Holocene palaeoclimatic evolution in the North Ionian Basin of the Mediterranean Sea: A multiproxy approach

Abstract

We analyse the ND14Mbis gravity core obtained from the North Ionian Basin using a multi-proxy approach (calcareous nannofossils, planktonic foraminifera, geochemistry, X-ray fluorescence), to improve knowledge of Holocene palaeoclimatic and palaeoceanographic evolution. Wavelet analysis of the cold water coccolith species group (Emiliania huxleyi > 4 μm and Gephyrocapsa muellerae) reveals a 1.6 ky periodicity, which closely matches the 1.5 ky North Atlantic Bond cycles. On shorter timescales, our high-resolution analysis allows the identification of major climatic events, including the latter part of the African Humid Period (10–5.4 ky BP) and the deposition of the Sapropel 1 interval (S1, 10–6.6 ky BP), as well as the Pre-Roman (4.1–2 ky BP), Roman (2–1.5 ky BP) and Post-Roman (1.5–0 ky BP) periods. During the African Humid Period, the S1 interval is clearly marked by the distribution of Florisphaera profunda, Syracosphaera pulchra, Braarudosphaera bigelowii and warm water taxa (Calciosolenia sp., Discosphaera tubifera, Oolithotus fragilis, Rhabdosphaera clavigera, Umbilicosphaera sp. and Umbellosphaera tenuis), reworked coccoliths and XRF signals. Our findings show that S1 anoxic bottom-water conditions were interrupted during two short spells of climate cooling that coincide with the 8.2 and 7.4 ky BP climate events. Drier conditions developed at the end of the African Humid Period, with intermittent humid intervals. These episodes were likely governed by the negative shifts of the North Atlantic Oscillation system, whose influence progressively intensified after 4.2 ky BP, as reflected by the oscillations in holococcolith abundance and K/Al curves.