Distribution of ostracod and benthic foraminiferal assemblages during the last 550kyr in the East-Corsica basin, western Mediterranean Sea: A paleo-environmental reconstruction

Abstract

The study of Quaternary sediments covering the last 550 kyr from the borehole GDEC-4-2, East-Corsica basin, was performed through the study of benthic meiofaunal assemblages (ostracoda and benthic foraminifera) whose distribution responds to climate changes, and glacial-interglacial variability in particular. The interglacial ostracod group is mainly composed of the Argilloecia acuminata, Cytheropteron alatum, Henryhowella sp., Polycope sp. and Cytherella sp., which indicate an enhanced surface productivity and possibly high bottom water temperature during these warm intervals. Benthic foraminifera, such as Hoeglundina elegans, Sigmoilopsis schlumbergeri, Bigenerina nodosaria and Hyalinea balthica are predominant during interglacial periods and also show an increasing surface productivity associated to warm intervals. Increase in surface productivity would contribute to an enhanced export of organic matter to sea floor at the GDEC-4-2 site during interglacial periods. The bottom temperature drop coupled with the important sedimentary inputs (associated to a significant quantity of refractory organic matter) during glacial periods was highlighted by the predominance of ostracoda, such as Paradoxostoma sp., Cytheropteron testudo, Bathycythere vanstraateni, Macrocypris sp., Echinocythereis echinata and benthic foraminifera as Bolivina spathulata, Bulimina costata, and Bulimina marginata. The distribution of some benthic foraminifera species describing a turnover system allowed the characterization of the last three climate cycles (MIS 8-9, MIS 6-7, MIS 1-5) probably Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. marked by changes of bottom water paleoceanographic conditions in terms of temperature, salinity, bottom current intensity and surface productivity. The cyclic variations of the allochthonous group recorded over the last 550 kyr suggest a major role played by the eustatic factor, with the latter possibly favouring down slope transport. The distribution of this group allowed thus establishing a link between shelf-basin sediment transfer and climate, with enhanced shelf-basin sediment transfer during glacial low stands.

Effects of the Younger Dryas climate event recorded in sediment near the western Irish seaboard

“…More significantly, H. balthica first appears in VC9 a very short distance (10 cm) below the level of the 14 C date of 9264 AE 162 cal BP (Figure 2e, grey trend line). This particular interglacial benthic foraminiferal species is mainly a neritic to upper bathyal form (Rosenthal et al, 2011; see also Ross, 1984 andMinto'o, Bassetti, Toucanne, &Jouet, 2016 for discussion on its use as a palaeoclimatic indicator). This taxon is known to have first evolved in the early Pleistocene (e.g., Bayliss, 1969;Ross, 1984), or possibly even as early as the Pliocene (e.g., Hermelin, 1991); however, it has been noted as conspicuously absent before 10,000 BP in marine sediments recovered from the 1.…”