Geochemical Fingerprints of Climatic Oscillations during the Late

This work studies mineralogical data from X-Ray Diffraction Techniques (XRD) and geochemical data analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) of fine fraction from samples collected along the Ocean Margin Exchange Project (OMEX) core KSGX 24. This core was recovered in the external sector of Ria de Vigo, N Spain. Radiocarbon ages allowed the estimation of an age about 3 ka cal BP for the core base. Core KSGX 24 is a muddy sedimentary sequence with two main sections where the sediments are finer: ≈134-90 cm and ≈26-0 cm. These finer sections are characterized by a relatively low sedimentation rate, and by changes in the geochemical and mineralogical composition of the sediments and their magnetic susceptibility. Basically, they are relatively depleted in carbonates and Ca content, and relatively enriched in detrital minerals, namely phyllosilicates, and in Al, Co and Sc. The slightly coarser grained intercalated sections are marked by the increase of Ce, La and Th content. These results suggests that, despite the prevalence of a weak hydrodynamic regime in the study area during the last 3 ka, it has undergone some changes. The mineralogical and geochemical deviations may have been conditioned by several factors, such as: authigenetic and diagenetic reactions; anthropogenic activities in the nearby continental region; the natural tendency for sea level rise; changes in hydrodynamic conditions regulated by modifications in the pattern of prevailing winds; and alterations in the rainfall regime. The two last factors are related to climate oscillations and probably with the tendency of the North Atlantic Oscillation (NAO) to remain more positive or negative during longer periods in the past than at present.