(Table 3) Relative depth and age, CaCO3, δ¹⁸O, δ¹³C and Sr/Ca analysis from ODP Leg 130, 154 and 138

Interpretations of calcite strontium/calcium records in terms of ocean history and calcite diagenesis require distinguishing the effects on deep-sea calcite sediments of changes in ocean chemistry, of different mixes of calcite-depositing organisms as sediment contributors through time and space, and of the loss of Sr during diagenetic calcite recrystallization. In this paper Sr/Ca and d18O values of bulk calcium carbonate sediments are used to estimate the relative extent of calcite recrystallization in samples from four time points (core tops, 5.6, 9.4, and 37.1 Ma) at eight Ocean Drilling Program sites in the equatorial Atlantic (Ceara Rise) and equatorial Pacific (Ontong Java Plateau and two eastern equatorial Pacific sites). The possibility that site-to-site differences in calcite Sr/Ca at a given time point originated from temporal variations in ocean chemistry was eliminated by careful age control of samples for each time point, with sample ages differing by less than the oceanic residence times of Sr and Ca. The Sr/Ca and d18O values of 5.6- and 9.4-Ma samples from the less-carbonate-rich eastern equatorial Pacific sites and Ceara Rise Site 929 appear to be less diagenetically altered than the Sr/Ca and d18O values of contemporaneous samples from the more carbonate-rich sites. It is evident from these data that both Sr/Ca and d18O in bulk calcite have been diagenetically altered in some samples 5.6 Ma and older. These data indicate that noncarbonate sedimentary components, like clay and biogenic silica, have partially suppressed recrystallization at the lower carbonate sites. Sr/Ca data from the less altered, carbonate-poor sites indicate higher oceanic Sr/Ca relative to today at 5.6 and 9.4 Ma.

针对方解石锶钙（Sr/Ca）记录的海洋历史与方解石成岩作用开展解译时，需区分三类对深海方解石沉积物产生影响的因素：海洋化学变化、随时间与空间变化的方解石沉积生物贡献组合差异，以及成岩作用中方解石重结晶过程中的锶流失效应。本文采用全岩碳酸钙沉积物的Sr/Ca比值与氧同位素δ¹⁸O值，估算赤道大西洋（塞阿拉海隆）与赤道太平洋（翁通爪哇海台及2个东赤道太平洋站位）8个大洋钻探计划（Ocean Drilling Program）站位的4个时间节点（岩心顶部、5.6 Ma、9.4 Ma及37.1 Ma）的样品中方解石重结晶的相对程度。通过对每个时间节点的样品进行严格的年代控制（样品年龄差小于锶与钙的海洋停留时间），排除了特定时间节点内不同站位间方解石Sr/Ca比值差异源于海洋化学随时间变化的可能性。相较于同期高碳酸盐丰度站位的样品，东赤道太平洋低碳酸盐丰度站位与塞阿拉海隆929站位的5.6 Ma和9.4 Ma样品，其Sr/Ca比值与δ¹⁸O值的成岩蚀变程度更低。由本研究数据可知，5.6 Ma及更老的部分样品中，全岩方解石的Sr/Ca比值与δ¹⁸O值均发生了成岩蚀变。上述数据表明，在低碳酸盐丰度站位中，黏土与生物硅等非碳酸盐沉积组分部分抑制了方解石重结晶作用。来自蚀变程度更低的低碳酸盐丰度站位的Sr/Ca数据显示，5.6 Ma与9.4 Ma时的海洋Sr/Ca比值较现代更高。