The Present Day Geotectonic Setting of Antarctica

The Antarctic continent comprises three primary tectonic regions: (i) East Antarctica; (ii) West Antarctica and the associated West Antarctic Rift System (WARS); and (iii) the Transantarctic Mountains (Fig. 7.1).

East Antarctica is thought to feature Precambrian continental lithosphere c. 35-45 km thick (Bentley, 1991), stable, coherent and topographically high (Cogley, 1984), that held a central position in the Palaeozoic supercontinent of Gondwana (Tingley, 1991) as it did in the Mesoproterozoic supercontinent Rodinia (Dalziel, 1991; Moores, 1991).

In contrast, West Antarctica is an amalgamation of low-lying, 20-35 km thick, younger crustal blocks (Janowski and Drewry, 1981; Dalziel and Elliot, 1982). The West Antarctic Rift lithosphere compares to major Cenozoic continental rift systems (Behrendt, 1999). In the Ross Sea, the WARS borders the Transantarctic Mountains on their eastern side as a broad region of thinned continental crust associated with Cretaceous and episodic Cenozoic extension (Behrendt et al., 1991a,b; Behrendt, 1999). The WARS has high heat flow (83-126 mWm~2) (Blackman et al., 1987; Berg et al., 1989) and thick (5-14 km) sedimentary basins with recent faulting (Cande and Leslie, 1986; Cooper et al., 1987; Hamilton et al., 2001). The Ross Archipelago (LeMasurier and Thomson, 1990) is currently active with fumarolic activity associated with alkaline volcanism at Mt. Erebus and Mt. Melbourne. The crust in the WARS is currently ~19 + 2km thick (Trehu, 1989; Cooper et al., 1997).

The Transantarctic Mountains are approximately 2,500 km long and 200 km wide, dividing East Antarctica from West Antarctica with peaks that rise over 4 km above sea level. Crustal thickness estimates under the Transantarctic Mountains vary between 20 and 45 km (ten Brink et al., 1993, 1997; Cooper et al., 1997; Busetti et al., 1999; Kanao et al., 2002; Bannister et al., 2003). These mountains sharply differ from most mountain ranges of similar size and lateral extent because their formation did not reflect any compressional orogenic phases, but rather a process thought to have been

Figure 7.1: Map showing the main geographic subdivision of Antarctica in three domains which also correspond to distinct tectonic regions: West Antarctica, Transantarctic Mountains and East Antarctica. The location of the two active volcanoes in the Ross Sea area is also shown (ME: Mt. Erebus; MM: Mt. Melbourne). Antarctic bed topography is based on the BEDMAP dataset (Lythe et al., 2000).

Figure 7.1: Map showing the main geographic subdivision of Antarctica in three domains which also correspond to distinct tectonic regions: West Antarctica, Transantarctic Mountains and East Antarctica. The location of the two active volcanoes in the Ross Sea area is also shown (ME: Mt. Erebus; MM: Mt. Melbourne). Antarctic bed topography is based on the BEDMAP dataset (Lythe et al., 2000).

directly linked and causally related to the development of the WARS (e.g. ten Brink et al., 1997; Studinger et al., 2004, and references therein). The Transantarctic Mountains uplifted ~ 6-10 km in an asymmetric tilt block formation and underwent denudation from the Cenozoic to the Cretaceous (Fitzgerald, 1992, 1995; Studinger et al., 2004). The later part of the uplift and denudation phases occurred under persisting spreading/extension within the western Ross Sea (Cande et al., 2000) and has been concomitant with voluminous sediment infilling from the Late Eocene/Oligocene to present (Barrett et al., 2000, 2001; Hamilton et al., 2001).

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