Gondwanaland and the evolution of the Indian Ocean

Abstract

In regions, such as the Indian Ocean, where geophysical data are largely lacking, reconstructions must be a compromise, allowing for the evolution of 'passive' margins and the inclusion of remanent continental blocks that are now isolated within the oceanic basins. Sea-floor spreading anomalies are re-examined in the context of the foregoing considerations, and emphasis is placed on the need to match anomalies that formed within the same transform segments. Despite subsequent attempts, it is considered that Norton and Sclater's (1979) configuration of Gondwanaland and its Mesozoic-Tertiary breakup only need small, but significant modifications. These allow for the inclusion of small, but critically located continental units between the major continental blocks. Only age differences are proposed for most of their anomaly 16 reconstruction, now largely corresponding to anomaly 20 times. No changes are proposed to Norton and Sclater's reconstruction for anomaly 34 times. Alterations to older reconstructions are mainly to allow for the inclusion of the Kerguelen, Gaussberg and Broken Ridges between India and Antarctica, and for the Agulhas-Falkland (Malvinas) Plateaux between Africa and Antarctica. The revised Gondwanaland reconstruction for early-middle Jurassic times appears to be more consistent with the geological and geophysical evidence, particularly reducing the need for differential motions of Sri Lanka and of the West Antarctic Peninsula. A review of the palaeomagnetic data indicates caution in the ability of extant data to distinguish between most reconstructions proposed during the last decade; considerable re-sampling and re-evaluation are required to adequately test between such Gondwanan models.

A psittacosaurid dinosaur from the Cretaceous of Thailand and its implications for the palaeogeographical history of Asia

“…The discovery of Psittacosaurus remains now shows that the Early Cretaceous terrestrial fauna of the Indochina block resembled that of other parts of mainland Asia, and these faunal resemblances definitely suggest geographical continuity. This contrasts with recent palaeogeographical reconstructions based mainly on palaeomagnetic data, such as that by Tarling (1988), which show 'Sundaland' (including the Indochina block) in rather uncertain positions in the proto-Indian ocean, between Australia and Asia, during the Cretaceous. In that case, palaeontological evidence constrains palaeogeographical reconstructions based on other lines of evidence.…”

New Developments in the Pre‐rift Prospectivity of the Eritrean Red Sea

“…The break-up of the Africa-Madagascar-India-Arabia fragments of Gondwana dominated the Mesozoic -Tertiary history of the region (Tarling, 1988). Consequently the rifts, which have evolved either into aulacogens (failed rifts) or passive margins fronting onto new oceans, form a related series of basins in this region.…”

The potential for Cretaceous coal in Antarctica

“…At the Jurassic/Cretaceous boundary (c. 140 Ma), the supercontinent was largely intact, but by Barremian times Africa and Arabia were starting to separate from West Gondwana as it rotated away anticlockwise. A scissorlike opening progressed into the South Atlantic; by the Late Cretaceous, the entire length of the South Atlantic was opening (Norton and Sclater, 1979;Tarling, 1988). India separated from Antarctica some time in the Early Cretaceous, and began to move northwards very rapidly.…”