Palynology of the Cenomanian to lowermost Campanian (Upper Cretaceous) Chalk of the Trunch Borehole (Norfolk, UK) and a new dinoflagellate cyst bioevent stratigraphy for NW Europe

Abstract

A high-resolution palynological analysis of the Cenomanian to Lower Campanian in the Trunch borehole, Norfolk (southern North Sea basin) is documented. This constitutes the most detailed continuous record of organic-walled dinoflagellate cysts (dinocysts) from a single Upper Cretaceous section to date. A revised stratigraphic framework for the Trunch succession is presented, integrating regional marker bed lithostratigraphy, macrofossil biostratigraphy and carbon-isotope chemostratigraphy. Palynological events at Trunch are compared to published records with an emphasis on NW Europe, and a new stratigraphy comprising 65 dinocyst events is proposed. A geochronological age model based on radioisotopic and astrochronological ages of macrofossil biostratigraphic datum levels and global carbon-isotope events (CIEs) is used to revise the age calibration of the Upper Cretaceous δ13Ccarb carbonate reference curve for the English Chalk, and to calculate absolute ages for the palynological events with an accuracy judged to be ±500 kyr. The palaeogeographic distribution of key taxa is presented based on records obtained from the PALYNODATA database and additional records, summarised to 212 sites world-wide. Endemic NW Europe, Northern Hemisphere-wide and global species distributions are demonstrated. A taxonomic and detailed stratigraphic discussion is provided to determine the likelihood that the events may be considered as global first or last appearance datum levels, or are local to regional lowest and highest occurrences. Four global, 21 Northern Hemisphere and 40 NW Europe events are tabulated, including 29 inceptions or extinctions of marker species; an additional 36 events may be of regional significance.