Refining Mg/Ca paleothermometry in foraminifera: Overcoming the dissolution problem with a flow-through leaching procedure

精炼有孔虫中的 Mg/Ca 古测温法：通过流通浸出程序克服溶解问题

• 批准号: 0136905
• 负责人: Gary Klinkhammer
• 金额: $ 34.34万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-02-15 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0136905&HistoricalAwards=false
• 关键词: Refining; Mg; Ca; paleothermometry; foraminifera

The proponents will further test and develop a flow through analytical technique for the determination of Mg/Ca in planktonic forams, a proxy for sea surface temperature (SST). A problem with measured Mg/Ca in bulk dissolved samples of forams, is that dissolution can fractionate Mg/Ca. In addition, later calcification and contaminant phases can complicate the Mg/Ca signal. The flow through cleaning technique, using the ICPMS and time-resolved analysis (TRA), will allow monitoring of the Mg/Ca signal as the forams are slowly dissolved and analyzed. This technique is similar in principle to stepwise heating used for 40Ar/39Ar dating and is expected to distinguish between the early calcite formed nearest the surface and other unwanted signals. A pilot study of samples from two cores taken at ~900m and ~2000 at the Cocos Ridge show promising early results. TRA analysis of prepared samples of G. ruber, and G. sacculifer show high initial values of Mg/Ca thought to be the initially formed calcite. More calibration of the technique will be done for other samples, with comparisons to Mn contents and d18O. Finally, the new technique will be used to analyze SST in map and time-series back to the Last Glacial Maximum (LGM) in cores from the tropical and subtropical Pacific to resolve controversy about the role of the tropics in climate change.

提议者将进一步测试和开发一种流通分析技术，用于确定浮游有孔虫中的镁/钙，这是海洋表面温度的一个代用指标。有孔虫的大量溶解样品中测量的Mg/Ca的问题在于溶解可使Mg/Ca破碎。此外，后期的钙化和污染阶段会使Mg/Ca信号复杂化。使用ICPMS和时间分辨分析（TRA）的流通清洁技术将允许在有孔虫缓慢溶解和分析时监测Mg/Ca信号。这种技术在原理上类似于用于40 Ar/39 Ar测年的逐步加热，并有望区分最接近地表的早期方解石和其他不需要的信号。对在科科斯海脊约900米和约2000米处采集的两个岩心样品进行的初步研究显示出有希望的早期结果。对G. ruber，和G. sacculifer显示高初始值的Mg/Ca被认为是最初形成的方解石。将对其他样品进行更多的技术校准，并与Mn含量和d18 O进行比较。最后，新技术将被用来分析SST的地图和时间序列回到末次冰期最大值（LGM）的核心从热带和亚热带太平洋，以解决争议的热带气候变化中的作用。