SGER: Direct Calibration of the Time Scale of Global Climatic Change

这一试点项目将尝试获取从临界水平到大洋钻探计划钻芯(758号场地)的精确放射性年龄。长石矿物颗粒将从18个不同的火山灰岩层中分离出来，然后用激光40Ar/39Ar测年技术进行分析。这种方法具有前所未有的灵敏度和精确度，如果能从这些火山层中提取合适的物质，就可以获得精度在几千年内的年龄。由于这个岩心是用氧同位素和古地磁方法研究的，所以所得到的时间尺度可以精确地校准过去500万年的整个磁学和全球气候变化年代学。氧同位素比值变化的理论预期周期与标准磁反转时间尺度之间的偏差已经引起了对其准确性的严重质疑。激光40Ar/39Ar测年可能是解决这些问题的最大潜力。然而，该项目是“高风险”的，因为目前还不知道是否可以从消耗臭氧潜能值岩芯中获得足够的可测定日期的材料。如果成功，该项目不仅可以改善目前公认的全球气候变化的时间尺度，而且还有可能估计地球对地球气候系统的天文输入的响应率。

This pilot project will attempt obtain precise radiometric ages from critical levels to of an Ocean Drilling Program drill core (site 758). Feldspar mineral grains will be separated from 18 different volcanic tephra layers and then subjected to analysis using the laser 40Ar/39Ar dating technique. This method has unprecedented sensitivity and precision, and if suitable material can be extracted from these volcanic horizons, ages with accuracies to within a few thousand years can be obtained. Since this core been studied using oxygen isotopic and paleomagnetic methods, the time-scale derived could precisely calibrate the entire magnetic and global climate change chronology over the past 5 million years. Divergences between the theoretically expected periodicities of oxygen isotope ratio variations and the standard magnetic reversal time scale have raised serious questions about its accuracy. Laser 40Ar/39Ar dating has probably the greatest potential for resolving these questions. However, the project is 'high-risk' in the sense that is not yet known if sufficient datable material can be obtained from ODP cores. If successful, this project could not only improve the currently accepted time scale of global climatic change, it also has the potential for being able to estimate the response rate of the earth to the now well-established astronomical inputs to the earth's climate system.