Reworked late Neogene Austrochlamys anderssoni (Mollusca: Bivalvia) from northern James Ross Island, Antarctica

• Published in: Antarctic Science
• Main Authors: Pirrie, D., Jonkers, H.A., Smellie, John L., Crame, J. Alistair, McArthur, J.M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2011
• Subjects: Glaciology; Ecology and Environment; Earth Sciences; Antarctic; Antarctic Peninsula; Cockburn; Cockburn Island; Hobbs; Ross Island; Antarc*; Antarctic Science; Antarctica; James Ross Island; permafrost
• Online Access: http://nora.nerc.ac.uk/id/eprint/14060/; https://nora.nerc.ac.uk/id/eprint/14060/1/-ANS-ANS23_02-S0954102010000842a.pdf; http://journals.cambridge.org/download.php?file=%2FANS%2FANS23_02%2FS0954102010000842a.pdf&code=2288f0d4172c6114a52396b9fb4b0cce

We report on the discovery of a new outcrop of fossiliferous Neogene sediments on northern James Ross Island, northern Antarctic Peninsula. Approximately 100 specimens of the pectinid bivalve Austrochlamys anderssoni (Hennig, 1911) were collected from the permafrost active layer. This bivalve species has a late Miocene to late Pliocene range and has previously been reported from both the glaciomarine Hobbs Glacier Formation and the interglacial Cockburn Island Formation in the James Ross Island area. The localized presence of abundant A. anderssoni within the permafrost suggests that the fossils have been frost heaved from an outcrop of either the Cockburn Island or the Hobbs Glacier formations, originally deposited on northern James Ross Island. The overall shell form, general absence of associated Antarctic Peninsula-derived clasts in the host sediment, and the measured Sr-87/(86) Sr isotope ratio of the shells (0.709050) which is indistinguishable from that for pectinid bivalves from the Cockburn Island Formation on Cockburn Island (0.709047) suggest that the shells were derived from a unit similar in age to the Cockburn Island Formation. This suggests that the Cockburn Island Formation was originally more laterally extensive than was previously known.