古气候记录的时间标尺及相位关系计算──以塔吉克斯坦Chashmanigar黄土剖面为例

CALCULATIONS OF TIME SCALE FOR PALEOCLIMATE RECORDS AND PHASING RELATIONSHIP BETWEEN DIFFERENT CLIMATE-PROXY TIME SERIES: A CASE STUDY OF CHASHMANIGAR LOESS-SOIL SECTION, TADZHIKISTAN

轨道调谐法是确定第四纪地层时间标尺的主要手段，但人工进行轨道调谐确定时间标尺具有可操作性差、客观性差、工作量大及很难得到最佳结果等缺陷，本文描述了利用计算机自动进行轨道调谐以厘定古气候记录时间标尺的方法步骤。对于不同的气候替代性指标时间序列之间在主要周期频率上的相位关系，作者提出了利用演化凝聚函数法进行计算的新方法。作为实例，利用上述方法对塔吉克斯坦Ｃｈａｓｈｍａｎｉｇａｒ黄土记录进行了时间标尺和相位关系演化的计算。

Most of the classic orbital tuning methods developed so far need visual judgements to add new time control points into the climatic records, thus being time-consuming and hindering the construction of high resolution climatic time series. In this paper, an automatic orbital tuning method was described, with which, additional time control points can be automatically added into the climatic records, and a 'best' age for each of the climatic data can be calculated. As a case study, a time scale of Chashmanigar loess-soil section, Tadzhilkistan was established by the automatic orbital tuning method using median grain size data as the climatic-proxy. In this case study, the correlation coefficients between the filtered 41 000a component and the obliquity curve and between the filtered 21 000a component and the precession (both coefficients also served as the criterion of the fitness of tuned climatic time series with target curves), are 0.915 0 and 0.923 9 respectively. It turns out that the automatic orbital tuning method can lead to a very good agreement of climatic time series with theoretical changes in the orbital elements. As a new assessment method of phase differences between different climatic-proxy time series on major period frequencies, the evaluative coherency analysis method is proposed. Phase differences between magnetic susceptibility and median grain size and between red-color reflectance and median grain size from Chashmanigar section, Tadzhikistan on the periods of 41 000a, 23 000a and 19 000a are calculated. The results show that these phasing relationships are different in different time span and on the different frequency. However, the climatic significance of these phasing relationships need to be explored further.