Evolution of the Southern Kerguelen Plateau deduced from seismic stratigraphic studies and Drilling at Sites 748 and 750

The evolution of the Raggatt Basin in the Southern Kerguelen Plateau, since the Late Cretaceous, was deduced from seismic stratigraphic interpretations of the multichannel seismic data and Ocean Drilling Program results at Sites 748 and 750. Synthetic seismograms were built using in situ and corrected core velocity values. Corrections were based on Wyllie's law, and exponential variations of porosity were calculated from logging data at Site 750. The synthetic seismograms in conjunction with the seismic sections allowed us to correlate the lithologic units and the seismic sequences. After the emplacement of oceanic basaltic basement at 110 Ma, the Late Cretaceous history of the Raggatt Basin was controlled by two rifting episodes at 88 Ma to the east and at 66 Ma to the west. The first rifting episode, with an axis of extension striking northwest-southeast, formed the eastern flank of the Southern Kerguelen Plateau. The second rifting episode, along a north-south axis, formed the 77°E Graben. At 45-42 Ma, the separation by seafloor spreading of the Kerguelen Plateau-Labuan Basin and Broken Ridge-Diamantina Zone marks a third rifting episode, which was recorded on the Southern Kerguelen Plateau by erosion.