Large-scale rotational extension triggered basin formation in interior East Antarctica

Egidio Armadillo, Daniele Rizzello, Pietro Balbi, Alessandro Ghirotto, Davide Scafidi, Guy Paxman, Andrea Zunino, Fausto Ferraccioli, Laura Crispini, Andreas Läufer, Frank Lisker, Antonia Ruppel, Danilo Morelli, Martin Siegert

Recent sub-ice topography investigations have imaged with greatly improved detail a set of enigmatic low-elevation V-shaped basins hidden beneath a very large sector of the East Antarctic Ice Sheet. Here we show that these basins form a semi-continental sized fan shaped physiographic unit which radiates from a pin point near the South Pole and name it the East Antarctic Fan-shaped Basin Province. By jointly interpreting sub-ice topography and geophysical data, we demonstrate that the fan-like landscape originated from a distributed intraplate rotational extension before Gondwana breakup which had three continental-scale consequences. i) Laterally, to the west, it caused compression and the consequent uplift of the Gamburtsev Mountains. ii) To the east, the northernmost Transantarctic Mountains segment was rotated clockwise of ~20° overriding the West Antarctic Rift System’s hot lithosphere, causing segmentation of the mountain chain into three blocks and their differential uplift due to thermal buoyancy. iii) To the North, the transcurrent edge of the fan formed the lithospheric weakness that controlled the break-up of Gondwana by driving the propagation of Antarctica/Australia separation and shaping the resulting semi-circular passive continental margins. These processes have substantially influenced the present-day East Antarctica sub-ice landscape and the evolution of the overlying ice-sheet.