Late Mesozoic bivalve biostratigraphy of the Antarctic Peninsula region

Two groups of bivalves, the inoceramids and buchiids, are particularly useful zone fossils in the Mesozoic sedimentary formations of the Antarctic Peninsula region. In the Upper Jurassic, species of the generaRetroceramus,Malayomaorica,Buchia and Anopaeacan be traced considerable distances around the margins of Gondwana, and as such are especially valuable for regional correlations. Some of them, such as theR. haasti-subhaastigroup, can also be employed in detailed local correlations. In the Lower Cretaceous, the presence of cosmopolitanInoceramusspecies, such as members of theneocomiensis,concentricus and anglicusgroups, permits correlation with Northern Hemisphere faunas for the first time. Other stratigraphically important inoceramids are theI. ovatusgroup in the Lower Neocomian, theI. heteropterusgroup andAnopaea trapezoidalisin the Upper Neocomian andAn. cf.mandibulain the Albian. The only buchiids present in the Lower Cretaceous of Antarctica belong to the extensiveAucellina andina-radiatostriatagroup. Two types of Antarctic Upper Cretaceous inoceramids that are particularly important for regional correlations are the Upper CenomanianI. pictusgroup and the Turonian-ConiacianI. madagascariensis-ernstigroup. Senonian inoceramids are still poorly known but would seem to offer considerable scope for further studies.