Jurassic and Early Cretaceous Ostracods from Western Australia: What They Reveal About Evolution of the Indian Ocean

Abstract

Using a combination of previous studies, some reinterpreted, and material from the Barremian of the Southern Carnarvon Platform and the middle–late Albian of the Exmouth Plateau, the distribution of ostracods from Jurassic and Early Cretaceous sediments of Western Australia is used for analyzing evolution of the Indian Ocean. The Early Jurassic ostracod fauna of Western Australia is Tethyan, similar to those from northwestern Europe. By Middle Jurassic it was still primarily Tethyan, with strong links to an East Tethys Province (northwest India, Madagascar, Tanzania, and northern Somalia) and weaker links with a South Tethys Province (Saudi Arabia, Egypt, Jordan, and Israel). Paradoxorhyncha accords with migration along the marine shelf of southern Gondwana between west-central Argentina and Western Australia. During the Late Jurassic to early Valanginian, the Western Australian ostracods belonged to a distinctive Indian Ocean ostracod fauna characterized by Gondwanan genera: Majungaella and Arculicythere. By late Valanginian–Hauterivian, this fauna had strong links with South Africa and southern South America reflecting breaching of physical barriers between the Indian Ocean and the Pacific. By the Barremian, occurrences of Rostrocytheridea in Western Australia, South Africa and Patagonia indicate inception of a new Austral Province. During the late Aptian–Albian, the ostracod fauna of Western Australia belonged to a discrete Austral Province (Madagascar, southern India, southern Argentina, the Falkland Plateau, Agulhas Bank, and South Africa) with species distributed parallel to a cool West Wind Drift current encircling Antarctica, Australia, and Papua New Guinea. Characteristic species include Arculicythere tumida Dingle, 1971, Isocythereis sealensis Dingle, 1971, and Cytherura? oertli Dingle, 1984.