Evolución paleoecológica de la Ría de Vigo (NO de España) durante el Holoceno

Abstract

Three vibro-cores from the central axis of the Ria de Vigo (Rias Baixas, Galicia, NW Spain) have been analysed in order to interpret the paleoecological conditions in the Ria during the Holocene. Different sedimentological parameters, mainly benthic foraminifera assemblages have been used to reconstruct the paleoenvironment. The cores VIR-37 and VIR-18 are similar lithologically, they are mainly composed of dark green mud. The core VIR-14 (shallower than the former two) records in the base a weathered granite overlain by a sedimentary succession of siliciclastic gravel, green mud, and bioclastic gravel composed of fragments of the red algae Lithothamnium sp. J

Two different periods can be identified. From 2.9 ky to 500 yB.P. the Ria de Vigo was a relatively confined environment with a fluvial influence stronger than that of today which caused rapid and frequent salinity variations. The abundant organic matter preserved in the sediments was mainly of a continental provenance. Since 700 y B.P. the exchange of waters between the Atlantic Ocean and the ria has increased. The present environmental conditions were attained by 500 y B.P. During this second period the dynamics were governed by the influence of oceanic water and seasonal upwellings. The waters were colder, more oxygenated, and the combined effect of high biological production and a high sedimentation rate enhanced the preservation of the organic matter