Paleopedology, palynology, and geochronological interpretation of alluvial paleosols, Cenomanian Dunvegan formation, Alberta, Canada

Abstract

The Dunvegan Formation is a mid-Cretaceous deltaic deposit exposed in the Rocky Mountain foothills of Alberta and British Columbia along the Peace River Valley. Intrinsic features of Dunvegan Formation paleosols understood through micromorphology, geochemical, and mineralogical analysis provide a paleoclimatic interpretation of warm to cool temperate. Micromorphological and geochemical analysis lead to reconstruction of the depositional and pedogenic histories of the five primary paleosols of this study. Preserved palynomorphs of the paleosols are primarily composed of fern spores with much less abundant conifer and cycad species. The paleoclimate based on the palynomorphs is humid and ranges from cool temperate to subtropical. The overall paleoenvironmental interpretation based on both paleosols and palynology is humid cool to warm temperate. Geochronology using the ⁴⁰Ar/³⁹Ar dating method was implemented in an effort to date pedogenesis. This technique needs further refinement in order to be successful in dating paleosols. The multi-proxy approach of this study lead to a more complete interpretation of the climatic, pedogenic and depositional history and should be used in the future.