Site U1624 - IODP Publications

As the main gateway to the Arctic Ocean, the Fram Strait (FS) plays a critical role in regulating central Arctic– Atlantic water exchange and global climate dynamics. Paleoclimate reconstructions from this key region remain particularly challenging due to the scarcity of continuous, well-positioned and high-resolution sedimentary records. During International Ocean Discovery Program (IODP) Expedition 403 (Eastern Fram Strait Paleo-Archive), Sites U1621 and U1623 were cored in the Bellsund Drift, southeastern Fram Strait. This study presents detailed calcareous nannofossil data from Holes U1621A and U1623A, documenting an unprecedented record of key Quaternary calcifying phytoplankton groups in the region. Intercalibrated with shipboard magnetostratigraphic data, these records establish the first chronological framework for the Bellsund Drift sediments, spanning the last ~1 million years. Increases in nannofossil abundances—defined as Nannofossil Abundance (NA) events—are identified at both sites and closely correlate with peak enhancements in Ca/Ti and Sr/Ti ratios recorded in X-ray fluorescence (XRF) data. This biogenic-geochemical covariance provides compelling evidence of fluctuations in primary productivity and sedimentary calcium carbonate (CaCO3) concentration, linked to