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.

Abstract Worldwide distribution of dinoflagellate cysts from the Aptian and Late Albian periods has been reported on palaeogeographical maps. A total of 32 and 38 species, derived from 36 and 70 studies located in the Northern Hemisphere and 14 and 17 studies in the Southern Hemisphere respectively, have been encountered in the literature. Based on their geographical range, we have defined Aptian cosmopolitan, restricted cosmopolitan, Boreal, Austral, Tethyan and restricted to the Northern Hemisphere taxa, with Late Albian Tethyan, Boreal and Austral taxa. The assemblage distribution has enabled the definition of sea-surface temperature (SST) gradients from 70°N to 70°S and latitudinal climatic belts and the establishment of preliminary biomes. Warmer conditions were found in southern latitudes compared to northern latitudes, as indicated by the worldwide distribution of Tethyan subtropical species. The asymmetric configuration of SST gradients is the same for both the Aptian and Late Albian periods. An estimation of the temperature requirements of extinct planktonic dinoflagellates is obtained by combining estimated temperatures from δ 18 O from fish teeth, belemnites, oysters and TEX 86 ratios related to latitude with the latitudinal distribution of their cysts. Aptian and Albian Tethyan currents with tropical-like temperatures close to 22 °C and 24 °C, respectively, reached 60–70°S.