A LATE CRETACEOUS CHRONOLOGY OF LARGE, RAPID SEA-LEVEL CHANGES: GLACIOEUSTASY DURING THE GREENHOUSE WORLD

Drilling by ODP Leg 174AX provided a record of 12-15 Upper Cretaceous sequences in the New Jersey (NJ) Coastal Plain that provides the basis for reconstructing the timing and amplitude of sea-level variations; integration of Sr-isotopic and bio- stratigraphy provides a chronology for these sequences with a resolution of ~±0.5 m.y. We provide a backstripped Late Cretaceous sea-level record using these sequences, taking into account sediment loading, compaction, paleo-water depth, and basin subsidence. Here we show that sea-level changes were large (>25 m) and rapid (<<1 m.y.), strongly suggesting a glacioeustatic control of sea-level variations during the Late Cretaceous. The NJ Late Cretaceous sequence boundaries generally correspond in age with sea-level lowerings of Exxon Production Research (EPR), NW European and Russian sections, indicating a global cause, though previous EPR amplitudes are too large by a factor of 2. Oxygen isotopic data, a proxy for ice volume and paleotemperatures, are consistent with a glacioeustatic cause. Comparison of sea-level records with other changes in the geobiosphere (e.g., extinctions, adaptive radiations, ocean anoxic events, carbon isotopic variations) show that long-term (10-m.y.-scale) sea-level changes are associated with the general diversification of Mesozoic phytoplankton, but there is little correlation on the m.y.-scale.