Climate-driven changes in sedimentation rate influence phosphorus burial along continental margins of the northwestern Mediterranean

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Cortina, Aleix, Filippelli, Gabriel, Ochoa, Diana, Javier Sierro, Francisco, Flores, Jose-Abel, Grimalt, Joan O.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2018
• Subjects: biogeochemistry; biological production; burial (geology); climate variation; continental margin; Gulf of Lion; Gulf of lions; marine isotope stage; Mediterranean Sea; Mediterranean Sea (Northwest); MIS 8; oxygenation; paleoproductivity; Paleoredox; phosphorus; Phosphorus paleoproductivity; redox conditions; sediment-water interface; sedimentation rate; Termination IV; https://purl.org/pe-repo/ocde/ford#1.05.03; https://purl.org/pe-repo/ocde/ford#1.05.11; North Atlantic
• Online Access: https://hdl.handle.net/20.500.12866/4224; https://doi.org/10.1016/j.palaeo.2018.03.010

The burial of phosphorus (P) in continental margin sediments is a critical component of the marine reactive P budget, and thus an important factor in marine biological productivity. We determined downcore records of P from a site drilled on the upper slope of the Gulf of Lions (PRGL 1), northwestern Mediterranean Sea. Changes in total P content were monitored from Marine Isotope Stage (MIS) 6 to MIS 11. In addition, in two selected intervals (248-277 ka and 306-342 ka) the total P record was expanded by adding detailed geochemical analyses of the various P fractions, including oxyhydroxide-associated P, authigenic P, detrital P and organic P. Increased sedimentation rates during glacials owing to seaward migration of the Rhone's mouth, enhanced the burial of reactive P (oxyhydroxide-associated + authigenic + organic) phases by decreasing its time at the reactive sediment/water interface, in turn resulting in increasing proportion of authigenic to detrital phosphorus. The inverse was found for interglacial stages. The effects of glacial/interglacial variation in sedimentation rate over P geochemistry resulted in changes in sediment-water interface oxygenation, as well as in the efficiency of P burial, as shown by (C:P)(org) and C-org:P-react proxies respectively. Two events of high P deposition associated with authigenic (P-aut1) formation, at 335 (P-aut2) and 275 ka (P0052), were associated with periods of rapid disintegration of North Atlantic ice sheets leading to Ice Rafted Debris (IRD) deposition. These high P deposition events appear to be linked to short warm periods that followed cold episodes. Enhanced continental runoff owing to more humid conditions during short warm episodes could play a critical role for enhanced biogenic productivity and posterior authigenic P accumulation.