Stable isotope record and age determination of ODP Site 121-758 in the northeastern Indian Ocean

Numerous studies have shown that delta18O records from benthic and planktonic foraminifera, primarily a proxy of global ice volume variations, reflect Milankovitch periodicities. To study climatic response to orbital forcing at Ocean Drilling Program site 758, we have generated continuous delta18O and delta13C records from a single benthic foraminiferal species Cibicides wuellerstorfi for the last 3.6 m.y. and extended the planktonic foraminiferal isotope records of Farrell and Janecek (1991, doi:10.2973/odp.proc.sr.121.124.1991) (0-2.5 Ma, based on Globigerinoides sacculifer) to 3.6 Ma (Chen, 1994). We then constructed an age model by matching, correlating and tuning the benthic delta18O record to a model simulation of ice volume (Imbrie and Imbrie, 1980, doi:10.1126/science.207.4434.943). The filtered 41- and 23-kyr signals based on the resultant astronomically tuned age model are highly correlated to obliquity (r=0.83) and precession (r=0.75), respectively. […]

众多研究业已表明，来自底栖及浮游有孔虫的delta18O记录，主要作为全球冰量变化的代用指标，反映了米兰科维奇周期性。为探究对海洋钻探计划758号站点的轨道强迫的气候响应，我们已从单一的底栖有孔虫物种Cibicides wuellerstorfi中生成连续的delta18O和delta13C记录，时间跨度为过去3.6百万年，并扩展了Farrell和Janecek（1991年，参考文献号：10.2973/odp.proc.sr.121.124.1991）所记录的浮游有孔虫同位素数据（基于Globigerinoides sacculifer，0-2.5百万年）至3.6百万年（Chen，1994年）。随后，通过将底栖delta18O记录与冰量模型模拟（Imbrie和Imbrie，1980年，参考文献号：10.1126/science.207.4434.943）进行匹配、相关性分析和调整，构建了一个年龄模型。基于所得天文调谐年龄模型的过滤后的41和23千年的信号与倾斜度（相关系数r=0.83）和岁差（相关系数r=0.75）高度相关。