Upper Cretaceous diatom biostratigraphy of the Arctic archipelago and northern continental margin, Canada

Abstract

Strata in the Canadian Arctic contain diverse and moderately well-preserved Late Cretaceous siliceous microfossil as- semblages. One-hundred-twelve samples were analyzed from a composite stratigraphic section (1094m-thick) of the Smoking Hills, Mason River and Kanguk formations. Four sections were examined: (1) Slidre Fjord on Ellesmere Island; (2) Hoodoo Dome on Ellef Ringnes Island; (3) Cape Nares on Eglinton Island; and (4) Horton River on the Anderson Plains, Northwest Territories. Two hun- dred-three diatom taxa were identified in forty-nine productive samples. Four Upper Cretaceous diatom zones are proposed for the Ca- nadian Arctic based on the biostratigraphic distribution of diatoms: (i) the Upper Cenomanian to Upper Santonian(?) Gladius antiquus Concurrent Range Zone, (ii) the Lower Campanian Costopyxis antiqua Partial Range Zone, (iii) the lower Upper Campanian Trinacria indefinita Interval Zone, and (iv) the upper Upper Campanian Stephanopyxis simonseni Partial Range Zone. The diatom assemblages are similar to those of Alpha Ridge (Arctic Ocean), Ural Mountains (Russia), and Campbell Plateau (SW Pacific Ocean), enabling diatom-based biostratigraphical correlations within the northern high-latitudes and to the southern high-latitudes. A fifth biostratigraphic zone, Azpeitiopsis morenoensis Concurrent Range Zone, is also proposed, based on common and widespread distribution of the nominative taxon in lower to upper Maastrichtian sediments. Sufficient data is now available to establish the construction of a diatom-based standard zonal framework for the Upper Cretaceous. Two new combinations, Trochosira denticulatum (Strelnikova) Tapia and Trochosiropsis polychaeta (Strelnikova) Tapia are here proposed.