Structure and tectonic history of the southern Kerguelen Plateau (Indian Ocean) deduced from seismic reflection data

Early single-channel and recent multichannel seismic reflection data together reveal major tectonic events in the history of the Southern Kerguelen Plateau (SKP). The SKP was created by Early Cretaceous volcanism which was mainly subaerial. We estimate the age of the adjacent ocean basins to be similar to that of the plateau. Following termination of the main volcanism, the SKP began to subside and to accumulate sediment. A lower sedimentary megasequence was deposited at this time, primarily in depressions on the plateau. At about 88 Ma, tectonism affected the eastern Raggatt Basin; this tectonism may be related to faulting which created the steep eastern margin of the SKP. At about 72 Ma, predominant tectonic activity, characterized by widespread extension and uplift forming the tilted block morphology, occurred over large areas of the SKP. The extension centered along several NW-SE trending rift systems, in places creating well-preserved axial rifts. The largest structure of this kind, the Central SKP Uplift, lies along the center of the SKP; its relief increases from the southernmost part of the plateau toward the NW. The northernmost part of this uplift, the Banzare Bank, was elevated during rifting above sea level and was eroded. A second extensional structure, the SW Uplift, lies in the SW corner of the plateau, and other, smaller structures may also be present. The extension appears to have culminated in the initiation of the Southeast Indian Ridge at 43 Ma, but, at least in the Raggatt Basin, the two events were not continuous. Tectonic subsidence that was associated with the extension corresponds to deposition of a second megasequence, estimated to be about 1000 m thick on Banzare Bank. The subparallel trend of the rift systems on the SKP to the Southeast Indian Ridge and their timing suggest that the rearrangement of spreading in the South Indian Ocean at 43 Ma was not solely the result of the collision of India with Asia; it started earlier in association with other plate motions in the area