High-Latitude Depositional Systems, Provenance, and Basinal Setting of the Late Cretaceous Cantwell Basin, Denali National Park and Preserve, Alaska: A Stratigraphic Framework for Paleontological and Paleoclimatic Studies

Abstract

The Cantwell Formation of the central Alaska Range provides a robust archive of high-latitude, Late Cretaceous depositional systems and paleo-floral/faunal assemblages. Our stratigraphic analysis defines two mappable members. The lower member (1500–2000 m thick) represents vegetated alluvial fan and braided fluvial systems that transition up-section to fluvial–estuarine systems that drained into an inland continental seaway. The upper member (~2000 m thick) represents estuarine–marginal marine and lacustrine systems. Previous paleontological studies demonstrate that the Cantwell basin was populated by various dinosaurs, fishes, bivalves, birds, and marginal marine micro-organisms. Integration of new and published geologic mapping allows for reconstruction of depositional systems at the basin scale and provides additional paleogeographic context. The northern basin margin was defined by a previously unrecognized south-verging thrust belt, whereas the southern margin of the basin was defined by a north-verging thrust belt inboard of an active magmatic arc. Sediment sources interpreted from U-Pb detrital zircon geochronology included the coeval magmatic arc and older Cretaceous plutons, and Proterozoic–Mesozoic strata exhumed along the basin margins. Results of our study provide a depositional, stratigraphic, and structural framework that may serve as a guide for future paleontological and paleoclimatic investigations of Late Cretaceous Arctic environments of the Cantwell basin.