Nature and Implications of Asymmetric Sea-Floor Spreading - 'Different Rates for Different Plates'.

摘要

Asymmetric sea-floor spreading has occurred south of Australia within narrow longitudinal zones of the Southeast Indian Ocean. The process of asymmetric spreading can be shown to be continuous at the scale of about 10 km or less in contrast to a process involving large, discrete jumps of the ridge-crest position. As there are no discontinuities in the total opening rates between the Australian and Antarctic plates, discontinuities in one-limb rates result when asymmetric and symmetric spreading occur in adjacent zones, and ridge-crest offsets (transform faults) are formed as a consequence. In this case, the length of the transform zone changes with time, and the ridge-fracture-zone system does not record the geometry of the initial rift. Other large areas of the world's ocean basins, in particular the northeast and southwest Pacific, have probably undergone similar phases of tectonic evolution.