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| 黄土古气候变化趋势与青藏高原隆升关系初探 | |
| 引用本文： | 刘秀铭,毛学刚,丁仲礼,吕镔,郭雪莲,陈渠,陈家胜,贾佳,杨善林,Hesse Paul,陈发虎.黄土古气候变化趋势与青藏高原隆升关系初探[J].第四纪研究,2009,29(5):988-999. |
| 作者姓名： | 刘秀铭 毛学刚 丁仲礼 吕镔 郭雪莲 陈渠 陈家胜 贾佳 杨善林 Hesse Paul 陈发虎 |
| 作者单位： | 1. 兰州大学资源环境学院西部环境教育部重点实验室,兰州,730000;Department of Physical Geography,Macquarie University,NSW 2109 Australia 2. 兰州大学资源环境学院西部环境教育部重点实验室,兰州,730000 3. 中国科学院地质与地球物理研究所新生代地质与环境重点实验室,北京,100029 4. Department of Physical Geography,Macquarie University,NSW 2109 Australia |
| 基金项目： | 国家自然科学基金项目，教育部博士点基金项目，甘肃省自然科学基金项目 |
| 摘 要： | 粒度和磁化率是两个研究黄土古气候最常用的古环境变化指示参数，它们随着黄土古土壤地层变化而出现峰和谷的对应已经被证明是反映了天文轨道要素的周期变化。文章试图忽略这些受控于轨道要素的气候周期变化，而主要侧重考察黄土地层这两个参数的平均值(或背景值)所反映的长期变化趋势。对兰州九州台黄土进行了系统采样和测量，发现兰州九州台黄土剖面粒度和磁化率曲线显示出两个明显的趋势，粒度从剖面底部向上有明显逐渐变粗趋势，指示着冬季风增强，与此同时，磁化率自下而上却逐渐增大，指示着夏季风增强的趋势。与黄土高原其他黄土剖面磁化率和粒度曲线对比发现，这是两个普遍存在的趋势。地理位置靠近青藏高原的剖面，这两个增大的趋势更明显。冬、夏季风同时逐渐增强是海陆热力差异增大所引起，反映了青藏高原第四纪时期的逐渐不断的隆升过程。因此，根据粒度和磁化率曲线变化趋势线的变化特点可以帮助分析和反推第四纪以来青藏高原隆升的过程。兰州九州台以及黄土高原各剖面粒度和磁化率曲线的线性变化趋势则可能指示着第四纪以来青藏高原是逐渐均匀缓慢的变化过程。我们对22Ma以来风积地层记录的变化趋势也做了分析。前人过去普遍认识的第四纪以来跳跃式或间歇式剧烈隆升在我们的数据中没有得到反映。黄土高原西部西宁、兰州、靖远等剖面磁化率显著的增长趋势可能与青藏高原隆升到一定高度后高原季风加强所致。 |
| 关 键 词： | 兰州九州台 第四纪黄土 黄土高原冬－夏季风变化趋势 青藏高原隆升 趋势分析 |
STUDY ON THE RELATION BETWEEN LOESS PALEOCLIMATE TREND AND UPLIFT OF TIBETAN PLATEAU |
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| Liu Xiuming,Mao Xuegang,Ding Zhongli,Lu Bin,Guo Xuelian,Chen Qu,Chen Jiasheng,Jia Jia,Yang Shanlin,Hesse Paul,Chen Fahu.STUDY ON THE RELATION BETWEEN LOESS PALEOCLIMATE TREND AND UPLIFT OF TIBETAN PLATEAU[J].Quaternary Sciences,2009,29(5):988-999. | |
| Authors: | Liu Xiuming Mao Xuegang Ding Zhongli Lu Bin Guo Xuelian Chen Qu Chen Jiasheng Jia Jia Yang Shanlin Hesse Paul Chen Fahu |
| Institution: | Key Laboratory of Western China's Environmental Systems|Ministry of Education|College of Earth and Environmental Science|Lanzhou University|Lanzhou 730000|Department of Physical Geography|Macquarie University|Sydney NSW 2109, Australia|Key Laboratory of Cenozoic Geology and Environment|Institute of Geology and Geophysics|Chinese Academy of Sciences|Beijing 100029 |
| Abstract: | Grainsize and magnetic susceptibility are two basic and most useful parameters for studying paleoenvironmental change in loess and paleosol sequences. Their variation of peaks and valleys with loess and soil layers has been confirmed to be controlled by Milankovich cycles. These climatic records，therefore，are the function of time. Based on cycle theory，its long term trend should be a straight line，superposition or parallel to time axes. However，the curves of Jiuzhoutai loess section in Lanzhou show two obvious trends(Fig.2)．Grainsize gradually becomes coarser from the bottom to the top，which implies winter monsoon becoming stronger. At the same time，the value of magnetic susceptibility gradually increases，which implies summer monsoon becoming stronger. These two trends are also ubiquitous in other sections of the Loess Plateau. We attribute the trend of this noncycle factor to the uplift of Tibetan Plateau，This trend show an angle(or slope)to the time axes. The size of angle or slope is therefore related to the intensity of uplift. By examing long term tendency of grain size and susceptibility for the last 22Ma's aeolian deposit(data for 22.0～2.6Ma from ref.35,36,46,67,68])，our data show two 3 pieces of straight trend lines(3 uplift stages)separated by two transition points. Two turning points were occurred around 8.0Ma and 2.6Ma respectively，responding to two major relatively sudden and strong uplifts of Plateau. During period of 22～8Ma46,67]，this tendency is a straight line paralleling to the time axes. This behavior indicates constant elevation of the Plateau during the time. In between 8.0～2.6Ma35,36,68]，there was a small angle between the trend straight line and time axes，suggesting a stable rate of uplifting Tibetan Plateau. From 2.6Ma to the present day，angle between the trend straight line and time axes is slightly bigger(Fig.2～4)，recommending the Plateau uplift at even higher rate then before. The linear trends of grainsize and magnetic susceptibility from loess deposits over the Loess Plateau suggest Tibetan Plateau gradual，uniform and slow uplift，instead of former common idea: saltatory or intermittent but violent uplift in Quaternary period. If 2.6 million years was taken as the Quaternary lower boundary,3000 meters in Xixiabangma region of the Tibetan Plateau has been uplifted since Late Tertiary according to plant fossils study，annual average rate of 1.15mm during Quaternary period can be calculated. |
| Keywords: | Jiuzhoutai section in Lanzhou Quaternary loess Loess Plateau winter summer monsoon trends Tibetan Plateau uplift trend analysis |
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