SEM-observation of calcareous micro- and nannofossils incertae sedis from the Silurian of Gotland, Sweden: Preliminary results

SEM observations of polished, sligthly etched rock samples from limestone-m arl alternations of the Silurian of Gotland allowed the discovery of numero us excellently preserved calcareous micro- and nannofossils, most of which remained unknown to date. Only few morphotypes can be assigned with varying degrees of confidence to groups which are already described in literature. The assemblages include possible ancestors of the foraminifera (Parathuram mina, Caligella, etc.), numerous algal remains (Girvanella, Halysis, etc.), very abundant small spherical calcitic microfossils ("nannospheres" or "ca lcispheres") as well as several enigmatic groups of microorganisms ranging in size between 5 and 100 mu m.