Mid Twentieth Century Advances 19561972

IGY saw the establishment of a network of permanent bases around the continent from which to execute ship-based surveys of the margin, along with stations in the interior (Byrd, South Pole, Charcot and Vostok), enabling the first great scientific over-snow traverses gathering geophysical and glaciological data across the continent (Fogg, 1992, pp. 168-176). The technical and scientific success of IGY led an agreement to extend the research that had been initiated and the establishment of a Special (later Scientific) Committee on Antarctic Research (SCAR) in 1958 to facilitate and help coordinate these activities. The success of IGY also led participating nations in the years immediately following to craft an Antarctic Treaty, which was ratified in 1961 (Beeby, 1972).

Though geology was subordinate to the main mission of IGY, geologists enthusiastically took advantage of the extensive access to the continent made possible by their geophysical and glaciological colleagues. Geological surveys by contrast were carried out by smaller parties visiting the numerous but limited exposed patches of rock around the continent. By this time, there had been significant advances in the Earth sciences since the Heroic Era, and the application of this new knowledge to the Earth's only polar continent led to great interest in reports from the region. These advances included a robust geological time scale through radio-isotopic dating (Holmes, 1965), and the different character of the crust beneath oceans and continents recognized from seismology, along with the concept of continental drift from geology (Du Toit, 1937; Carey, 1958), later embodied in the theories of Sea Floor Spreading and Plate Tectonics (Dietz, 1961; Hess, 1962; Wilson, 1965).

By 1970, the comprehensive surveys carried out in the IGY and the decade following had resulted in a comprehensive new view of the climate, physiography, glaciology, geology and biota of the Antarctic continent, summarized in the American Geographical Society's map folio series (Bushnell, 1964-1975). Antarctic sedimentary strata overlying basement rocks were found to record a climate history similar to that of the other Gondwana continents, with dry warm conditions in Devonian times (390-340 Ma), ice-sheet glaciation in Carboniferous-early Permian times (340-280 Ma) and a humid temperate climate in Permian-Triassic times (280-200 Ma) with evidence of rivers, lakes and coal swamps. However, this long sedimentary record of deposition ended around 180 Ma ago with Jurassic igneous activity associated with the break-up of the Gondwana supercontinent, leaving a huge gap in the Antarctic geological record until the deposition of moraines around the Antarctic margin, then presumed to have formed from ice sheets in the Quaternary Period (Harrington, 1965).

Early post-IGY surveys of glacial deposits in the McMurdo Sound region by Pewe (1960), Bull et al. (1962), Nichols (1964) and others described the features they found in terms of four glacial episodes within the Quaternary Period, perhaps influenced by the prevailing view prior to the IGY in the Northern Hemisphere (Flint, 1957) and a lack of suitable fossil material or radiometric techniques for a sound chronology. Indeed, Nichols (1964) in his review of the status of Antarctic glacial geology stated, ''This writer believes that as yet there is no good evidence for Tertiary Antarctic glaciation''.

In the years that followed, K-Ar dating revealed a significant pre-Quaternary history for Antarctic Cenozoic ice sheets. In the Jones Mountains in West Antarctica, a glaciated surface overlain by basalt was dated at more than 10 Ma (Craddock et al., 1964) and in Taylor Valley west of McMurdo Sound, small basaltic cones overlain and underlain by evidence of glaciation yielded ages ranging between 2.8 and 3.6 Ma (Armstrong et al., 1968; Denton et al., 1970). Post-IGY research world-wide was reporting evidence of pre-Quaternary glaciers in the Arctic and of late Cenozoic cooling from fossil molluscs and plants in lower latitudes, leading Flint (1971, p. 441) to conclude, ''Glaciation occurred in the Miocene and Pliocene as well as in the Quaternary. Cold periods were more numerous than the four periods of the classical literature''. Cores from the floor of the Southern Ocean suggested that Antarctic ice could have been much older, with ice-rafted sand grains as old as Oligocene (Margolis and Kennett, 1970). But there was no way of showing whether these came from local ice caps or continental ice sheets.

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