Age and palaeoenvironment of pliocene sediments, Cameron Inlet Formation, Eastern Flinders Island, Tasmania: implications for southeastern Australian biostratigraphy

A previously unrecorded thin unit of very Early Pliocene calcareous sediments of the Cameron Inlet Formation from two auger holes in central Flinders Island, Tasmania, has yielded a very diverse fauna of benthic Foraminifera and enough planktonic forms to allow fine correlation with international biostratigraphic standards (N19, approximately 5.3–4.4 Ma, or Lower Opoitian in New Zealand terminology). Ostracods are also recorded. It is older than an earlier recorded sample from North Patriarch Drain a few kilometres away. It lies within the Kalimnan of southeastern Australian stage nomenclature and probably equivalent to 1985 Molluscan Assemblage XVI. The sediments and faunas accumulated in very shallow, fully marine conditions, initially with some possible estuarine aspect that faded with time. The fauna is of well-known species, dominated by Parredicta kalimnensis (Parr, 1939). Other abundant and diverse forms are elphidiids and cibicidids. Agglutinated forms are almost absent and miliolids are diverse but minor components. The fauna includes a new polymorphinid genus and species that will be described elsewhere. The samples contain a bewildering array of unilocular forms. Water temperature appears to have been about 12°C. The Kalimnan Stage may encompass the entire Pliocene and two substages may be identifiable.