Latest Devonian (Strunian) Ostracoda from the Buttons Formation, Bonaparte Basin, northwestern Australia: Biostratigraphy, palaeoecology and palaeozoogeography

Abstract

Twenty-seven ostracod species are reviewed and referred to 22 benthic genera: Armenites, Bairdia (Bairdia), Bairdia (Rectobairdia), Baschkirina, Beyrichiopsis, Cavellina, Chamishaella, Coeloenellina, Cryptocyprois, Diphyochilina, Geisina, Indivisia, Katatona, Knoxites, Marginia, Notoscapha, Parabolbinella, Parabouchekius, Rhytiobeyrichia, Serenida, Shishaella, Sulcella and Urftella?. The fauna also includes the eridostracan Cryptophyllus. Species newly described are Beyrichiopsis? anogma, Beyrichiopsis teicherti and Serenida? alta; species newly recorded are Bairdia (Rectobairdia) aff. philippovae Egorov, 1953, Cryptocyprois sp. cf. C. subgibberosa Buschmina, 1977, Indivisia baschkirica Rozhdestvenskaya & Tschigova, 1972, Parabolbinella sp. A and Parabolbinella sp. B. Three biozones [Sulcella (Postsulcella) altifrons Zone, Diphyochilina tryphera Zone and Bairdia (Bairdia) ordensis Zone] are established and used for local correlation. Palaeoecologically, the ostracods are interpreted as indigenous, low energy thanatocoenoses, representing an Eifelian mega-assemblage, and are indicative of a shallow, generally well oxygenated lagoonal environment, below storm wave base. A gradual salinity increase is indicated by the appearance of stenohaline marine bairdioids in the upper part of the Buttons Formation. Long range correlation of this cosmopolitan ostracod fauna is with the late Famennian (Strunian, in particular). Strong zoogeographic links exist with the western margins of Palaeotethys (North Africa, Spain, France, Belgium, Poland), the East European Platform and Kazakhstan. Weaker links are with South China, northeast Russia (Omolon Massif) and the Cordilleran Province of North America. Benthic ostracods, lacking a pelagic larval stage, could not have crossed deep oceanic barriers. The observed zoogeographic links probably indicate that the shallow shelves of the western part of Gondwana and Laurentia-Baltica were close enough to permit genetic exchange and migration during transgressive pulses, along juxtaposed shallow shelves of the adjacent blocks of Gondwana and Laurentia-Baltica. A similar connection probably existed between the South China Plate and northwestern Australia, via terranes within the eastern end of the palaeotethyan equatorial belt.