Sr stratigraphy and biostratigraphy for samples from DSDP Hole 32-305 and ODP Hole 123-766A

The strontium isotope ratios (87Sr/86Sr) of marine barite microcrystals separated from Cretaceous sedimentary deposits from Ocean Drilling Program and Deep Sea Drilling Project sites from the Pacific and Indian Oceans have been compared to the composite Sr isotope curve of McArthur et al. The barite in these cores accurately recorded the seawater 87Sr/86Sr ratio, thereby reaffirming the composite Cretaceous strontium curve. Moreover, marine barite is a more reliable recorder of 87Sr/86Sr than is carbonate in sedimentary deposits with high clay content, thereby providing an opportunity for Sr isotope stratigraphy and dating in carbonate-poor or diagenetically altered sections. We have used the barite-derived Sr isotope record to refine the biostratigraphic age models of the sites investigated.本研究将从太平洋及印度洋海域大洋钻探计划（Ocean Drilling Program）与深海钻探计划（Deep Sea Drilling Project）站位的白垩纪沉积地层中分离得到的海洋重晶石微晶体的锶同位素比值（87Sr/86Sr），与McArthur等人提出的锶同位素综合曲线进行对比分析。上述岩心中的重晶石可准确记录海水87Sr/86Sr比值，由此进一步验证了白垩纪锶同位素综合曲线的可靠性。此外，在黏土含量较高的沉积地层中，海洋重晶石作为87Sr/86Sr比值的记录载体，其可靠性优于碳酸盐岩，这为贫碳酸盐岩地层或成岩蚀变剖面的锶同位素地层学研究与年代测定提供了可行途径。我们依托重晶石获取的锶同位素记录，对本次研究所涉及站位的生物地层年龄模型进行了优化修正。