The Jurassic-Cretaceous transition of Southern Sweden - palynological and sedimentological interpretation

Palynological studies on the Vitaback Clay help resolve the position of the Jurassic-Cretaceous boundary in southern Sweden. Well-preserved assemblages of terrestrial pollen and spores, together with abundant algae (Botrycoccus), and for the first time, dinoflagellates have been identified in the Vitaback Clay. A Berriasian age is corroborated for the Vitaback Clay based on the palynological data; the Jurassic-Cretaceous boundary being placed around the contact of this unit with the underlying "Nytorp Sand". The terrestrial vegetation was dominated by coniferous forest with an understorey of ferns in a warm, temperate climate. The palynoflora shows compositional similarities to the Northern Chinese Floral Province and especially the Jehol Group. The majority of the Vitaback Clay represents a moderate-to low-energy paralic succession. However, the basal part of the unit incorporates anomalously coarse material of mixed terrestrial and marine origin. This sedimentary package is herein interpreted to represent tsunami deposits and is similar to coeval tsunami-related deposits in France