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

支持者将进一步测试和开发一种流动分析技术，用于测定浮游有孔虫中的Mg/Ca，这是海洋表面温度（SST）的代表。在有孔虫的大量溶解样品中测量Mg/Ca的一个问题是，溶解会使Mg/Ca分离。此外，后期的钙化和污染相会使Mg/Ca信号复杂化。使用ICPMS和时间分辨分析（TRA）的清洗技术，可以在有孔虫缓慢溶解和分析时监测Mg/Ca信号。该技术与用于40Ar/39Ar测年的逐步加热原理相似，有望区分最靠近地表形成的早期方解石和其他不需要的信号。对科科斯岭~900米和~2000米处采集的两个岩心样本进行的初步研究显示出有希望的初步结果。对制备的G. ruber和G. sugllifer样品的TRA分析显示，Mg/Ca的初始值较高，被认为是初始形成的方解石。该技术将对其他样品进行更多的校准，与Mn含量和d18O进行比较。最后，将利用该技术对热带和亚热带太平洋冰芯的末次盛冰期海温进行地图和时间序列分析，以解决热带在气候变化中的作用的争议。

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.