T03_P14

Palynological samples in marine cores: pollen extraction, dating, comparison with foraminiferal shells: a methodological challenge to investigate past reservoir ages

Tisnerat-laborde N¹, Coussin V², Thil F¹, Combrieu-Nebout N³, Fersi W², Eynaud F⁴, Toucanne S⁵, Babonneau N², Cattaneo A⁵, Penaud A²

¹LSCE/IPSL , Gif-sur-Yvette, France, ²LGO Univ Brest IUEM, Plouzané, France, ³HNHP/CNRS-MNHN-UPVD, Paris, France, ⁴EPOC-OASU, Univ.Bordeaux, Pessac, France, ⁵IFREMER, Geosciences Marines, Plouzané, France

The reconstruction of changes in marine reservoir age is a particularly challenging task but essential in paleo-oceanography to improve the chrono-stratigraphy of marine cores. In this work we have investigated the possibility of using continental material as monospecific pollen grains (Pinus) as well as palynological treatment residues (bulk or additionally treated with KOH to dissolve amorphous organic matter) and foraminifera collected in the same levels to study reservoir age variations over time (INSU EC2CO-LEFE project “DATAPOL”).

In a first step, we describe the methodology developed to extract pollen grains on cores MD04-2801 (Algerian Margin, Holocene) and MD13-3438 (northern Bay of Biscay, Heinrich Stadial 1) and the physico-chemical treatments of pollen carried out before ECHoMICADAS dating. The ¹⁴C results obtained between foraminifera, pollen, and palynological residues are here presented for the first time, highlighting a great variability of ages according to the nature of dated samples (organic matter vs. calcite). These first results raise questions about the effects reservoir ages of bottom water masses and potential diagenetic impacts on palynomorph membranes during organic matter fossilization. We also preliminary show that the use of palynological residues cannot be used to date marine cores. However, new methodological investigation is necessary to find solutions to sort pollen more efficiently to advance the ¹⁴C dating of monospecific pollen samples.