The Llandovery-Wenlock Boundary in the Northern Part of the Baltica Paleocontinent

摘要

The Llandovery-Wenlock boundary was defined in its type section at Hughly Brook, Welsh Borderland as a level coinciding with the contact between the Purple Shale and Buildwas formations. Although no grapto-lites were recorded from the type section, it has been assumed that the base of the Cyrtograptus centrifugus graptolite biozone correlates with the base of the Wen-lock Series.