Using microplankton proxies to evaluate marine palaeonvironmental changes during late Maastrichtian: Evidence from the More Basin (Norwegian continental shelf)

This work presents high-resolution palynological and micropalaeontological analyses of a cored succession across the upper Maastrichtian from a well in the More Basin (Norwegian continental shelf). Diverse assemblages of dinoflagellate cysts and foraminifera provide insights into the palaeobiogeography and palaeoenvironmental conditions during the late Maastrichtian in this region. An outer neritic setting is interpreted based on the general high abundance of planktonic foraminifera. A subdivision of the biostratigraphic record into three Ecozones has allowed for a detailed documentation of the phytoplankton communities during the late Maastrichtian until the K-Pg boundary. Ecozone A is characterised by a predominance of peridinoid cysts which together with abrupt fluctuations in planktonic foraminifera suggests high nutrient availability and, possibly, high terrestrial input potentially associated with regional turbiditic currents. Also, the occurrence of taxa characteristic of boreal affinity suggests colder waters for this Ecozone. Ecozone B is characterised by consecutive influxes of areoligeracean species such as Palynodinium grallator, Areoligera senonensis and Circulodinium distinctum in the dinoflagellate cyst assemblages. The increase abundances of planktonic foraminifera across this interval suggests an increase in palaeowater depth into a more outer shelf to upper slope. Immediately before the K-Pg boundary (Ecozone C), an increase in abundance of low latitude dinoflagellate species and the planktonic foraminifera Pseudotextularia elegans may represent the local signal of the global latest Maastrichtian Warming Event. Two new dinoflagellate cyst species restricted to the late Maastrichtian, Glaphyrocysta turgida sp. nov. and Heterosphaeridium silybum sp. nov. are also formally described. (c) 2021 Elsevier Ltd. All rights reserved.