Establishing a robust sediment chronology in the Antarctic continental margin remains challenging because planktonic foraminifera, the primary material for accelerator mass spectrometry(AMS) 14C dating, are often absent, poorly preserved, or affected by old carbon. Previous studies have indirectly assigned interglacial sediments on the Bellingshausen Sea continental rise to Marine Isotope Stage (MIS) 5, largely based on tephra stratigraphy. However, recent AMS 14C dating from foraminifera and acid-insoluble organic matter (AIOM) in core BS17-GC02 indicates significantly younger ages, suggesting that the conventional tephra-based chronology requires reassessment. This study analyzes AMS 14C ages of planktonic foraminifera, magnetic susceptibility, CaCO3 concentration, color reflectance, and geochemical proxies from additional sediment cores (BS17-LC03 and BS17-GC04) collected from the Bellingshausen Sea continental margin to investigate these discrepancies. The results show that CaCO3 peaks and well-preserved foraminifera in the brownish interglacial layers yield calibrated AMS 14C ages of 32.9–39.1 ka. This conflicts with prior tephra chronology, which implied that deposition occurred during MIS 5, rather than suggesting that these distinctive intervals align with the later MIS 3 interglacial. Anomalously old tephra-derived ages may either result from sedimentary reworking or delayed tephra deposition. This research emphasizes the need for multi-proxy approaches and additional radiocarbon dating to obtain robust age control for Antarctic sedimentary records.
Ha et al. (Wed,) studied this question.