STRONTIUM ISOTOPIC EVIDENCE FOR EXTENSIVE REWORKING IN SEDIMENTS SPANNING THE CRETACEOUS-TERTIARY BOUNDARY AT ODP SITE-738

The Maastrichtian and Danian intervals of Ocean Drilling Program (ODP) Hole 738C contain numerous microfossils above the level of their puta tive extinction, suggesting either (1) persistence of local communitie s long after species turnover occurred across the rest of the globe or (2) large-scale reworking. These interpretations have very different paleoenvironmental implications, but discriminating between them has p roved difficult. To test the competing hypotheses, we measured the Sr- 87/Sr-86 ratios of taxon-specific separates from a number of samples a nd compared these values both to each other and to expected seawater v alues at the time of deposition. Our results indicate extensive and pe rvasive reworking throughout Maastrichtian and lower Danian strata in ODP Hole 738C. We estimate that up to 30% of the mass of foraminifers in any sample can be contributed by individuals that have been reworke d.