Chitinozoan biostratigraphy of the Middle Ordovician Dalby Limestone in the Fjäcka section, Siljan district, Sweden

The main section at Fjälcka, Dalarna, is a classic Ordovician locality in Sweden. It is the type section of three North Atlantic conodont zones and subzones, three Baltoscandian chitinozoan zones, and several topoformations. Detailed analysis of chitinozoan distribution in the Middle Ordovician Upper Dalby Limestone showed varying thickness of chitinozoan biozones caused by block movements, as well as clear variations in the content of acritarchs and organic-walled fossils in different blocks. Nevertheless, the succession of the East Baltic Kukruse and Haljala stages was established in one part of the section, and a composite section was worked out in spite of some complications caused by tectonic dislocation of beds.