Desarrollo de la Antártica

Takesi Nagata / THE ADVANCEMENT OF SCIENTlFIC RESEARCH '" extending in 45E ----. 900E in longítude and about 80 0 S in latitude, and Wilkes Land highland area {I20 0 ----. 150 0 E in long. and about 68°S in lat.) , all other higihlands have peak summits which are exposed above the ice sheet surface. As shown in Fig. 7, East Antarctica and West Antarctica are c1early separated by Trans-Antartic Mountains which extends over 3,5(}'0 !km from rhe nordhern end oí the west coast 'Of Ross Sea in Victoria Land to Coats Land in Weddell Sea. Geomorphologically speaking, East Antarctica forms a large platform above the sea level, whereas West Antarctica comprise a number of íslands and deep sea areas, sug¡gesting severe orogenic activities in the recent geologic history of this regíon. Geological and geomorphological researches of Antarctica could be classified inta two major item; nameIy a) bed-rock geology wihích deals with the geological histOTy of Antarctic bed-rock structure fram Precambrian to ICenozoic, and b) recent geological and geomor– phological !history of this continent mostly in Cenozoic, which is related to the development and diminution of Antarctic ice sheet. a) Geolor;y of Antarctic Bed-Rocks Since the time of the first returning of Antarctic rock pieces by Borchgrevink in 1894, geological researches of various localities in the Antarctic were continued until the IGY periodo Rock samples from "he exposedbed-rock areas on the Antarctic coast and the glacial moraines on the continental shelf were important samples for Ilhe Antarctic geological studies. A distinct geological difference between East and West Antarctica was pointed out by NordenskjOld in 1913. Up to the IGY time, geological researches were fairIy well made on the crystalline basement (gneisses, granites, etc.) and lBeacon sedimen. tary group of Victoria Land, Precambrian metamorphic rocks of East Antarctic coast, and Mesozoic·Cenozoic layers, volcanoes and volcanic rocks, granites, etc., of Antarctic Península ,and South Shetland Islands, and others. The results of these studies have Ied to the geologícal recognítion of East Antarctic shield and West Anta1'ctic Circum""'.Pacific arogenic zone. Systematíc geological surveys started at the occasion of IGY under an internationally coordinate program :llave resulted in a rapid progress in Antarctic geology. Fig. 8 summarizes an outline of the Antarctic geological structure rlhus revealed, where a definite dis– crepancy in geological structures between lEast and West Antarctica may be clearly observed. All basement rocks in East Antarctica are Precambrians, whose last solidification ages range from 4 x 10 8 to 95