Glacial-interglacial variability of particle accumulation in the Canary Basin: a time-slice approach

Particle supply and sediment accumulation in the Canary Basin are strongly modified by seasonal coastal upwelling and dust input from the Sahara. Along an E-W depth profile and fertility gradient north of the Canary Islands, we demonstrate an increase in total mass accumulation rates from a low of 1-2 g cm(-2) ka(-1) in the outer oceanic domain to 6-12 g cm(-2) ka(-1) closer to the Moroccan shelf in Holocene sediments. During the Last Glacial Maximum (LGM, oxygen isotopic event 2.2), a steeper gradient was found, with two to four times higher mass accumulation rates at the near-shore sites. Total mass accumulation rates during the Last Interglacial Climax (LIC, isotopic event 5.5) and end of the Penultimate Glaciation (ePG, isotopic event 6.2) resemble Holocene values, with lowered near-shore maxima of 3 and 4 g cm(-2) ka(-1), respectively. Analyses of separate sediment components show that total organic carbon, total carbonate, lithogenic and diatom accumulation rates were generally enhanced during glacial times, especially during the LGM. In contrast, glacial accumulation rates of biogenic carbonate particles (coccoliths and planktic foraminifera shells) remained constant or were lowered with respect to interglacial time periods at the site closest to the Moroccan shelf, despite a doubling of bulk carbonate accumulation. This could indicate lowered supply from the productive euphotic zone or a latitudinal, offshore shift of the main sedimentary depocentre. However, enhanced carbonate dissolution could by itself account for this decrease in biogenic carbonate accumulation. Increased glacial input of detrital carbonate, derived from the exposed Moroccan shelf, appears to be responsible for the overall enhanced carbonate accumulation at the same sites, east of Lanzarote. (C) 2002 Elsevier Science Ltd. All rights reserved.