Taxonomic Composition, Paleoecology and Biostratigraphy of Late Cretaceous Diatoms from Devon Island, Nunavut, Canadian High Arctic

Diatoms are the most diverse group of algae, playing a major role in global carbon and silicon cycles (Kidder and Erwin, 2001; Armbrust, 2009) and inhabiting virtually any environment that provides moisture and sunlight (Mann, 1999). Thus, they offer important information to help reconstruct paleoen-vironments and clarify stratigraphic relationships. Their strati-graphic range extends down at least to the Lower Cretaceous (Harwood et al., 2007). Available records list over 20 important Late Cretaceous occurrences of fossil diatoms, including: These occurrences document a variety of habitats to which diatom taxa were adapted, with specific environmental preferences, morphological features and assemblage characters that can be used to infer variations in paleoenvironmental setting. The distribution of these assemblages indicates that dia-toms were already abundant, widespread and diverse by the end of the Cretaceous (Harwood et al., 2007). Calculations of various authors estimate the number of Cretaceous diatom genera to be around 80 From one siliciclastic rich, deltaic shelf sequence in the Antarctic Peninsula Harwood (1988) reported nearly 200 diatom taxa. Nevertheless, Cretaceous diatom fossils are generally sparse, and our limited knowledge is mainly due to the temporal instability of the opal-A (Littke et al., 1991) that forms diatom frustrules (Tapia and Harwood, 2002). Fortunately , numerous Cretaceous diatom-bearing deposits are known from polar regions, particularly the Arctic. The often excellent preservation of diatoms in these areas allows to establish a more complete understanding of diatom paleocom-munities and biostratigraphic sequences than sites located at lower latitudes, and offers an excellent resource for morphological and taxonomic studies. Abstract Upper Cretaceous sediments of the Kanguk Formation exposed in Eidsbotn and Viks Fiord grabens on Devon Island, Nunavut, Canadian High Arctic, yielded 91 fossil marine diatom species and varieties (including indeterminate taxa), representing 41 genera. Excellent preservation of the assemblages was aided by shallow burial, protection in down-faulted linear grabens, and the presence of abundant volcanic material. Planktonic species and resting spores comprise nearly 70% of the diatom assemblage, and provided abundant food resources for the Late Cretaceous Arctic ecosystem. Deposition of the approximately 225 m-thick stratigraphic sequence was predominantly in a shallow marine neritic setting, with an upward progression to interbedded terrestrial deposits of the Expedition Fiord Formation, reflecting a regression and eventual persistence of terrestrial facies into the Early Cenozoic. The Kanguk Formation is widespread across the Canadian Arctic, and diatom biostratigraphy indicates a Santonian–Campanian age for the sequences reported herein, based on the presence of …