Martins, V., Sequeira, C., Jouanneau, J., Weber, O. and Rocha, F. 2007. Multiproxy study of Ria de Vigo sedimentation during the late Holocene (last 2600 years). Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 258 – 262. Gold Coast, Australia, ISSN 0749.0208

The main aim of this work is to identify changing and characterise the hydrographical regime in the outer sector of the Ria de Vigo during the late Holocene. Sediment samples were collected every centimetre along the core KSGX 24 and used for textural, mineralogical and microfaunal studies (benthic foraminifera). The age model was based on four AMS radiocarbon dating. This sedimentary sequence recording the last ∼3 ka cal BP has a mean grain size varying between 13-26 µm. Fine fractions represent 76-92 % of the bulk sediment. Detrital minerals are the main constituents of the sediments (55-85 %). A total of 202 benthic foraminiferal taxa were identified. A significant amount of tests belongs to exotic species. Two finer sections were identified between 175-75 cm and 35-0 cm. These sections are characterised by the slight increase of detrital minerals and by the decline of carbonated minerals. In the first section the percentage of benthic foraminifera tests supplied from deeper waters and the percentage of the species related with high flux of organic matter, increased. These results suggest the occurrence of a higher oceanic influence in the Ria de Vigo, between ∼2.2-1.2 ka cal BP, probably induced by stronger up-welling events followed by periods of relaxation which were followed by weaker events of downwelling. During the later period between ∼0.5-0 ka cal BP it is possible that stronger up-welling events may have occurred, followed by stronger down-welling events which have probably enhanced the vertical water mixing and caused lower retention of sediments inside the outer sector of the Ria.