Palaeontology and Palaeoenvironment of the Marine Plain area (Vestfold Hills) in the Pliocene

Brief description

This project is very closely related to ASAC project 666 (ASAC_666). See that project for more details. A copy of the masters thesis arising from the project is attached to the record. Physical samples are stored at the University of Melbourne. Taken from the abstract of the attached thesis: Marine Plain covers an area of approximately 10 square kilometres, and is located 10 km southeast of Davis Station near the Vestfold Hills, East Antarctica. The sediments at Marine Plain are significantly older than other strata in the Vestfold Hills and unconformably overlie Precambrian gneiss. This thesis describes nine species of gastropods from five families and ten bivalves from eight families. Included within this study are descriptions of two new species of bivalve and one new bivalve genus; Ennucula sp. nov., Hiatellidae gen. nov. sp. nov. The gastropods include Parmophoridea cf. melvilli, Falsimargarita sp., Naticidae genus and species indeterminate A and Naticidae genus and species indeterminate B, Prolacuna sp., Taniella ? sp., Euspira sp., Chlanidota (Chlanidota) signeyana, and Trophon sp. Bivalves include Ennucula sp. nov., Neilo sp., Limopsis sp., LIssarca sp., "Chlamys" tuftensis, Austrochlamys anderssoni, Limatula (Antarctolima) cf. hodgsoni, Cyclocardia cf. asartoides, Hiatellidae gen. nov. sp. nov., and the Holocene aged Laternula elliptica. The molluscan assemblages at Marine Plain are found in two distinct horizons within the Sorsdal Formation. The only species common to both units is the bivalve "Chlamys" tuftensis. The Early Pliocene age of the sediments at Marine Plain is based on the presence "Chlamys" tuftensis in the sediments and diatom biostratigraphy. The highly lithified upper band of the Sorsdal Formation, the Graveyard Sandstone Member, is 30-50 centimetres thick. The fauna in the Graveyard Sandstsone Member is better preserved than that in the lower diamictite unit, with better shell preservation and larger numbers of articulated valves. Bivalves from five genera make up the total macrofossils present in the unit. The lower unit is diatomaceous sandstone, 1.4 metres thick. This unit has a high diversity of macrofossils, including archaeogastropods (and burrowing trails), echinoids, serpulid worms, algae and bryozoa (both sheet and stick). The Pliocene aged sediments at Marine Plain were deposited in a soft bottom, shallow marine environment. The ice cover in Antarctica was probably significantly reduced compared to present and the sea water temperature was possibly warmer. The molluscs however offer little evidence of this. The molluscs are a combination of both epifaunal and infaunal forms with varied modes of feeding including suspension and filter feeders and some gastropod carnivores. To date Marine Plain has yielded the best preserved and most diverse, available Pliocene fossils in Antarctica. Present day shelly marine communities in the vicinity of Davis station mainly consist of one species of Laternula, echinoids and pectinids, with ice rafted diatoms. The analysis of the Pliocene invertebrate fauna at Marine Plain provides a rare insight into the evolution of modern Antarctic marine communities and the Pliocene global warming debate. However, limited outcrop exposure, poor preservation and often severe distortion due to compaction hamper the utility of the macrofossils at Marine Plain.