Geochemical signatures of meltwater in mollusc shells from Antarctic coastal areas during the Holocene

• Main Author: Paul Arthur Berkman
• Format: Report
• Language: English
• Published: Byrd Polar Research Center, The Ohio State University 1994
• Subjects: crystrallography; fossils; oxygen isotopes; radiocarbon; raised beaches; trace metals; Antarctic; The Antarctic; Victoria Land; McMurdo Sound; Terra Nova Bay; Antarc*; Ice Sheet; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2258; http://id.nii.ac.jp/1291/00002258/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2258&item_no=1&attribute_id=18&file_no=1

Compositional, crystallographic and isotopic characteristics in calcitic shells of the scallop, Adamussium colbecki, were analyzed to interpret meltwater impacts in Antarctic coastal areas during the last 10000 years. Adjacent to glacial meltwater streams in West McMurdo Sound, live scallops had complementary trace element, unit cell volume and oxygen isotope profiles from 6 to 27m depth. Shell δ^<18>O_c (PDB) values, which were used to predict the δ^<18>O_w (SMOW) of the ambient seawater, produced estimates that accurately described the seawater isotopic composition and glacial meltwater volume in this coastal area. Radiocarbon reservoir corrections, based for the first time on Antarctic molluscs collected before 1945,were developed to constrain the Holocene chronologies of fossil Adamussium analogs. The similar 50‰ offset between the pre-nuclear and post-nuclear Δ^<14>C concentrations, in both Antarctic molluscs and seawater south of 60°S, indicates that a 1400±100 year reservoir correction is generally appropriate for Antarctic molluscs. Considering the temporal context of the shell δ^<18>O_c (PDB) values in Adamussium fossils from Terra Nova Bay, it is suggested that there was more meltwater along the Victoria Land Coast during the middle Holocene than at present. Together, these molluscan shell analyses provide a geochemical framework for assessing the responses of the Antarctic ice sheet margins to climate changes and their contribution to sea level during the Holocene.