Testing the isochrony, estimating the rates and tracking the beat of early Late Cretaceous sea-level changes: an integrated interplate approach.

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The warm early Late Cretaceous greenhouse epoch was characterized by generally rising or high sea-level stands repeatedly punctuated by large and rapid sea-level drops, the reasons of which are still poorly understood. Some of the sea-level falls have been speculated as glacio-eustatically driven by means of positive δ18O shifts in more-or-less diagenetically unaltered foraminiferal calcite from ODP legs. However, the isotopic evidence is often ambiguous and offshore core logs and onshore sequences are still difficult to correlate. On the other hand, onshore sequences bear much more comprehensive information on, and have significant potential for unravelling the pattern of early Late Cretaceous sea-level change. Unconformities are well expressed onshore and they can be stratigraphically calibrated by means of integrated approaches, especially high-resolution macrofossil biostratigraphy, carbon stable isotopes and cyclostratigraphy. Along with analyses of (bio-)facies and stratal architectures such as on-/offlap geometries or incision at sequence boundaries, a fairly precise assessment of the magnitudes and rates of sea-level change is possible. In order to test the isochrony of early Late Cretaceous sea-level change, an interplate sequence stratigraphic study of selected Cenomanian-Turonian (~100-90 myr) sea-level events on different tectonic plates (Europe, northern Africa, Middle East) is proposed. Furthermore, the periodicities of the sea-level changes and the role of highfrequency orbital forcing in the Milankovitch Band (<500 kyr) versus low-frequency modulation of these oszillations (>1 myr) will be estimated. This study will be a crucial test for reconstructions based on isotope proxies only, and bears important implications for both Mesozoic greenhouse climates and the evaluation of future sea-level change.