East Antarctic craton

The East Antarctic Shield or Craton is a cratonic rock body that covers 10.2 million square kilometers or roughly 73% of the continent of Antarctica. The shield is almost entirely buried by the East Antarctic Ice Sheet that has an average thickness of 2200 meters but reaches up to 4700 meters in some locations. East Antarctica is separated from West Antarctica by the, 100–300 kilometer-wide, Transantarctic Mountains which span nearly 3,500 kilometers from the Weddell Sea to the Ross Sea. The East Antarctic Shield is then divided into an extensive central craton (Mawson craton) that occupies most of the continental interior and various other marginal cratons that are exposed along the coast.

Over the past 1 billion years, East Antarctica has traveled from tropical (to subtropical) southerly latitudes to its current location with the entire East Antarctic Shield positioned south of the Antarctic Circle. Despite its relative lack of motion over the past 75 million years, the East Antarctic Shield has played a significant role in the arrangement and motion of its surrounding plates during the amalgamation and separation of the supercontinents, Rodinia, Gondwana, and Pangea. Because the surface of the shield is covered by ice and thus, inaccessible by man, the information about its tectonic history comes primarily from seismic and core-sample data. Geologists have used this data to define the rock types present, age the rocks using radioactive dating techniques, unveil the climate history from isotope ratios, and trace the shield’s motion based on varying magnetic properties. Unfortunately, there are only a few places where data can be collected directly from the basement rock, and even at these locations, the exposed areas of the central craton can be misleading due to factors such as reworking during high-grade late Neoproterozoic to Cambrian deformation, variable overprinting by Cambrian tectonics, and the presence of younger metasediments. However, it has been determined that the East Antarctic Shield has a Precambrian to Ordovician basement of igneous and sedimentary rocks that are deformed and metamorphosed to varying degrees, and intruded by syn- to post-tectonic granites. The basement is locally overlain by undeformed Devonian to Jurassic sediments, and intruded by Jurassic tholeiitic plutonic and volcanic rocks. This knowledge of the shield’s structural features and compositions leads to the development of a tectonic history. The traditional models of East Antarctic Shield geology typically involve a three-stage tectonic history that includes:

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