Dinoflagellate cysts have been used extensively for reconstructing paleoenvironments in the Paleogene (see overview in Sluijs et al., 2005), as they are particularly sensitive to changes in salinity, temperature, and nutrient levels (Powell et al., 1992; Pross and Brinkhuis 2005; Sluijs et al., 2005). We calculate “%low salinity dinoflagellate cysts” (Figs. 7–9) by grouping cysts of similar inferred ecologic preferences (see Fig. 7, and discussion in the Supplementary Material) to provide an indication of environmental change, and by excluding species of uncertain affinity such as Apectodinium. Samples with fewer than 20 specimens were also excluded. Despite the limitations of this method, the large variation in the %low salinity dinoflagellate cysts (ranging from 0% to 80%) clearly indicates that significant environmental changes in surface water conditions occurred during the CIE onset in the central North Sea, and is supported by coeval changes in the sedimentary carbon/nitrogen (C/N) ratio (Fig. 10) which reflects changes in the proportion of terrestrial/marine organic material deposited in the North Sea Basin due to terrestrial runoff and productivity (see Section 4.4).
specimens
20
Samples
%low salinity dinoflagellate cysts
0% to 80%
%