柴达木盆地钻孔自然伽玛曲线记录的长时段短尺度（千、百年级）古气候变化

【作者】 白世彪；

【导师】 刘泽纯； 陈晔；

【作者基本信息】 南京师范大学 ， 自然地理学， 2002， 硕士

【摘要】 过去全球环境变化过程和机制的研究，对于认识未来气候环境的变化有重要的意义。柴达木盆地第四纪沉积深厚、沉积速率大，分辨率高，有利于提取过去不同层次的古气候变化信息。在涩中6井取芯段(380-1140m)以1-3m不等的间隔采集粒度样品248个；选取关键层位四小段：滨浅湖相(420.3-423.3m)、浅湖相(607.8-609.8m)、浅湖相(926.0-928.9m)和浅湖相(1035-1036.9m)，同步采集样品114个(采样间距10cm)，进行了粒度、粘土矿物、放射性元素(微量元素U和Th及常量元素K)的分析；同时引用四小段陈晔博士论文全岩碳酸盐分析的结果。 涩中6井取芯段具有的良好沉积环境，是利用GR曲线反演千、百年级古气候的基础；关键层位四小段不同的沉积环境中GR值与各古气候指标参数多数都具有很强的相关关系，但相关系数略有差异，因此GR曲线在千、百年尺度的波动同样具有气候意义。 时间标尺的确定是第四纪古气候研究的基础，由于近年来古地磁界限年代经过多次调整，有必要建立新的轨道调谐时间标尺，以便更好地进行全球对比。本文时间标尺引用袁林旺博士论文中最新的轨道调谐的时间标尺，并进一步对GR曲线时间序列进行等间距三次样条函数插值，步长为100年，得到具有千、百年级时间分辨率时间序列GR曲线。 长时段短尺度(千、百年级)气候变化事件是第四纪古气候研究中的薄弱领域。在千、百年尺度上，多种气候代用指标和GR曲线均有很好的匹配关系，可以提取GR曲线上存在的千、百年尺度的古气候信息，讨论千、百年尺度气候事件。 以四小段岩芯的GR曲线为主，综合考虑其他各个指标波动曲线提取GR曲线包含的千、百年的时间尺度的准周期气候变化，得到的几个波动范围在600-800年准周期；又通过统计涩中6井岩芯岩性的变化情况从整体上提取涩中6井GR曲线记录的长时段千、百年古气候周期，得到的1467年准周期；对涩中6井GR曲线时间序列进行等间距三次样条函数插值，步长为100年，相当于10cm的采样间隔，用高通滤波器滤去轨道因数的低频周期，对GR曲线进行谱分析，并对原始谱分析结果进行5点移动平均平滑和对结果进行显著性检验，显示了一系列的千、百年尺度的气候变化准周期；同时通过以上三种方法得到的准周期多数能对应于其它的一些古气候记录的准周期；也进一步证明了我们所发现周期的真实性。更多还原

【Abstract】 To realize more clearly the evolution of climate and environment in the future, it is important to explore and analyze the processes and mechanism of the environment changes in the past. Due to such a high sediment rate in the Qaidam Basin, where exits long and continuous Quaternary sequence, there is a higher resolution to reconstruct the paleoclimatic and paleoenvironmental changes in the Quaternary. This dissertation addresses on the Sezhong 6 core with a length of 760m,located near the center of the Caidam Basin,where 248 samples at a vertical spacing l~3m were firstly collected systematically to analyze the content of grain size . Secondly, the typical 4 short layers are chosen, where 114 samples at an average vertical spacing 10cm were collected systematically to analyze the content of grain size ,clay mineral, radioactivity element (U, Th and K),and cite the content of the authigenic CaCOs from Chen Ye’ doctor thesis.Sediment environment of the Sezhong 6 core is credible.This is the foundation of using natural gamma logging (GR) curves to establish the model of inverse of palaeoclimatic changes. On the different sediment environment in the typical 4 short layers, the correlation between the GR size and the other palaoclimatic indicators is discrepant, but many of them is close. The GR curves fluctuation on millennial or centennial scale is also significant.It is the timescale that occupies an important position in the Quaternary paleoclimatic researches. Because magnetic reversal ages have been modified several times in the past, in order to correlate with other global records, a new orbital tuning scale of Qaidam Basin is needed. The timescale in this paper is up to datings from Yuan Linwang ’ doctor thesis. Using a interpolation at spacing lOOa to gain a centennial scale time sequence.The long period of millennial or centennial scale variations of paleoclimate is a insufficient field. Since the GR fluctuation and the other palaoclimatic indicators has good matching correlation on the millennial or centennial scale, we can use the GR curves to discuss the millennial or centennial scale inverse of palaeoclimate changes, we gain the average 600-800 cycles by analyzing synthetically the GR and other palaoclimatic indicators curves fluctuation in the typical 4 short layers. And the 1467 cycles is validated by the stat of lithology gyration and sedimentary facies. At the same time,there are a series of cycles for the age interval 1.35Ma B P to 2.24 Ma B P by spectrum analysis with the numerical curves of geophysical Gamma logging of the core. Many of these cycles can also be found out in palaoclimatic indicators of the other region, which gives us strong proof.更多还原