A review of the Andrarum Limestone and the upper alum shale (Middle Cambrian) of Bornholm, Denmark

Abstract

The lithology and fossil content of the Middle Cambrian Andrarum Limestone on Bornholm is briefly re­viewed. Trilobites, brachiopods and hyolithids are common, acid residues contain a rich fauna of pelagiel­laceans, rostroconchs and echinoderm fragments. Most of these are phosphatized with well preserved mi- cro- and ultrastructures. A revised list of trilobites is presented. New finds of trilobites in the lowermost upper alum shale show the lower part of the Lejopyge laevigata Zone to be no more than 10 cm thick. The occurrence of the Upper Cambrian conodont Westergaardodina tricuspidata permits a more exact place­ment of the Middle-Upper Cambrian boundary. The Middle Cambrian deposits are shown to be 3 m ± 10 cm in total thickness in the two localities known on Bornholm.