Distribution of foraminifera in salt marshes along the Atlantic coast of SW Europe: Tools to reconstruct past sea-level variations

Surface sediments were sampled from the salt marshes of the Morbihan Gulf (Brittany, France), the Barbadun, Plentzia and Urdaibai estuaries (Basque Country, northern Spain), the Minho and Lima estuaries (northern Portugal) and the Sado estuary (southern Portugal), to study the vertical distribution of foraminifera and their potential use for sea-level studies along the Atlantic coasts of SW Europe. The most abundant species found in the marshes are Jadammina macrescens and Trochammina inflata, with Miliammina fusca and Arenoparrella mexicana as secondary species, but there are some important regional differences in the composition of the foraminiferal assemblages. In the Basque marshes, Haynesina germanica and Ammonia tepida are dominant species, whereas in northern Portugal the most abundant species are M. fusca, Haplophragmoides spp. and T. inflata together with J. macrescens. Local transfer functions for sea-level reconstruction were constructed from fossil foraminiferal assemblages using Partial-Least-Squares (PLS) regression for data sets with a linear distribution (Morbihan and Sado) and Weighted-Averaging-Partial-Least-Squares (WA-PLS) regression for data sets with unimodal foraminiferal distributions (Basque and Minho-Lima). The most accurate models were obtained from high marsh assemblages. The transfer function models provided errors of ca. ±0.10 m, indicating that precise reconstructions of former sea levels are possible in this area.