PALEOCEANOGRAPHIC CONDITIONS OF LATE CRETACEOUS COLORADO GROUP FORMATIONS OF THE WESTERN CANADIAN SEDIMENTARY BASIN, ALBERTA, CANADA

High resolution sampling (every 0.5 m) and description of virtually continuous, slabbed, whole core of Late Cretaceous Middle Colorado Group Formations from the Western Canadian Sedimentary Basin (Alberta) provides a better understanding and evolution of paleoceanographic conditions of the Cretaceous Western Interior Seaway (KWIS) from the Latest Albian to Early Coniacian Ages (~ 10 Ma). Quantitative wavelength dispersive X-ray fluorescence for major oxides and trace elements coupled with stable C & N isotopes and organic richness quantification were used to better constrain and elucidate paleoredox conditions and nutrient dynamics of the KWIS during the studied time interval. Trace metal excursions revealed multiple episodes of euxinia punctuated by oxic to suboxic conditions and further denote the onset and continuation of a major, basin-wide transgression, i.e., the K1 flooding surface and Greenhorn Cyclothem. Notable to the Late Cretaceous Colorado Group is Oceanic Anoxic Event 2 (OAE2) which was identified in the Second White Specks Formation through δ¹³C isotopic analysis of organic matter. The onset of OAE2 correlates with enriched C isotopic values (-26‰ to -24‰ from an average baseline of -26.5‰) and lowered Mo trace metal abundances. The Plenus Cold Event in OAE2 was identified by depleted C isotopic values and elevated Mo trace metal abundances. Frequent oscillations in the δ¹⁵N isotopic values suggest that water column stratification was variable. ~ 1 ‰ δ¹⁵N values suggest denitrification by diazotrophs and values above ~ 2 ‰ suggesting oxygenated conditions were present. Quantification of total organic carbon (TOC) using elemental analysis demonstrates average weight percents of 2% TOC throughout the entire section which may be attributed to maturation of the organic matter beyond the oil window leading to subsequent hydrocarbon migration. Solid state nuclear magnetic resonance on a small number of samples (n = 2) reveals an abundance of bridgehead aryl compounds and coupled with pArC values reveals overmature dry gas conditions.