(Table 1) Oxygen and carbon isotopes and calcium carbonte of bulk carbonate at DSDP Hole 72-516F

A detailed oxygen and carbon isotope study of the upper Maestrichtian-lower Paleocene section of Hole 516F from the Rio Grande Rise reveals that large isotopic anomalies are clearly associated with the Cretaceous/Tertiary boundary. Across the Cretaceous/Tertiary boundary, the total carbonate content reaches a maximum exceeding 80% before rapidly decreasing in covariance with the carbon isotope record. This strong covariance between d13C and percent CaCO3 suggests either a significant reduction in primary productivity or a rapid shoaling of the calcium carbonate compensation depth. Importantly, the d13C record 2 Ma after the Cretaceous/Tertiary boundary remained depleted in 13C by at least 0.5 per mil compared to the late Maestrichtian.