Biogenic carbonate fluxes and preservation in the northwestern Labrador Sea since the Last Glacial Maximum

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Marshall, Nicole R., de Vernal, Anne, Mucci, Alfonso, Filippova, Alexandra, Kienast, Markus, Gibb, Olivia, Hillaire-Marcel, Claude
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Labrador Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/53737/; https://oceanrep.geomar.de/id/eprint/53737/1/Marshalletal2021.pdf; https://oceanrep.geomar.de/id/eprint/53737/2/Marshalletal_SupplementaryData.docx; https://doi.org/10.1016/j.palaeo.2021.110498

Highlights • Porewater calcite dissolution may have occurred during the deglacial interval. • There is a significant decoupling of coccolith and alkenone concentrations in core 004. • Non-calcifying haptophytes most likely produced the alkenones in the glacial interval. Abstract The important changes that took place in the glacial cycle at the termination, from the Last Glacial Maximum to the present interglacial, deserve an examination of ocean sedimentary records that document past productivity, carbon fluxes, and carbonate preservation. In this study, we analyzed coccoliths, alkenones, and foraminifers in core HU2008–029-004 PC (61.46°N and 58.04°W, water depth = 2,674 m) from the northwestern Labrador Sea to document linkages between hydrographic conditions, biogenic carbonate fluxes to the seafloor, and their preservation/dissolution during the last 25,000 years. Large changes in coccolith and foraminifer concentrations are recorded, with sediments from the last glacial interval containing significantly less carbonate microfossils (9.5 ± 3.9 × 105 coccoliths g−1 and 2,860 ± 580 planktonic foraminifers g−1) than sediments from the deglacial and postglacial intervals (up to 3.1 × 108 coccoliths g−1 and 2.9 × 104 foraminifers g−1). Three foraminifer-based calcite dissolution indices were used to evaluate biogenic carbonate preservation: the planktonic foraminifer fragmentation index, the ratio of benthic-to-planktonic foraminifers (B/P), and the ratio of organic linings to benthic foraminifers (OL/B). Fragmentation remained low throughout the postglacial (mean of 4%) but reached up to 8% in the deglacial and peaked at 16% in samples from the Bølling-Allerød of the late glacial interval. Samples from the Bølling-Allerød and the deglacial interval also display a slightly elevated B/P index (>0.15), which suggests that some dissolution may have occurred. In contrast, with the exception of the Bølling-Allerød and the deglacial interval, near zero OL/B values characterize most of the sequence, suggesting good ...