Late Holocene climatic oscillations traced by clay mineral assemblages and other palaeoceanographic proxies in Ria de Vigo (NW Spain)

Authors : Virgínia MARTINS, Fernando ROCHA, Cristina SEQUEIRA, Paula MARTINS, José SANTOS

Pages : 398-413

Doi:10.3906/sag-1211-39

View : 16 | Download : 6

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies insert ignore into journalissuearticles values(granulometric, geochemical, geochronological and microfaunal);, in the core KSGX 24. A Benthic Foraminifera High Productivity insert ignore into journalissuearticles values(BFHP); proxy was used to determine changes in the flux of organic matter insert ignore into journalissuearticles values(OM); at the bottom of the study area. Total organic carbon insert ignore into journalissuearticles values(TOC); content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes. The sedimentation was finest in 3 sections: ~ 230-214 cm, ~ 185-73 cm and ~ 20-0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content. The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to well-known periods, such as the first cold period of the Upper Holocene insert ignore into journalissuearticles values(~ 2.9 ka cal BP);, the Dark Ages insert ignore into journalissuearticles values(between ~ 2.2 - 1.2 ka cal BP); and the Little Ice Age insert ignore into journalissuearticles values(~ 0.6 ka cal BP);.
Keywords : Paleoclimatology, historical climatic oscillations, benthic foraminifera, multiproxy approach, upwelling