NSFGEO-NERC: Developing A New Lower Cretaceous Time Scale: Foundation For The Next Generation Of Paleoceanographic And Biogeochemical Studies

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During unusually warm greenhouse conditions of the Aptian to Cenomanian, several major perturbationsin the global carbon cycle are reflected by black shale deposits and/or carbon isotope excursions (OAEs).To fully understand the ocean-climate dynamics of this greenhouse world, and the mechanistic driversthat propel ocean anoxia and deterioration of ecosystems, new radioisotopic dating, in parallel with amore geographically dispersed array of high-quality Cretaceous sedimentary records are essential. TheYezo Group (YG), Japan comprises Aptian to Maastrichtian sediment deposited in a high latitude PacificOcean-facing fore arc basin. Unlike other well-studied Lower Cretaceous sequences, e.g., the VocontianBasin, France (VB), the YG contains rhyolitic tuffs amenable to precise U-Pb and 40Ar/39Ar dating. Wepropose to obtain new radioisotopic dates from the YG in concert with new osmium (Os) and carbon (C)isotope chemostratigraphy. This new chronology and chemostratigraphy can be exported and correlated torecords from Tethys, including the VB for which we aim to generate new Os and C isotopechemostratigraphy and an astrochronologic age model focused on the critical onset interval of OAE1a.Our proposed research to update and improve the Lower Cretaceous time scale by integrating French andJapanese strata is designed to rectify critical time scale inaccuracies, and employ refined time scales andnew proxy data to address fundamental questions concerning lithosphere-hydrosphere-biosphereinteractions associated with major Cretaceous C-cycle perturbations such as OAEs.