Recent Advances in Late Cretaceous Geochronology and Chronostratigraphy

The sedimentary record has commonly been interpreted as riddled with hiatuses, perhaps recording as little as a tenth of elapsed geologic time in any given succession. In the past, when radioisotopic dates were widely spaced... [ view full abstract ]

The sedimentary record has commonly been interpreted as riddled with hiatuses, perhaps recording as little as a tenth of elapsed geologic time in any given succession. In the past, when radioisotopic dates were widely spaced and their uncertainties large, there was little to challenge such conventional wisdom, save for the ranting of cyclostratigraphers whose ability to distill evidence of Milankovitch periodicities from some successions seemed to suggest a higher level of stratigraphic completeness. Recent advances in the integration of geochronology, astrochronology, biostratigraphy, and chemostratigraphy for Late Cretaceous sections of the Western Interior basin and other areas have made it possible to more rigorously evaluate stratigraphic completeness in the process of refining geologic time scales. The application of independent chronometers (U-Pb, Ar-Ar, and floating astrochronologies) has allowed for significant advances in accuracy, precision and confidence in the resulting time scales, while helping to validate claims for the preservation of orbital signals in hemipelagic strata. New methods developed in the course of this research include not only advances in analytical approaches to geochronologic determinations, but also more comprehensive assessments of total uncertainties associated with time scale development. Lastly, the use of chemostratigraphic frameworks to help export refined temporal control to areas where either biostratigraphy and/or datable horizons are lacking, has enormous potential to extend and refine global Cretaceous chronostratigraphy. The talk will summarize these recent developments.