Late Mesozoic-Cenozoic geology of the Ross Sector, Antarctica (extended abstract)

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Abstract
Knowledge of the late Mesozoic and Cenozoic geology of Antarctica is still in its infancy, compared with that of other continents. While Precambrian-jurassic rocks are relatively well exposed in the highlands of the continent, the Cretaceous and Cenozoic rocks (except for the Antarctic Peninsula and Marie Byrd Land) are found near or below sea level and are often obscured by sheet and shelf ice. Geophysical evidence indicates that there are probably extensive areas of Cretaceous and Cenozoic sediments in the continental shelves, particularly around the Weddell and Ross seas. The most extensive studies carried out so far have been in the Ross Sector, where analysis of exposures and core material has provided important insights into the structure and history of the Ross Sea continental shelf and the Transantarctic Mountains. Early studies provided detailed accounts of glacial sediments and erosional features of the Transantarctic Mountains, glaciomarine sediments and palaeontology of coastal areas and volcanic features of the offshore islands near McMurdo Sound. Bottom sampling of Holocene sediments of the Ross Sea was also carried out during the first decades of this century. Structural interpretations portrayed the Ross Sea as a graben or Senkungsfeld and the Transantarctic Mountains as a major horst feature. Nineteen fifty-five marked the beginning of 17 years of major reconnaissance in the Transantarctic Mountains, the Dry Valleys and the offshore islands. Geophysical traverses contributed to the first studies of the Ross Sea continental shelf. Studies of terrestrial glacial history were interpreted as showing that such history was multiphasal and confined to the Quaternary. K/Ar dating of volcanic rocks associated with terrestrial sediments later extended this to the Pliocene. Discoveries of early Tertiary erratics at Minna Bluff and of late Cretaceous microfossils in eastern Taylor Valley indicate the existence of an as-yet undiscovered Cretaceous-Palaeogene succession somewhere south of McMurdo Sound. The drilling programmes, begun in 1972, contributed a vast, but still insufficient, amount of additional information. As a result of 80 years of investigation we can now account for about 5% and 73% of Palaeogene and Neogene time respectively.