Geophysical studies of the West Antarctic Rift System

Abstract

The West Antarctic rift system extends over a 3000 x 750 km, largely ice covered area from the Ross Sea to the base of the Antarctic Peninsula, comparable in area to the Basin and Range and the East African rift system. A spectacular rift shoulder scarp along which peaks reach 4-5 km maximum elevation marks one flank and extends from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. The rift shoulder has maximum present physiographic relief of 5 km in the Ross Embayment and 7 km in the Ellsworth Mountains-Byrd Subglacial Basin area. The Transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been interpreted as rising since about 60 Ma, at episodic rates of -• 1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100 m/m.y. The rift system is characterized by bimodal alkaline volcanic rocks ranging from at least Oligocene to the present. These are exposed asymmetrically along the rift flanks and at the south end of the Antarctic Peninsula. The trend of the Jurassic tholeiites (Ferrar dolerites, Kirkpatric basalts) marking the Jurassic Transantarctic rift is coincident with exposures of the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic rift shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed continuously (including the Dufek intrusion) along the lower-elevation (1-2 kin) section of Transantarctic Mountains to the Weddell Sea. Widely spaced aeromagnetic profiles in West Antarctica indicate the absence of Cenozoic volcanic rocks in the ice covered part of the Whitmore-Ellsworth-Mountain block and suggest their widespread occurrence beneath the western part of the ice sheet overlying the Byrd Subglacial Basin.

Inherited crustal features and tectonic blocks of the Transantarctic Mountains: An aeromagnetic perspective (Victoria Land, Antarctica)

“…Several geophysical investigations have been carried out in the Ross Sea area to study the crustal structure and tectonics of the West Antarctic rift system [Behrendt et al, 1993].…”

Animated tectonic reconstruction of the Southern Pacific and alkaline volcanism at its convergent margins since Eocene times

“…The Phoenix plate underwent subduction beneath the Antarctic Peninsula at its southeastern boundary, with which segments of the Antarctic-Phoenix ridge periodically collided leading to near-total destruction of the Phoenix plate (Larter and Barker, 1991). During much of Paleogene times, Antarctica underwent extension as the West Antarctic rift system slowly moved East Antarctica apart from West Antarctica, which we assume here included the Antarctic Peninsula (Behrendt et al, 1991;Cande et al, 2000). In addition to this, a complex of oceanic basins developed in the Scotia Sea at the region's eastern extremity, where west-directed subduction of the South American plate resulted in slow eastwards motion of an arc plate, as seen from Antarctica (Eagles et al, 2005).…”

Tectonic and denudational history of the Rennick Graben (North Victoria Land): Implications for the evolution of rifting between East and West Antarctica

“…[2] The boundary region between East and West Antarctica is formed by the Meso-Cenozoic West Antarctic rift system (WARS), one of the largest continental rifts on the Earth, extending for over 3000 km from the Ross Sea region (namely Victoria Land and Ross Sea) to the Weddel Sea margin [e.g., Behrendt et al, 1991;Tessensohn and Wörner, 1991] (Figure 1). The Transantarctic Mountains, a highelevation mountain chain extending for over 2500 km on the East Antarctic craton, terminate the West Antarctic rift system to the west [Fitzgerald et al, 1986;Tessensohn and Wörner, 1991].…”