Southernmost Kerguelen Plateau – Not a continental fragment

Abstract

Most models on the early continental drift of the Indian continent from Antarctica are guided by the existence of microcontinents that are supposed to be located beneath Elan Bank and the Southern Kerguelen Plateau in the Enderby Basin off East Antarctica. Two deep seismic lines were acquired to test these ideas by investigating the distribution of oceanic and continental crust in the Enderby Basin. In this contribution, we discuss the results of the eastern profile which images the crustal structure of the southernmost Kerguelen Plateau. The new deep seismic data show that the seismic velocity structure of the southernmost Kerguelen Plateau is different to that of extended continental crust but similar to other igneous oceanic plateaus worldwide. At the northern end of the profile, the Moho discontinuity lies at a depth below sea level of approximately 25 km. The position of the East Antarctic continent-ocean boundary is located close to its continental shelf edge. The maximum thickness of the East Antarctic transitional crust, at the southern termination of our line, is 22 km. Extrapolating our seismic reflection and refraction results show that the oceanic crust at 50° - 90°E in the Enderby Basin and Princess Elizabeth Trough formed whilst in receipt of excess melt from the Kerguelen plume around magnetic chron M4n causing a northward thickening of the oceanic crust since 130 Ma. These results strongly support a one-phase model for the drift of the Indian plate.