Palaeoceanographic and palaeoclimatic changes during the last 37,000 years detected in the SE Bay of Biscay based on benthic foraminifera

Abstract

Benthic foraminifera assemblages from a sedimentary core (PP10-12; 701 mwd) from the SE Bay of Biscay allow us to trace palaeoceanographic and palaeoclimatic changes occurred in this region during mid MIS 3 (Marine Isotope Stage 3) and MIS 1 interval (37–2.4 ka BP). Results are based on 176 benthic foraminifera species considering their ecology, the difference between autochthonous/allochthonous, preservation and oxygen rates, thus evidencing climatic and oceanographic events. MIS 3 is characterised by waters with a dominance of Cassidulina laevigata and Uvigerina peregrina. By the end of this interval, waters became colder and less oxygenated indicated by the occurrence of Melonis affinis. These conditions persisted at the beginning of MIS 2. The Heinrich Event 1 (H1) is well registered in this core with three intervals (H1a, H1s.s., H1b) where Hyalinea balthica dominates. During H1s.s. the coldest waters are registered, and the environment was unstable. These conditions continued during H1b when the occurrence of Globobulimina affinis evidences some intervals with anoxia. During Bølling-Allerød (B/A) waters were warmer and low-ventilated indicated by Bulimina gibba. Cassidulina laevigata dominates the Younger Dryas (YD) and the beginning of Lower Holocene, evidencing the occurrence of cool waters with low-oxygen and high organic matter content. The Lower to Middle Holocene transition is registered as a cold interval: Holocene Cooling Event (HCE-5). From the Middle Holocene onward water temperature were milder based on the dominance of Uvigerina peregrina.