High-resolution Deglacial to Holocene paleoceanographic records from the Sabrina Coast, East Antarctica: Preliminary foraminifer-based results from NBP14-02

Abstract:

Cruise 14-02 of the RV/IB N.B. Palmer conducted the first multidisciplinary oceanographic investigation of the continental shelf within the Dalton Iceberg Tongue polynya off the Sabrina Coast, East Antarctica. At >350 m in the northeastern polynya, hydrographic measurements confirmed that relatively warm (>0°C) oceanic thermocline water from near the shelf break has been imported to the shelf but likely within an interior recirculation associated with local mid-shelf bathymetry. CHIRP sub-bottom data revealed ~15 m of acoustically transparent sediment in a 550-m deep basin proximal to this feature. A suite of coring devices was used to recover a complete 13-m sequence of Late Pleistocene glacial diamict and Holocene laminated diatom oozes and muds (NBP14-02 MC 45, KC 27B, JPC 27, and JKC 53) with chronology constrained by ²¹⁰Pb and foraminifer-based AMS ¹⁴C dates.

Unlike many Antarctic margin sedimentary sequences, biogenic carbonate (CaCO₃) is exceptionally well preserved throughout the sedimentary sequence, likely due to non-corrosive bottom waters and/or low sedimentary organic carbon content. Planktic foraminifer Neogloboquadrina pachyderma(s) is present throughout and abundant in the diatomaceous muds. Bulimina aculeata, which prefers calm, hemipelagic environments and bottom water temperatures >0°C, dominates the living benthic foraminifer assemblage.

Fossil assemblages oscillate between B. aculeata and Trifarina angulosa-dominated assemblages. As T. angulosa is associated with oxygenated bottom waters and strong bottom currents, this assemblage may record past changes in the location of the Polar and Slope Fronts. This interpretation is supported by T. angulosa presence in Thalassiothrix diatom oozes, which are associated with oceanic frontal zones and rapid biosiliceous sedimentation. Preliminary foraminifer oxygen and carbon isotopes, N. pachyderma(s) presence, and the observed T. angulosa Mg/Ca‑temperature (-1.8 to 0°C) relationship highlight the potential for detailed regional foraminifer-based paleoceanographic records, which will provide critical tests for developing proxies, including TEX₈₆ paleothermometry. Future paleoceanographic studies will be supported by data from two long‑term oceanographic and sediment trap moorings deployed near the core site.