--> The Canadian Cretaceous Polar and Western Interior Seas: Paleoenvironmental History and Paleoceanographic Linkages

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The Canadian Cretaceous Polar and Western Interior Seas: Paleoenvironmental History and Paleoceanographic Linkages

Abstract

This study reviews the Cretaceous history of the Polar and Western Interior seas as recorded in the Canadian High Arctic Sverdrup Basin, Beaufort-Mackenzie Basin of northwest Canada and Western Canadian Foreland Basin. As such we discuss large-scale Cretaceous environmental perturbations by contrasting shared basin responses and their controls with those distinct to individual basins. Newly emerging stratigraphic, paleoclimatic and paleoenvironmental interpretations from the polar realm allow for a fresh look at the response of this unique oceanic system to global climatic trends and sea-level history over 60 Ma. Sverdrup Basin localities on Ellesmere, Axel Heiberg and Ellef Ringnes islands represent shelf to slope environments that contrasted with the shallow water and low gradient settings of the Canadian Western Interior Sea. Both marine systems, connected throughout the Aptian to Maastrichtian, responded to global transgressive-regressive cycles resulting in dynamic paleogeographic changes. The shallow basin setting and in particular the forebulge and backbulge settings of the Western Canadian Foreland Basin are characterized by multiple erosional surfaces throughout the Cretaceous succession. The upper Albian disconformity is widely discernible and might have left a short-lived northern closure of the latest Albian Mowry Sea that may have been responsible for the large loss of benthic foraminiferal species at this time. Several oceanic anoxic events are documented in these basins representing their response to global climate dynamics and perturbations of the carbon cycle. Carbon isotope stratigraphy allows for improved biostratigraphic and paleoenvironmental event correlations between these basins. Mechanisms of watermass stratification and bottom water oxygenation are explored as well as the influence of the High Arctic Large Igneous Province on Polar ecosystems. The Canadian Western Interior Sea biotic communities were controlled by watermasses of two or maybe three different sources and physical properties including the Polar, Tethyan and a possibly third source from the emerging Labrador Sea through the Hudson Seaway. Migration of Tethyan-derived calcareous phyto- and zooplankton were controlled by temperature and salinity gradients and did not invade northern regions. Siliceous plankton occurred more commonly in the Sverdrup Basin. This talk reviews the big picture by linking basin records to the dynamic processes of Cretaceous time.