Variations in ratios of chorate (C) dinoflagellate cysts to proximo-chorate (P), proximate (P) and cavate (C) forms recovered from the Rhodano-Swabian sedimentary basin in northern Switzerland have been correlated with sequence boundaries and sedimentary cycles established for this basin. The variations in these ratios and abrupt increases and decreases in the number of recorded species from the same strata corroborate closely the sequence boundaries established by Gygi et al., (1998) using other parameters such as lithology and macrofossil content of the sediments. Highstands of sea level are marked by an abrupt increase in species diversity and in C: PPC ratio. In contrast, lowstands are indicated by rapid decline in the abundance of species and a decrease in C: PPC ratios.
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