HISTORY OF THE LAST DEGLACIATION IN THE ALBORAN SEA (WESTERN MEDITERRANEAN) AND ADJACENT NORTH-ATLANTIC AS REVEALED BY COCCOLITH FLORAS

A series of cores recovered from the Alboran Sea (western Mediterranean) and the adjacent part of the North Atlantic has revealed very high rates of accumulation which have enabled us to identify the stages of the last deglaciation in great detail. Isotopic analyses of the cores show the two steps of the deglaciation (terminations 1A and 1B) separated by the Bolling/Allerod warm phase. 14C dating of the cores has allowed the dating of the climatic succession. We have identified each event of the deglaciation on the basis of changes in the coccolith flora, especially in species of the genus Gephyrocapsa. Such changes reflect surface water changes since coccoliths live only in the photic zone. The abundance of G. muellerae in the cold intervals prior to each termination is greater than that in the Bolling/Allerod and Holocene warm intevals which follow the terminations. Conversely G. oceanica is virtually absent during cold intervals but becomes more common during the warmer periods. During the first deglacial warming there is a large influx of fine grained detrital material, presumably derived from increased run-off from the nearby mountains of southern Spain and north-west Africa. In the Alboran Sea cores with the most expanded sections, there is a marked increase in the percentage of Syracosphaera histrica at the beginning of this increase of detritus. No increase was found in the Atlantic core at this time.