Coastal salt-marshes as geological archives of recent sea-level changes

In order to evaluate the accuracy and regional significance of salt-marsh reconstructions of former sea level based on foraminiferal transfer functions, we have calibrated the foraminiferal assemblages of a saltmarsh core from the Urdaibai estuary using the regional transfer function constructed previously for the southern Bay of Biscay. The foraminifera-based reconstructions were placed into a temporal framework using Pb-210, heavy metal concentrations, and Cs-137-derived sediment accumulation rates. The resulting relative sea-level curve has been compared with the nearest tide-gauge data (Santander) and with other geological records from regional salt-marshes. Relative sea-level trends from core sediments support in all cases the idea of accelerating sea levels over the last century when compared to previous centuries, providing a regional relative sea-level rise of 2.0 mm yr-1 for the 20th centur