PALYNOLOGICAL INSIGHTS INTO COASTAL VEGETATION OF THE WEST COAST OF NORTH AMERICA ACROSS THE END-CRETACEOUS EXTINCTION EVENT

Land plants experienced a major turnover globally in the Cretaceous-Paleogene (K-Pg) mass extinction. Latest Maastrichtian–early Danian land plant diversity of the east coast of Vancouver Island, British Columbia, Canada, was analyzed based on pollen grains and spores from outcrops of the informally named and predominantly marine Oyster Bay Formation (OBF). The sampled ~80 m-thick outcrop is comprised of mudstone interbedded with sandstone and fine sand unconformably overlying the Upper Cretaceous Nanaimo Group. A well preserved palynoflora of ~101 taxa was recovered and changes in abundances before and after the K-Pg boundary interval are described. The classic ‘fern-spike’, characterised by spore taxa such as Cyathidites spp. and Laevigatosporites spp., was not observed. The palynoflora contains recognizable elements from the ‘Continental Margin’ floristic province characterized by Tschudypollis pollen that occurs throughout, although not abundantly, rare occurrences of Aquilapollenites pollen, and an absence of Normapolles pollen. Maastrichtian OBF palynofloras are dominated by spores with lesser counts of gymnosperms and angiosperms such as Tschudypollis spp., Arecipites spp. and other angiosperms that survive into the Danian, including Cupanieidites spp., other tricolpate and tricolporate pollen (with affinities to Betulaceae and Juglandaceae), and members of Sparganiaceae. Spores from lycopods (incl. Retitriletes spp. and Camarozonosporites spp.), ferns (incl. Cibotiumspora sp., Cyathidites spp., and members of the Gleicheniaceae, Osmundaceae, Polypodiales and Schizeaceae s.l.), cycads (Cycadopites spp.), and conifers (bisaccates and Cupressaceae) also occur. The near coastal/marine depositional environment also features Nyssa spp., and the mangrove palm Nypa (as Spinizonocolpites)—a taxon also known from sites at the southern end of the Western Interior Seaway and near the Chicxulub impact crater. Although at probable mid-latitude, this site must have experienced a megathermal climate that supported abundant warm-adapted plants such as palms and mangroves. This study will also undertake geochemical determination of the K-Pg boundary through analysis of iridium indicative of the extra-terrestrial bolide impact.