Time Series Fractal Compar ison and Its Sign if icance of the Gra in-Size Fractal Dimensions and Climatic Proxy from Core 69 in the Eastern South China Sea
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摘要: 南海69柱粒度数据分析表明,晚更新世以来,粒度在0.2~11μm的标度范围内具有分形特征,粒度分维值DS为1.72~2.02,平均1.84;不同时期粒度分维值明显不同,氧同位素1期(冰后期)为1.88,氧同位素2期(冰期)为1.81,温暖的冰后期粒度分维值高且变化幅度大,寒冷的冰期粒度分维值低且变化幅度小,表明粒度分维值DS对沉积物的形成环境演化具有良好的指示意义。运用R/S分析法,对69柱沉积物的粒度分维值DS、UK37法估算的表层海水古温度、浮游有孔虫的δ18O、δ13C及其转换函数计算的冬季表层海水古温度、夏季表层海水古温度、季节性温差、沉积物SiO2、CaCO3含量9项指标进行尺度重整分析计算,得到其时间序列分维值DH分别为1.2855、1.1712、1.2659、1.4244、1.2719、1.2214、1.2979、1.1366、1.1609。虽然这些气候指标是用不同物理单位测量的,但运用分形分析可以对它们进行数学比较,粒度分维值DS与季节性温差二者的时间序列分维值DH最接近,从分形理论方面进一步证实粒度分维值DS的变化主要反映气候的冷暖变化。综合粒度分维值DS及其他气候代用指标分析,识别出南海东部全新世以来的4次突发事件。Abstract: The grain size of samp les from sediment Core 69 in the Eastern South China Sea has been measured.Based on the fractal theory, the fractal dimension (DS) of the grain-size has been calculated. Results show that the grain - size distribution has fractal characteristics. Since late Pleistocene, the DS values of Core 69 in the Eastern South China Sea are 1.72-2.20,with an average of 1.84, Meanwhile, the DS values are different from the same core in the glacial and post glacial stage. The DS value is 1.88 and its variation is frequent during stage 1 of the oxygen isotope stratigraphy. The DS value is 1.81 and its variation is infrequent during stage 2 of the oxygen isotope stratigraphy. That is , the high value ofDS is related to the high paleotemperature but the low value of DS is related to the low paleotemperature. The fractal dimension (DS) of grain-size is considered as an important proxy describing paleoenvironment variations recorded from sediments. R /S analysis on the curves of the fractal dimension of the grain-size , paleotemperature of Uk37 values, δ18O ratios andδ13 C ratios , sea surface temperature in winter and summer, seasonal variability of sea surface temperature between winter and summer, CaCO3 content and SiO2 content yields time series fractal dimensions (DH) of 1.2855, 1.1712, 1.2659, 1.4244, 1.2719, 1.2214, 1.2979, 1.1366, 1.1609 respectively. Although these climatic data were measured in different physical units and different time scales, fractal analysis allows for a mathematical comparison of them. Among them , the time series fractal dimension of seasonal variability of sea surface temperature is close to that of the fractal dimensions of grain-size. These show that the fractal dimensions of grain-size reveal climatic variability. Based on the grain-size fractal dimensions and climatic proxy, four abrupt climate events have been revealed during the Holocene.
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Key words:
- the Eastern South China Sea /
- grain size /
- R /S analysis /
- fractal comparison
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