Sediment accumulation rates in the southern Barcelona continental margin (NW Mediterranean Sea) derived from 210Pb and 137Cs chronology

20 pages, 8 figures, 1 tableSediment cores were collected from the southern Barcelona continental margin, including the Foix canyon, in order to study sediment accumulation in this area. For this purpose, 210Pb, 137Cs and, to a lesser extent, 239,240Pu and heavy metals, were determined in sediment sections using state-of-the-art techniques. 210Pb concentration profiles and 137Cs, 239,240Pu and heavy metals profile features were used to establish the sediment chronologies. Further information was also obtained from granulometric analyses. The magnitudes studied and correlated in this work included surface activities, mixing rates, accumulation rates and inventories. Sediments on the continental shelf showed a varied degree of mixing (except possibly CN-23), sedimentation rates were relatively small and the sedimentary material probably had a common origin. Cores from the slope showed less mixing and, in cores CN-36 and EB-2, located in the Foix canyon axis, the 137Cs signal vs. depth was clear and well preserved. Accumulation rates and total 210Pb inventories were maximum in core CN-36 at mid-slope of the canyon, which was considered to be an active depocenter. Core CN-38, collected on the open slope, showed a much smaller accumulation rate. Therefore, it was concluded that shelf material is being transported alongshore by the prevailing currents and becomes focused in the canyon, which is acting as a natural trap. Within the canyon this material is preferentially deposited at a mid-slope depocenter. Little extra material reaches the lower canyon area. In this area, core EB-2 appeared to show signs of the presence of resuspended material, possibly derived from the canyon walls. Finally, observed changes in sedimentation rates during the 1930s could not be explained on the basis of current knowledge and this is suggested to be an important subject for further researchThe authors wish to acknowledge financial support received from the European Union (Euromarge-NB, MAST contract MAS2-CT930053), and the Spanish government (CICYT, Project Concentra, AMB92-0251-C01) to carry out this researc