10,000Â years of vegetation history of the Aa palaeoestuary, St-Omer Basin, northern France

The analysis of sediments and pollen from three sedimentary profiles in the St-Omer basin (Pas-de-Calais, France) has allowed the reconstruction of local and regional vegetation history from the late Preboreal to the Subatlantic. Hydrological changes induced vegetation changes, with freshwater marshy vegetation dominating during fluvial episodes, and halophilous grasslands, typical of shore areas, dominating during episodes of salt water input (five marine episodes, so-called St-Omer I to St-Omer V). Pollen markers indicative of human presence and agricultural activities, along with contemporaneous signals of forest disturbance, are recorded from ca 4000 cal BP onwards.