Abstract

Analyses of 87Sr/86Sr in foraminifera and sedimentological observations suggest that the Chicxulub impact was not the trigger for slumps or a hiatus within the Maastrichtian section recovered at Ocean Drilling Program Sites 1049, 1050, and 1052 (subtropical western North Atlantic). The slumps and hiatus occur within a sequence dominated by pelagic chalk. The 87Sr/86Sr measurements show a general increase through the Maastrichtian at each site, but suggest chronostratigraphic gaps on the order of 106 yr across the slumps. Some of the slumps have burrowed upper surfaces and are composed of material that is older and coarser grained than the bounding chalks. Pelagic deposition punctuated by gravity flows easily explains the Maastrichtian record on Blake Nose, whereas an impact-based explanation for slumping is difficult to reconcile with sedimentological and geochemical observations.

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