Chitinozoan biostratigraphy and lithological characteristics of the Lower and Upper Visby boundary beds in the Ireviken 3 section, Northwest Gotland

The lithology of the middle part of the cliff section at Ireviken 3 is described and the succession of chitinozoans through the Lower and Upper Visby formations is documented. Ten chitinozoan event levels are identified, based upon appearances or disappearances of chitinozoan taxa. Of these, all but two are considered to reflect local, rather than basinwide, changes in assemblages. Correlation of two chitinozoan event levels with Estonian and Latvian sequences is possible: level 1 may correlate with the base of the Margachitina margaritana Biozone and level 8 approximately with the base of Interzone IV.