Palynostratigraphy of the classic Portland and Purbeck sequences of Dorset, southern England, and the correlation of Jurassic-Cretaceous boundary beds in the Tethyan and Boreal realms

Abstract

Abstract Placement of the Jurassic-Cretaceous boundary and its correlation between the Tethyan and Boreal realms are still contentious. The distribution of stratigraphically significant dinoflagellate cysts in the Portland Stone and Purbeck formations of the Isle of Purbeck, Dorset, UK provides a basis for direct correlation between these sections and the type Berriasian in southeast France. The base of the Berriasian — and thus of the currently accepted Jurassic-Cretaceous boundary — most probably lies at the base of the Cypris Freestones in the Purbeck Formation. Miospore correlation between the Dorset sections and ammonite-bearing rocks in the Spilsby Province suggests that the base of the Cretaceous lies close to the base of the Subcraspidites preplicomphalus zone in the Boreal Realm.