Late Mesozoic bivalve biostratigraphy of the Antarctic Peninsula region

Abstract

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 genera Retroceramus , Malayomaorica , Buchia and Anopaea can be traced considerable distances around the margins of Gondwana, and as such are especially valuable for regional correlations. Some of them, such as the R. haasti - subhaasti group, can also be employed in detailed local correlations. In the Lower Cretaceous, the presence of cosmopolitan Inoceramus species, such as members of the neocomiensis , concentricus and anglicus groups, permits correlation with Northern Hemisphere faunas for the first time. Other stratigraphically important inoceramids are the I. ovatus group in the Lower Neocomian, the I. heteropterus group and Anopaea trapezoidalis in the Upper Neocomian and An . cf. mandibula in the Albian. The only buchiids present in the Lower Cretaceous of Antarctica belong to the extensive Aucellina andina - radiatostriata group. Two types of Antarctic Upper Cretaceous inoceramids that are particularly important for regional correlations are the Upper Cenomanian I. pictus group and the Turonian-Coniacian I. madagascariensis - ernsti group. Senonian inoceramids are still poorly known but would seem to offer considerable scope for further studies.