Cretaceous Paleoenvironmental History of the Sverdrup Basin: a Multi-Fossil, Geochemical and Carbon Isotope Stratigraphic Approach

Claudia Schroder-Adams

This study addresses Cretaceous strata in the Sverdrup, Anderson and Mackenzie basins by taking a multidisciplinary approach to refine stratigraphic correlations and paleoenvironmental interpretations and as such permit integration of the Boreal Realm into global climatic trends and sea-level histories. Our localities contrast deep basin with shelf settings identifying different paleoenvironments and taphonomic regimes. New insights in the paleoenvironmentally- and burial history-driven taphonomy of existing faunal and floral assemblages necessitate a multi-fossil approach for successful biostratigraphic analysis. Observed transgressive-regressive cycles are likely linked to expansion and retraction of oceanic oxygen minimum zones and in turn affect dinoflagellate and radiolarian assemblage compositions. Deep-water fauna such as benthic foraminiferal communities are severely restricted by bottom water hypoxia particularly during the early Late Cretaceous global temperature maximum, Oceanic Anoxic Event II and sea-level highstand. A newly established carbon isotope record of nearly the entire Cretaceous succession as exposed on Axel Heiberg Island documents several positive and negative δ13Corg excursions. These excursions tie well to precisely dated European low latitude carbon isotope records, bringing an unprecedented stratigraphic accuracy to the Boreal Sea strata. Emerging microfossil zonations utilizing foraminifera, diatoms, radiolarians and dinoflagellates can now be calibrated on a much finer scale. For example, the first radiolarian zonation for the Upper Cretaceous Kanguk Formation of the Sverdrup Basin is proposed. Calibrations of marine paleoproductivity events as reflected in pelagic assemblages and carbon burial rates throughout the Turonian to Santonian suggests a strong effect of global sea-level trends on the Arctic basins studied here, in contrast to changes in lithospheric stresses as previously suggested. Accelerated tectonic activity during the Cretaceous resulted in high frequency ashfalls that influenced paleoproductivity and the taphonomy of siliceous assemblages. Geochemical fingerprinting of these bentonites permits their correlation across the vast Arctic region. Bentonites also provide a new geochronological framework tying in with established biozones.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013