THE AMIRANTE RIDGE TROUGH COMPLEX - RESPONSE TO ROTATIONAL TRANSFORM RIFT DRIFT BETWEEN SEYCHELLES AND MADAGASCAR/

The Amirante ridge/trough complex developed along the Late Cretaceous transform boundary that separated the Seychelles/India and Madagascar/ Somali Basin plates. Motion between these plates was complex, comprisi ng sinistral N-S strike-slip movement coupled and coeval with counter- clockwise rotation induced when seafloor spreading developed in only t he southern portion of the transform. The overall morphology of the co mplex comprises a series of arcuate ridge and trough segments. These s egments were successively produced by tectonic and volcanic activity w ithin the zone of migrating plate contact adjacent to the rotational p ivot where compression was replaced by extension along the transform b oundary. In the extensional regime to the south of this contact zone t he Mascarene oceanic basin developed, whilst in the compressional zone further north island arcs developed and the ophiolites of Baluchistan were obducted from the Somali Basin onto the leading edge of the Seyc helles/India plate.