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CR 48:247-259 (2011)  -  DOI:

Palaeoclimatic changes in the NW Iberian ­Peninsula during the last
3000 years inferred from ­diagenetic ­proxies in the Ría de Muros
sedimentary record

A. Andrade, B. Rubio*, D. Rey, P. Álvarez-Iglesias, A. M. Bernabeu, F. Vilas

GEOMA, Marine and Environmental Geology Group, Department of Marine Geosciences, University of Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain

ABSTRACT: The Ría de Muros is the northernmost of the 4 Rías Baixas and, like the others, is subject to seasonal upwelling. The high organic carbon content of its sediments (average 2.4%) is due to the consequent high primary production together with significant continental input from river discharge and runoff. This high organic carbon content not only favours early diagenesis, but does so to an extent that depends on the relative proportions of labile marine organic carbon and refractory terrestrial organic carbon. Thus, changes in early diagenesis reflected in the mineralogy and/or composition of the Ría’s sediments can throw light on the degree of oceanic influence in the Ría, and hence on changes in the circulation and ventilation of its water masses and/or the climate on shore. In this study of sediment cores taken in the outer Ría de Muros, the combined use of textural analysis, magnetic properties (magnetic susceptibility [κ], ratio of anhysteretic to isothermal remanent magnetisation [ARM:IRM], and median destructive field [MDF]) and geochemical parameters (total concentrations of diagenetically stable and mobile elements in sediment and pore water) allowed the identification of a current redox front and 2 palaeosedimentary redox fronts in the sediment record. These fronts originated during periods of high marine/terrestrial organic matter ratio (as inferred from the ratio of total organic carbon to total nitrogen [TOC:TN] and δ13C). Sedimentation rates calculated from 14C dating results identify these periods as known periods of increased upwelling and reduced continental input due to colder, drier climate in the NW Iberian Peninsula, namely the Little Ice Age, the Dark Ages, and first cold period of the Upper Holocene.

KEY WORDS: Upwelling · Ría de Muros sediments · Organic matter origin · Diagenesis · Upper Holocene palaeoclimate

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Cite this article as: Andrade A, Rubio B, Rey D, Álvarez-Iglesias P, Bernabeu AM, Vilas F (2011) Palaeoclimatic changes in the NW Iberian ­Peninsula during the last
3000 years inferred from ­diagenetic ­proxies in the Ría de Muros
sedimentary record. Clim Res 48:247-259.

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