into the subglacial structure of the southern Prince Charles Mountains and the geological architecture of the bedrock geology. The control that this geology has on shaping the geomorphic evolution of the region, together with a comprehensive sampling program to establish the age of the continent and its relationship to other continental fragments when they were assembled as part of the supercontinent Gondwana, approximately 500 million years ago.
The airborne geophysical program involved a Twin Otter fixed winged aircraft flying in a surveyed grid over an area of 81 000 square kilometres. The BGR supplied and operated an aircraft mounted ice-penetrating radar and the geophysical contractor, Fugro Airborne Surveys, carried out the airborne gravity and magnetic program. This produced over 30 000 kilometres of high-quality gravity, magnetic and ice depth data that has enabled the scientists to map the subglacial geology and topography at depths of up to 3.5 kilometres below the current ice surface. The survey has been able to locate and identify part of the Gamburtsev sub-glacial Mountains, a major glacial drainage divide and much speculated about region that lies beneath the East Antarctic ice sheet some 1000 kilometres inland from the continental margin.
As a major bonus to the geophysics program there was the acquisition of some additional 20 000 kilometres of geophysical data from the upper reaches of the Lambert and its tributary glaciers. This data was acquired during the Twin Otters daily flights over known areas of out cropping rock from Mount Cresswell, the main logistic and fuel base, and the survey area. The additional ice radar data and its precise GPS surveyed positions will provide important constraints on the volume of ice flowing through the Lambert-Amery ice drainage system and any mass-balance calculation of ice volumes. The additional gravity and magnetic data obtained during these flights is also critical as it can be directly correlated with the petro-physical properties of the exposed rocks visited by the geological field parties.
The geological team included fourteen geologists and three Field Training Officers. The team divided into parties of two or more individuals and visited the majority of the widely scattered nunataks. Twenty-four sites were investigated in detail, incorporating field camps at Mt Stinear, Cumpston Massif, Clemence Massif, Mt Dummit, Wilson Bluff, Rofe Glacier, Tingey Glacier, Mt Rubin, Mt Ruker, Rimmington Cirque and various light-weight camps along the Mawson Escarpment. Detailed observations and maps at 1:10 000-1:50 000 were made on bedrock outcrops and studies were made of early Cenozoic-Recent weathering, glacial, fluvial, biological and lacustrine landforms and sediments.
Field observations, and preliminary scientific results were presented and discussed during the 2003 9th ISAES in Potsdam, and the 2004 XXVII SCAR meeting in Bremen, Germany. The present issue contains the first part of the PCMEGA contributions and provides a summary of the geological setting and initial potential field data from the airborne geophysics program. The first paper by Lisker et al. reviews the setting of the Lambert Graben, its relationship to the southern Prince Charles Mountains and how thermochronological studies may impact on the understanding of the remarkably widespread peneplane that defines the summit of many of the mountains. This enigmatic flat plateau hints at the regions older history. The short notes and the maps by Phillips et al. attempts to correlate the geology and magnetic trends across of the Lambert Glacier and illustrates the distribution of lithologies and structures along the 120 km long Mawson Escarpment that forms the eastern boundary of the Lambert Glacier. The Corvino et al. paper presents new structural and SHRIMP U-Pb zircon age data from the Clemence Massif, a nunatak that lies to the north of the Mawson Escarpment. These results highlight disparities between the Neoproterozoic-Cambrian tectonic histories of the northern and central Prince Charles Mountains. The stratigraphic and structural paper of Phillips et al. is a synthesis of the features observed in the metasediments that are observed to the west of the Lambert Glacier. The two final papers describe the methodology employed for the data collection and reduction of the airborne magnetic (Damaske & McLean) and gravity surveys (McLean & Reitmayr) flown south of the Prince Charles Mountains. These papers present the new data sets and provide preliminary interpretations.

Norbert W. Roland
Bundesanstalt für Geowissenschaffen und Rohstoffe, Hannover (Germany)

Christopher J.L. Wilson
School of Earth Sciences, The University of Melbourne, Victoria (Australia)

December 2005