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ABSTRACT: Plate Kinematics and Passive Margin Development in the Southern Indian Ocean

M. F. Coffin, J. -Y. Royer, S. C. Cande, R. Schlich, P. A. Symonds, J. G. Sclater, K. Kelts, S. W. Wise

The development of the Indian Ocean began in the Middle to Late Jurassic with the breakup of Gondwanaland. Marine magnetic anomalies and limited Deep Sea Drilling Project and Ocean Drilling Program core samples have been used to date the crust. Fracture zone trends interpreted from satellite (Seasat and Geosat) altimetry, and marine seismic, gravity, and magnetic data have been combined with crustal dates to produce kinematic models of plate movements. Between Jurassic and Late Cretaceous time the plate tectonic evolution of the Indian Ocean is poorly known. Mesozoic marine magnetic anomalies offshore eastern Africa, Antarctica, and Western Australia document plate motions during the interval; however, extensive areas of oceanic crust from which no anomalies have been ide tified and a dearth of fracture zones prevent detailed links with the much better defined plate kinematic synthesis of the past 80 m.y.

The passive margins of the southern Indian Ocean flank eastern Africa, Madagascar, Antarctica, and Australia. Simple and pure shear models have been proposed to account for these margins' development, but compelling evidence for a unique rifting mechanism has yet to be presented for any part of the margins. Each margin contains rifted and sheared sectors of markedly different structural style. Prerift sedimentary sections typically document a rift phase lasting several tens of millions of years before breakup occurred. Synrift sequences commonly contain evidence of volcanic activity. Variations in sediment supply and type, as well as variations in climate have resulted in widely differing postrift sedimentary sequences along the margins.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990