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Central Transantarctic Mountains (CTAM) Geophysics

The East Antarctic shield is one of Earth's oldest and largest cratonic assemblies, with a long-lived Archean to early Paleozoic history. Long-standing interest in the geologic evolution of this shield has been rekindled over the past decade by tectonic models linking East Antarctica with other Precambrian crustal elements in the Rodinia and Gondwanaland supercontinents. It is postulated that the Pacific margin of East Antarctica was rifted from Laurentia during late Neoproterozoic breakup of Rodinia, and it then developed as an active plate boundary during subsequent amalgamation of Gondwanaland in the earliest Paleozoic. If true, the East Antarctic shield played a key role in supercontinent transformation at a time of global changes in plate configuration, terrestrial surficial process, sea level, and marine geochemistry and biota. A better understanding of the geological evolution of the East Antarctic shield is therefore critical for studying Precambrian crustal evolution in general, as well as resource distribution, biosphere evolution, and glacial and climate history during later periods of Earth history. Because of nearly complete coverage by the polar ice cap, however, Antarctica remains the single most geologically unexplored continent. Exposures of cratonic basement are largely limited to coastal outcrops in George V Land and Terre Adélie (Australian sector), the Prince Charles Mountains and Enderby Land (Indian sector), and Queen Maud Land (African sector), where the geology is reasonably well-known. By contrast, little is known about the composition and structure of the shield interior. Given the extensive ice cover, collection of airborne geophysical data is the most cost-effective method to characterize broad areas of sub-ice basement and expand our knowledge of the East Antarctic shield interior.

Project Objectives

We will conduct an airborne magnetic survey (coupled with ground-based gravity measurements) across an important window into the East Antarctic shield where it is exposed in the Nimrod Glacier area of the central Transantarctic Mountains, in order to:

characterize the magnetic and gravity signature of East Antarctic crustal basement exposed at the Ross margin (Nimrod Group),
extend the magnetic data westward along a corridor across the polar ice cap in order to image the crust in icecovered areas,
obtain magnetic data over the Ross Orogen in order to image the ice-covered boundary between basement and supracrustal rocks, allowing us to better constrain the geometry of fundamental Ross structures, and
use the shape, trends, wavelengths, and amplitudes of magnetic anomalies to define magnetic domains in the shield, common building blocks for continent-scale studies of Precambrian geologic structure and evolution.

Relevance & Impact

This project will enhance the education of students, the advancement of under-represented groups, the research instrumentation of the U.S. Antarctic Program, partnerships between the federal government and institutions of higher education, and cooperation between national research programs. It will benefit society through basic research, which in turn may help with applied research in resource evaluation and the glacial history of Antarctica.

Project Chief:

Carol Finn
Box 25046 Denver Federal Center MS 964
Denver, CO 80225-0046

Phone: (303) 236-1345
Email: cfinn

Product

Anderson, E.D., Finn, C.A., Damaske, D., Abraham, J.D., Goldmann, F., Goodge, J.W., and Braddock, P., 2006, Aeromagnetic and Gravity Data Over the Central Transantarctic Mountains (CTAM), Antarctica: A Website for the Distribution of Data and Maps: U.S. Geological Survey Open-File Report 2006-1255, 17 p.

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