Filling the Gap of the Late Quaternary Planktonic Foraminifera Record in the Western Mediterranean: Paleoceanographic Changes in the Ligurian Sea Over the Last 27.4 Ka

Abstract

This study aims to expand our understanding of the paleoceanographic changes in the western Mediterranean during the Late Quaternary by investigating the planktonic foraminifera and the reworked coccolith records of the NDT_22_2016 core (27.4 ka cal BP to present) in the Ligurian Sea. To achieve this a robust age model was developed using 17 radiocarbon dating, allowing sub-millennial resolution analyses. The last glacial period was characterized by cold-eutrophic species (Globigerinita glutinata, Globigerina bulloides and Turborotalita quinqueloba), while formation of a seasonal deep chlorophyll maximum (DCM) was confined to the south-western Mediterranean as testified by the distribution of Neogloboquadrina incompta. The intervening Heinrich events were identified in the Ligurian Sea through reworked coccolith peaks and the subsequent increase of N. incompta, indicating enhanced runoff and DCM formation, respectively, in response to a northward expansion of the summer warming. Subsequently, during deglaciation, intense warming initiating with the Bølling-Allerød, and interrupted during the Younger Dryas, led to an increase in the abundance of Globoconella inflata, suggesting year-round stratification. The Holocene was subdivided in three phases: an initial rapid warming (up to 10.4 ka cal BP), followed by the development of strong stratification during the second phase (10.4-5.3 ka cal BP), which includes the time interval of sapropel S1 in the Eastern Mediterranean. The second to third phase transition is marked by the appearance of Globorotalia truncatulinoides, signalling a strong seasonal contrast, characterised by strong winter mixing and summer stratification as evidenced also by the presence of N. incompta.

Keywords: Planktonic foraminifera, Neogloboquadrina incompta, reworked coccolith, Ligurian Sea, Last Glacial Period/Holocene, Mediterranean circulation