Reconstruction of sedimentary environments in Holocene coastal deposits of the southwest Netherlands; the Poortvliet boring,a case study of palaeoenvironmental diatom research

Diatoms are valuable indicators of palaeosedimentary environments in coastal wetlands. In this paper, the utilization of diatoms in coastal reconstructions will be demonstrated in a case study, the Poortvliet boring (southwest Netherlands). Diatoms supply valuable information about palaeosalinity gradients and palaeotide levels in addition to the existing geological data set, obtained from sediment cores.The ecological data of taxa are usually gathered from diatom studies in recent coastal environments. The study of the Poortvliet boring shows that information can also be obtained from the past (the past as key to the past) by comparing the trends of the relative abundances of species of which the ecology is well-known to those of which the ecology is unknown. It is argued both on recent and fossil data that Cymatosira belgica and Rhaphoneis minutissima have a tychoplanktonic life form.