Comparison of the Holocene and Eemian palaeoenvironments in the South Icelandic Basin: dinoflagellate cysts as proxies for the North Atlantic surface circulation

Abstract

A precise assessment of the hydrological changes in the northern Atlantic Ocean throughout the last climatic cycle stands as one of the key priorities for understanding the mechanisms of global climate change. A high resolution micropalaeontological study of a sediment core (MD95-2015) retrieved from the South Icelandic Basin, allows us to infer patterns of North Atlantic surface hydrological changes during the present (Holocene) and the ultimate (Marine Isotopic Stage 5) Interglacial periods. The downcore distribution of organic-walled dinoflagellate cysts (dinocysts) is used, in conjunction with additional proxies (sediment magnetic susceptibility, CaCO 3, stables isotopes and planktic foraminifer assemblages) to identify climatic instabilities of various amplitudes. These events are mostly characterised by prominent changes in relative abundance of the dinocysts Spiniferites mirabilis and Operculodinium centrocarpum, whose maximum values are thought to trace sea-surface temperature peaks at the core site. Two hypsithermal periods are identified on this basis, between 126 and 120 kyr BP and from 9.2 to 5.7 cal kyr BP (∼8–5 14C kyr BP), respectively. Some discrepancies between the micropalaeontological tracers used are discussed here in the light of their qualitative and quantitative (transfer functions) ecological interpretation.