Strontium isotope profiles across K/T boundary sequences in Denmark and Antarctica

Strontium isotope profiles, derived from minimally altered samples, across marine K/T boundary sequences exposed at Kjّlby Gaard and Nye Klّv, Denmark, and on Seymour Island, Antarctica, show neither the boundary excursions, nor the boundary spikes, in 87Sr/86Sr that have been reported for K/T boundary sequences from elsewhere. Nor do our data conform to modelled predictions of the Sr isotopic response of the oceans to a positive spike in 87Sr/86Sr at the terminal Cretaceous. Boundary values for 87Sr/86Sr (with 95% confidence intervals) are 0.707828±3 in Denmark and 0.707832±7 in Antarctica. Our data suggest that 87Sr/86Sr stopped increasing and started decreasing at least 90 ka before the K/T boundary.