The Kerguelen Province revisited: Additional constraints on the early development of the southeast Indian Ocean

The Kerguelen Province, consisting of two oceanic plateaus (Kerguelen, Brok en Ridge) and three basins (Enderby, Labuan and Diamantina), covers a large area of ocean floor in the southeast Indian Ocean. As very few magnetic an omalies have been identified in this area and only a few basement ages from the Kerguelen Plateau are known, reconstruction models of the Kerguelen Pr ovince are not well constrained. In an effort to gain more understanding ab out the evolution of this area, we have used satellite gravity to identify additional fracture zones. As they are likely to be associated with high fr equency and low amplitude gravity anomalies, we have computed the vertical derivative map instead of the regular satellite gravity map. Using this app roach, we have identified a series of fracture zones in the Enderby Basin, which are aligned with the Mesozoic fracture zones in the Perth Basin and c onverge to the Kerguelen Fracture Zone. In the conjugate Bay of Bengal, we traced an equivalent pattern of fracture zones which, together, better cons train the early evolution of this part of the Indian Ocean. Synthesis of th ese images and the other available data from the Kerguelen Province, sugges ts that the spreading of India from both Australia and Antarctica is closel y related. Spreading between the three continents appears to have begun abo ut the same time, in the early Cretaceous and thus, the accretion of some p arts of the Kerguelen Province must have occurred before the onset of the q uiet magnetic period at 118 Ma. At about 96-99 Ma, when the spreading direc tion in the Indian Ocean had changed into a N-S direction, it also took pla ce throughout the Kerguelen Province. We find that previously proposed slow spreading in the Diamantina Zone and Labuan Basins, between 96-99 Ma and t he initiation of the Southeast Indian Ridge at 43 Ma, could not have taken place. Furthermore, we suggest that there is growing evidence that the same is true for spreading in the eastward continuation of the Diamantina Zone and Labuan Basin, between Australia and Antarctica. Initiation of spreading in this area is likely to be contemporaneous with the spreading in the Ker guelen Province and, thus, older than 96-99 Ma.