MARINE RADIOCARBON RESERVOIR EFFECT IN SOUTHERN ATLANTIC IBERIAN COAST

Research concerning the variability of the marine radiocarbon reservoir effect (Delta R) in the southern Iberian Atlantic coast confirms the existence of different. R values for regions that correspond to different oceanographic conditions. Due to these oceanographic conditions, the southern Iberian Atlantic coast can be divided into 3 zones: the Barlavento (windward), where the coastal waters are influenced by an intense upwelling of the northeastern Atlantic circulation (positive Delta R values); the Sotavento (leeward), where an upwelling area of minor intensity occurs; and the Andalusian coast, where because of its configuration does not present any wind-driven coastal upwelling (negative Delta R values). For the first time,. R values were determined for the Sotavento coastal region and, at the same time, new Delta R values were calculated for the Barlavento and the Andalusian coast for the last 3000 yr taking into account the data already obtained but now using a new methodology for calculation. In this way, Delta R weighted mean values were determined for the 3 regions of the southern Iberian Atlantic coast: Delta R = +69 +/- 17 C-14 yr (Barlavento), Delta R = -26 +/- 14 C-14 yr (Sotavento), and Delta R = -108 +/- 31 C-14 yr (Andalusian coast). These values are in accordance with the different oceanographic conditions prevailing in these coastal regions. The data also allow identification of a Bond event at 0.8 ka cal BP and a drastic change in the oceanographic conditions in the Barlavento and Andalusian coastal areas during the 5th millennium cal BP.