Palaeoproductivity changes and upwelling variability in the Galicia Mud Patch during the last 5000 years: geochemical and microfloral evidence

TheHolocenepalaeoclimatichistoryoftheGaliciancontinentalshelfhasbeeninvestigatedthrough theanalysesofdiatomremains,othersiliceouscompounds,biogenicsilica(BSi)andmetalscontentinamul- tiproxyapproachtoagravitycorerecoveredfromtheGaliciaMudPatch,NWIberianPeninsula,coveringthe last 5000 years. Downcore changes in diatom assemblages composition and abundance reflect changes in diatomproductionrelatedtolong-/short-termvariationsinclimate,regionaloceanography,upwellingstrength and river influx off the coast of NW Spain and Portugal. Palaeoclimatic variability was related to the relative strengths and position of the Azores High and Iceland Low pressure cells. Metals and microflora fluctuations are interpreted as changes in the riverine influence and upwelling intensity paced by oceanographic, atmos- pheric and climatic changes. Lack of diatoms between 4700-3300 and 1800-1200 cal. yr BP could be linked to early diagenetic processes taking place in the sediment after burial. Biogenic barium (Baexcess), metals and diatomassemblages,showageneralincreaseofmarineproductivityforthelast1200cal.yrBP.Between800 and500cal.yrBPhighproductionofthemicrofloraistriggeredbyinfluxofriver-derivednutrientsundercon- ditionsofSWwindsandstormsresultingfromaNAOnegative-likephase.Thebiosiliceousandgeochemical signatures of sediments from the last 500 cal. yr BP indicate conditions of enhanced upwelling and increased