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.

支持者将通过分析技术进一步测试和发展流动，以确定浮游物孔中的mg/ca，这是海面温度（SST）的代理。在大量溶解的有孔样品中测得的mg/ca的问题是，溶解可以分割mg/ca。此外，后来的钙化和污染物相可能使MG/CA信号复杂化。使用ICPM和时间分辨分析（TRA）的清洁技术流动，随着孔的缓慢溶解和分析，将允许监测MG/CA信号。该技术原则上与用于40AR/39AR约会的逐步加热相似，并有望区分最接近表面和其他不需要信号的早期方解石。对Cocos Ridge的两个核心的样品的试点研究显示出令人鼓舞的早期结果。对G. ruber和G. acculifer的样品的TRA分析显示，Mg/Ca的高初始值被认为是最初形成的方解石。对于其他样品，将对该技术进行更多的校准，并与MN含量和D18O进行比较。最后，新技术将用于分析地图和时间序列中的SST回到热带和亚热带太平洋的核心的最后一个冰川最大值（LGM），以解决有关热带在气候变化中的作用的争议。