Climatic and oceanographic changes for the last 25 cal ky bp in the Alboran seaA diatom inference.

Abstract

2043 (36°09'N/2°37.269 'W). In order to establish a stratigraphic time framework the age model is based on seventeen uC-dates, AMS radiocarbon ages measured on monospecific foraminiferal samples (C. bulloides). uC-dates were calibrated to calendar years in order to correct natural variations of UC. The CAUB 4.1 program was used for the calibration of uC-dates time record considered in this study that spans the last 26.5 cal ky BP. Average sedimentation rate for the time interval studied is 35.85 cm/ky. Based on the diatom record, paleoceanographic conditions favoured an increase in paleoproductivity during the Last Glacial Maximum (LGM) with a maxima occurred at ca. of Termination la (Tía), and during the Younger Dryas event (YD). During this period, meteorological conditions, with increased westerlies, would induce an intensified eastward flow which would displace the Western Anticyclonic Cyre (WAC) to the East A possible displacement of the North Alboran upwelling system has also be considered. The major component of the diatom assemblage during the YD are the resting spores (RS) of l.eptocylindrus danicus. The development of this species was probably favoured by the presence of the cooler and less saline Atlantic Surface Water (ASW) triggered by the diversions of meltwaters from the ice sheets surrounding the Atlantic. The abundance of fresh-water diatoms was used as an aridity indicator, while opal phytollths were linked to relatively wet conditions on land. During marine isotopic stage 2 (MIS2) until 1 4 cal ky BP the region supported a gradual climatic deterioration with a belt-grass loosing. Wind intensification was also deduced. During the B0lling-Aller0d (B-A) climatic conditions would be warmer and moister. This conditions prevails until ca. 8 cal ky BP. When the re-establishment of vegetation belts and replenish of lakes were deduced. Nevertheless, during the YD climatic conditions could be dryer and windy