Siliceous microfossils and agglutinated foraminifera from the Upper Cretaceous Smoking Hills and Mason River formations in the Smoking Hills area, Northwest Territories

Abstract

Five microfossil groups are herein described from the Upper Cretaceous Smoking Hills and Mason River formations in the Horton River area (Northwest Territories). Microfossil assemblages from the Smoking Hills Formation are dominated by radiolarians and foraminifera whereas the Mason River Formation mainly contains diatoms, silicoflagellates, and sponge spicules. These microfossil groups have been reported before in these units and age-equivalent strata from the Canadian Arctic except for radiolarians. The radiolarian assemblage described in this study represents one of the most diverse and abundant assemblages reported in Campanian-Maastrichtian rocks in North America and can be used to reconstruct the climatic, paleoceanographic, and paleobiogeographic conditions that took place at the end of the Cretaceous Period. This Open File documents the stratigraphic occurrence of the microfossil types.

Progress in the taxonomy of Late Cretaceous high-latitude radiolarians: insights from the Horton River area, Northwest Territories, Canada

“…Although the Smoking Hills and Mason River formations exhibit similar lithology, their microfossil content is markedly different (Diaz et al, 2020). The Smoking Hills Formation is dominated by radiolarians with sporadic, agglutinated foraminifera, diatoms and silicoflagellates.…”

“…The Smoking Hills Formation is dominated by radiolarians with sporadic, agglutinated foraminifera, diatoms and silicoflagellates. In contrast, the Mason River Formation is dominated by diatoms and silicoflagellates, contains only a few radiolarian taxa and is barren of agglutinated foraminifera (Diaz et al, 2020). The Smoking Hills and Mason River formations were deposited in an outer shelf-to-slope environment of the epicontinental marine Anderson Basin (Yorath and Cook, 1981;Dixon, 1992), located at approximately 80°N in the convergence between the Western Interior and Sverdrup basins.…”

“…Lithostratigraphic sections of the Smoking Hills and Mason River formations were described, measured and sampled (Smith et al, 2018;Diaz et al, 2020). The samples for this study were taken from the type sections of the Smoking Hills and Mason River formations described by Yorath et al (1975) (Fig.…”

“…At each sample point, the surface material, largely unconsolidated mudstone, was removed, and unweathered material was sampled and placed in plastic bags and sealed. Thickness measurements and lithology are reported in Diaz et al (2020) and Grasby et al (2022).…”

“…2). Diaz et al (2020) provided a preliminary list of the radiolarian assemblage recovered from the Smoking Hills Formation. The full radiolarian assemblages from both units and their biostratigraphic significance will be discussed in a future contribution.…”