Foraminiferal biostratigraphy and paleoenvironments of the Cretaceous Colorado group in southeastern and east central Alberta, Canada

The Colorado Group in the Western Canada Sedimentary Basin is a shale-dominated interval that documents a complex history of the Cretaceous Western Interior Sea. Foraminiferal assemblages play a crucial role in interpreting paleoenvironments closely linked to sea-level changes and anoxic events. This study is based on three reference cores that document deposition and biotic changes from the Latest Albian Westgate Formation to the Santonian Niobrara Formation in southeastern and east central Alberta. The interval covers the Greenhorn and Niobrara sea-level cycles that have resulted in major paleogeographic changes of North America.; The regression of the Greenhorn cycle and severe constriction of the seaway is documented in the Upper Turonian Carlile Formation with the return to agglutinated assemblages. Renewed transgression deposited the Niobrara Formation with mixed agglutinated/calcareous benthic and planktic faunas. Subtle faunal changes resulted in a refined subzonation. Morphogroups of benthic and planktic foraminifera and their vertical and lateral compositional changes deliver important information on paleoecological change. (Abstract shortened by UMI.)...