Variations in terrigenous dilution in western Mediterranean Sea pelagic sediments in response to climate change during the last glacial cycle

Hemipelagic intervals in four giant Calypso piston cores from the Balearic Abyssal Plain (western Mediterranean Sea) were studied in order to determine fluctuations in the supply of terrigenous sediments to the basin during the last 130,000 years and possible climatic modulation of terrigenous sediment and particle flux. Carbonate records from hemipelagic intervals in these cores display distinct 'Atlantic' type cycles, where glacial periods show, on average, 20% lower calcium carbonate contents than interglacial period equivalents. The decrease in calcium carbonate seen during glacials may be the result of increased dilution by terrigenous (aeolian and fluvial) particles derived from aeolian and/or fluvial sources. Higher glacial aeolian particle fluxes to the western Mediterranean Sea may have been caused by changes in the prevailing atmospheric conditions, resulting in drier and colder climatic conditions in the source areas and more frequent and intense outbreaks of dust transport. The colder and drier climatic conditions in combination with a lowered sea level would allow rivers to dump their sediment load closer to the shelf edge, promoting enhanced fluvial input into the basin. Besides significant calcium carbonate variations that correlate with glacial/interglacial cycles, several short-term abrupt changes in the calcium carbonate content are recorded, which appear coincident with enhanced magnetic susceptibility values, especially the events within Marine Isotope Stage (MIS) 3. The timing of these short-term events may be linked with cooling events in the North Atlantic, particularly Heinrich Events and cold events within MIS 5. These short-term trends may possibly be explained by increased terrigenous particle transport, due to drier and colder climate in the Mediterranean borderlands. Our results further show that about 90% of the sedimentary sequence of the Balearic Abyssal Plain consists of turbidites. Generally, these appear not to have caused significant erosion, and an almost complete continuous time stratigraphy is present in the intercalated hemipelagic intervals. (C) 2004 Elsevier B.V. All rights reserved.