Thirty mudstone samples from coastal exposures of the Northumberland Formation on Hornby Island, British Columbia, Canada, yielded diverse dinoflagellate cyst and terrestrial sporomorph assemblages. A late Campanian age for the formation has been well defined through magnetostratigraphy, macrofossil biostratigraphy, and geochemical studies of the Hornby Island section. Dinoflagellate cyst taxa corresponding to 61 genera are exceptionally well preserved and include specimens referable to at least 68 formally established species. The earliest occurrences of Canninginopsis maastrichtiensis, Druggidium cf. discretum, Phanerodinium belgicum, Renidinium cf. vitilaire, Senegalinium simplex, Spiniferella cornuta, and Xenicodinium delicatum sensu Slimani et al. are reported along with the most recent occurrence of Senoniasphaera protrusa, extending their stratigraphic ranges into the upper Campanian. The palynomorph assemblages support a late Campanian age. Two dinoflagellate cyst ecozones are recognized (ecozone 1 and ecozone 2). Assemblages suggest sediment deposition in an inner shelf environment with moderate to high nutrient input and primary productivity.
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The authors wish to extend their gratitude to Dr. Rob Fensome of the Geological Survey of Canada, Bedford Institute of Oceanography, Nova Scotia for sharing his insights with respect to peridinioid cyst taxonomy and Dr. Dennis Braman of the Royal Tyrell Museum, Drumheller, Alberta for discussions pertaining to sporomorph taxonomic identification. This manuscript also benefited from highly constructive feedback provided by Dr. Martin A. Pearce of Evolution Applied Limited, Buckinghamshire, United Kingdom, Dr. Paul Dodsworth of StrataSolve Limited, Cheshire, United Kingdom, and two anonymous reviewers. Partial funding for this research was provided by the Natural Science and Engineering Research Council (NSERC) V.P. (Discovery Grant).
The dinoflagellate cyst assemblages, given the prevalence and concentrations of areoligeracean and nearshore gonyaulacacean cyst taxa, suggest an inner shelf depositional environment conducive to moderate to high nutrient input and primary productivity. This interpretation is supported by terrestrial and marine palynomorph ratios, abundances, and dinoflagellate cyst autofluorescence. The dinoflagellate cyst assemblages also enable a paleolatitudinal projection of a mid-latitude setting for the Nanaimo Basin, transitional between boreal and subtropical marine realms proximal to the terrestrial Aquilapollenites phytogeoprovince.
© 2018 Elsevier B.V.
- Dinoflagellate cysts
- North Pacific
- Northumberland Formation
- Pollen and spores