Asociaciones de foraminíferos bentónicos en el Holoceno de la ría de Vigo: interpretación paleoecológica.

Abstract

The sedimentological and micropaleontological characteristics of three vibrocores from the ria de Vigo (Galicia, NW Spain) have been analysed in order to interpret the paleoecological evolution of this area during the last 2.900 cal yr. B.P. Benthic foraminifera assemblages show the relation with different environmental parameters that played an important role during this part of the Holocene. We distinguish two different periods; a) from 2.900 cal. Yr. B.P. to 1.000 cal. Yr. B.P. the assemblages were dominated by euryhaline species, as Ammonia beccarii, and by taxa adapted to organic matter-rich and/or poorly oxygenated environments, as Bulimina spp. These facts allow us to infer an attenuated interchange of waters between the ria and the open ocean. b) from 1.000 cal. Yr. B.P. to the present, in the deepest and more external area of the ria, the planktonic foraminifera percentage increases and the benthic foraminifera assemblages show a conspicuous change. At the first moment, the epifauna became more abundant and afterwards the opportunistic Eggerelloides scabrous is progressively more frequent. These changes coincide with the onset of a water dynamic like the present one, which is determined by the influence of oceanic waters and the seasonal. As consequence, the shallower sea floor from the northern margin was colonised by calcareous algae that support an abundant benthic epifauna.