Environmental changes in the Fleuve Manche paleoriver drainage system (Western Europe) linked to North Atlantic sub-millennial climate variability across Heinrich Stadial 1: Palynological evidence from the Bay of Biscay

Penaud, Aurélie; Fersi, Wiem; Toucanne, Samuel; Goñi, Maria Fernanda Sánchez; Rossignol, Linda; Naughton, Filipa; Wary, Mélanie; Eynaud, Frédérique

http://hdl.handle.net/10400.1/26270

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Authors

Penaud, Aurélie

Fersi, Wiem

Toucanne, Samuel

Goñi, Maria Fernanda Sánchez

Abstract(s)

Marine microfossils (dinoflagellate cysts and planktonic foraminifera) and geochemical (XRF-Ti/Ca)-based matic records from a core (MD13-3438) located off the Fleuve Manche (FM) paleo-mouth have revealed sustained warm summer sea surface temperatures (SSTs) during sub-millennial climate changes within (similar to 18-14.7 ka) may have played a key role in the FM regime related to the European Ice Sheet (EIS) melting In this study, we have analyzed the MD13-3438 pollen content over the HS1 at a mean resolution of similar to 50 years test whether vegetation-based air temperatures were coupled to SSTs face to this rapid climate variability. our results highlight two major phases of pollen sources at site MD13-3438, preventing the pollen record interpreted as a continuous record of the evolution of vegetation and climate occupying a single watershed HS1. The first phase, i.e. the HS1-a interval (similar to 18-16.8 ka), is marked by strong occurrences of boreal pollen (especially Picea-Abies). Considering their spatial distribution and the coalescence of the British and Scandinavian ice sheets into the North Sea during the Last Glacial Maximum, these taxa probably originated from North European Plain, i.e., eastern FM tributaries (east of the Rhine River), where cool-humid conditions generally prevailed. Then, the second phase, i.e. the HS1-b interval (similar to 16.8-14.7 ka BP), is characterized deceleration of the EIS retreat and the drop of boreal pollen values at site MD13-3438 further signing influence of the upstream FM drainage system and thus a better characterization of pollen sources related western FM tributaries. Superimposed to these two HS1 main phases, pollen fluctuations are concomitant sub-millennial variability in the EIS deglaciation intensity. During the early HS1 (HS1-a), we discuss two short-term increases in the ratio between deciduous trees (Quercus-Corylus-Alnus) and herbaceous plants (Plantago-Amaranthaceae-Artemisia). These events are coeval with phases of increasing dinocyst-based SST seasonality through summer SST amplification). We associate these events with lower contribution of the upstream catchment as well as, possibly, atmospheric warming and regional sea-level positive oscillations. The HS1-b composed of three main phases that appear more influenced by the downstream FM drainage system. HS1-b1 (16.8-16.3 ka BP) corresponds to the driest and coldest conditions west of the Rhine River. HS1-b2 (16.3-15.5 ka BP) is coeval with large arrivals of iceberg from the Hudson strait in the Bay of Biscay and likely to a major sea-level positive oscillation associated with a phase of FM valley reworking. HS1-b3 (15.5-14.7 ka BP) corresponds to persistent arid conditions that preceded the subsequent more humid tions recorded from 14.7 ka BP at the start of the Bolling-Allerod.