Seafloor spreading magnetic anomalies in the Enderby Basin, East Antarctica

The timing of the early separation of India from the contiguous Antarctica- Australia is still an unresolved problem although it is well established th at Antarctica and India formed a single Indo-Antarctic platform prior to th e fragmentation of eastern Gondwanaland. Inadequate age information either in the form of magnetic anomaly isochrons or dating of oceanic rocks from t he conjugate margins of Antarctica and India perhaps led several authors to propose incomplete plate reconstruction models particularly for the early separation of India from Antarctica. Analysis of magnetic and satellite-der ived gravity data in the Enderby Basin, East Antarctica, reveals the presen ce of seafloor spreading type linear magnetic anomalies and eight new fract ure zones. The observed magnetic anomalies can be interpreted as the younge r sequence of Mesozoic anomalies M11-M0. Half-spreading rates range from 6. 5 to 2.8 cm/yr and are comparable with those measured in the Bay of Bengal. These similarities in the Mesozoic magnetic anomaly sequence and in the sp reading rates provide evidence that these two basins are conjugate and cont emporary. A consistent plate reconstruction model can be derived from the i dentified conjugate patterns of Mesozoic magnetic anomalies and fracture zo nes. The occurrence of the oldest magnetic anomaly M11 close to the coasts in these two offshore basins unequivocally suggests that the break-up of In dia from Antarctica occurred before similar to 134 Ma. (C) 2001 Elsevier Sc ience B.V, All rights reserved.