Late Cretaceous to early Tertiary magnetostratigraphy of a continental sequence: Red Deer Valley, Alberta, Canada

Abstract

The Red Deer Valley exposes a conformable 350 m thick late Campanian to Early Paleocene fluvial–deltaic coal-bearing sequence named the Edmonton Group. Systematic sampling and paleomagnetic analysis of the dominant lithologies (mudstones, sandstones, and shales) were carried out over five sections correlated by coal seams to provide some 500 sites (stratigraphic levels). Primary detrital remanent magnetization directions after alternating field cleaning produce a polarity reversal pattern correlatable to sea-floor magnetic anomalies 29–33.The Campanian–Maastrichtian boundary, based upon the first appearance of Wodehouseia, and the Maastrichtian–Paleocene (Cretaceous–Tertiary) boundary, based upon an Ir anomaly associated with dinosaur and Cretaceous palynofloral extinctions, correlate closely magnetostratigraphically with the marine foraminiferal section at Gubbio, Italy. Radiometric dating of bentonites has indicated the ages of these boundaries to be approximately 71 and 64 Ma, respectively.