A proposed global boundary stratotype for the base of the Upper Series of the Ordovician System: The Fagelsang section, Scania, southern Sweden

A world-wide search for stratigraphic sections exposing the base of the Nem agraptus gracilis Biozone, the level selected to define the base of the glo bal Upper Ordovician Series, resulted in the recognition of three potential boundary stratotypes, namely the Fagelsang, Calera, find Dawangou sections , all of which hale been restudied during the last four years. These sectio ns fulfill most of the requirements for a GSSP, and their biozone boundarie s can be correlated precisely with each other: Based on an assessment of al l information now available, it is concluded that the Fagelsang section is slightly superior to the others as a global boundary stratotype. It has exc ellent and well-known graptolite and conodont biostratigraphy in a stratigr aphically continuous succession of uniform lithology, is readily accessible , and the key interval is nor affected by faulting. The boundary interval i s exposed in two natural outcrops that have not changed substantially for m ore than a century and the same interval is also present in two drill-cores from the Fagelsang region. Although having some drawbacks, the Calera and Dawangou boundary sections are likewise excellent in most significant respe cts and they are proposed to be selected as auxiliary stratotypes.