The geology of Antarctica

Over much of Antarctica rock exposures are very limited in extent, occurring mainly as isolated mountain ranges, nunataks, ice‐free fringing coastal areas, and offshore islands, but the geological record is rich and most revealing. The geological history of Antarctica has been a long and interesting one and in the course of geological time this continent has suffered the vicissitudes of mountain building processes, severe denudation and sedimentation in geosynclinal troughs, subsidence and incursions of the sea, large‐scale crumpling and fracturing of its sedimentary cover, and the inundation of vast areas by lava flows and showers of volcanic ashes. From an interpretation of the fossil fauna and flora it is clear that the climate of Antarctica has undergone several reversals. In Permo‐Carboniferous times glacial conditions prevailed, but in the Middle Jurassic the climate was temperate to sub‐tropical, supporting a luxuriant flora. Since that time the climate has slowly deteriorated to a final refrigeration in the Pleistocene and Recent. Even during the present glaciation there have been several phases of advance and retreat. Although the main continental shield of Antarctica is analogous to those of the other southern continents, comprising rocks which have undergone at least three phases of regional metamorphism, it is now clear that the continent is composed of two totally distinct and contrasting geological provinces, each of which has evolved separately under different environmental arid tectonic conditions since early Paleozoic times. East Antarctica, the older part of the continent, is the true Antarctic continental shield, on which rest relatively undisturbed early Paleozoic marine sediments and late Paleozoic‐early Mesozoic terrestrial sediments of the widespread southern Gondwana System. The latter succession is heavily intruded by thick, often differentiated, dolerite sheets of Lower Jurassic age. The main tectonic disturbances in East Antarctica appear to be block faulting of a late Tertiary‐Quaternary age, with which volcanism is widely associated. Many stratigraphic comparisons can be made with the other southern continents, especially southern Africa. West Antarctica, including the Antarctic Peninsula, is stratigraphically, structurally and technically closely akin to the west Patagonian Cordillera, and is indeed a southern extension of the Andean Mountain chain via the Scotia Arc. In comparison with East Antarctica it is much younger in age, having evolved mainly as a result of uparching of the Andean geosynclinal sediments in the late Paleozoic. Widespread lava and ash eruptions in the Upper Jurassic, marginal to the Andean geosyncline, were associated with a period of minor folding. This was followed by further sedimentation and the formation of the mid‐ to late Cretaceous Magellan geosyncline and the large‐scale intrusions of late Cretaceous‐early Tertiary times. Further sedimentation was abruptly terminated by mid‐Miocene volcanism which has continued intermittently until Recent times. Both block faulting and folding have played an important role in the formation of West Antarctica. On the basis of stratigraphical, petrological, structural and paleogeographical studies, it is evident that Antarctica comprises two main geological provinces, for which the names ‘Andean Province' (West Antarctica) and Gondwana Province' (East Antarctica) are proposed.

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