Cenozoic Glaciation of Antarctica

The break-up of Gondwana during the Mesozoic Era altered the distribution of the continents in the southern hemisphere and exposed the East Antarctic craton to the southern ocean which still surrounds it. The tectonic processes that caused Gondwana to break up also affected East Antarctica by contributing to the uplift of the Transantarctic Mountains, by the formation of the West Antarctic rift system, and by rearranging the location of continental fragments (e.g., Marie Byrd Land, the Ellsworth Mountains, and the Antarctic Peninsula). 

The accumulation of snow and the growth of local ice caps in East Antarctica started during the Cenozoic Era after the Transantarctic Mountains had begun to rise at about 50 Ma (early Eocene). The uplift of the Transantarctic Mountains was related to the development of the West Antarctic rift valley which caused the eruption of alkaU-rich volcanic rocks (Chapter 16). In several cases, these rocks consist of subglacially erupted palagonites and hyaloclastites indicating that ice was present at the time of the eruption. The oldest subglaciaUy erupted volcanic rocks at Sheridan Bluff 

These proposals are not mutually exclusive because the ice sheet may have started both along the Transantarctic Mountains and in the Gamburtsev Mountains. In fact, the radio-echo surveys of Drewry (1971, 1972, 1973) indicate that an extensive network of subglacial valleys exists along the western flank of the Transantarctic Mountains as well as in the 

Gamburtsev Mountains in Fig. 17.3. Subglacial mountains in Queen MaudLandandNew Sch wabenland were also favorably positioned along the coast and may have developed centers of glaciation that contributed to the growth of the East Antarctic ice sheet. 

As time passed, the volume of the East Antarctic ice sheet increased sufficiently to bury the Transantarctic Mountains during the early Miocene until only the highest peaks remained ice-free as nunataks. At this time, the ice deeply eroded the valleys of the outlet glaciers and imposed on them the typical U-shaped cross-sections that are evident in the ice-free valleys of southern Victoria Land and elsewhere in the Transantarctic Mountains. More recently, the East Antarctic ice sheet thinned causing previously ice-covered areas of the Transantarctic Mountains to become ice-free and exposing till of the Sirius Group that was deposited by the ice sheet during its maximum extent. 

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