Benthic foraminiferal biostratigraphy and morphogroup response to spatial and temporal variation in paleo-redox conditions of the Upper Cretaceous Kanguk Formation, Canadian Arctic Archipelago

The Kanguk Formation, a unit of dominantly organic-rich shale to siltstone deposited in the Sverdrup Basin, represents a significant portion of the Late Cretaceous record in the Canadian Arctic and has been regarded as a potential hydrocarbon source. Recent studies have identified OAE 2, a global oceanic anoxic event associated with the highest temperatures and sea levels of the Cretaceous, within lowermost Kanguk strata on Axel Heiberg and Ellef Ringnes Islands. Aptian to Santonian foraminiferal biostratigraphy and paleoenvironmental conditions have also recently been refined. This project aims to refine Arctic foraminiferal biostratigraphy for the entire Late Cretaceous and to document spatial and temporal changes in paleoenvironmental conditions using a multi-proxy approach. A transect comprised of two sections on Ellesmere Island are analyzed for relative abundance, morphotypes, diversity, and size of benthic foraminifera. These parameters are compared to chemostratigraphy (?¹³C), bulk rock geochemistry (ICP-MS), and lithologic changes to understand how faunal assemblages and lifestyle changes correlate to the varying paleo-redox conditions of the Polar Sea. Foraminiferal assemblages at both localities are mainly agglutinated taxa with minute test sizes as potential response to oxygen-limited benthic conditions. Under periods of high organic carbon content, assemblages are dominated by the epifaunal genus Trochammina, while lower organic content promotes a more diverse assemblage with infaunal and epifaunal taxa. At the base of the more marginal section, the foraminiferal assemblage indicates a Turonian age and foraminiferal communities have fully recovered from OAE 2. Carbon isotope data at the marginal locality also indicate that OAE 2 lies within the underlying Hassel Formation, documenting diachroneity in the lower Kanguk boundary. OAE 3 is potentially recorded for the first time in the Canadian Arctic, marked by faunal loss and a positive ?¹³C excursion. Foraminiferal species common to Alaska, the Beaufort-Mackenzie region, and the Western Interior Sea in the Kanguk Formation allow for regional correlations. This research contributes to the understanding of the paleoenvironmental and paleoceanographic response to the complex late Cretaceous greenhouse climate in the polar region. Furthermore, detailed biostratigraphic and chemostratigraphic correlations linking the Arctic region to lower latitudes can also be used in future petroleum exploration.