Evidence for a small (similar to 0.000030) but resolvable increase in seawater Sr-87/Sr-86 ratios across the Cretaceous-Tertiary boundary

Previous studies of Sr-87/Sr-86 patterns across the Cretaceous-Tertiary (K- T) boundary have generated inconsistent results. Analyses of samples from O cean Drilling Program Hole 1049C provide better taphonomic and diagenetic c ontrol than has been previously achieved and indicate (1) that there was a rapid increase of similar to0.000 030 in seawater Sr-87/Sr-86 ratios across the K-T boundary, (2) that post-K-T Cretaceous foraminifera at this site a re reworked, and (3) that subtle diagenetic overprinting affects the basal similar to 15 cm of the Danian ooze. These conclusions are consistent with the asteroid impact hypothesis. Reworking rather than survivorship confirms nearly complete extinction of Cretaceous Tethyan planktic foraminifera; th e Sr-87/Sr-86 excursion can be explained by enhanced continental weathering , perhaps related to acid rain in the aftermath of the K-T impact.