论文部分内容阅读
对黄土高原的灵台和泾川黄土 -红粘土序列进行了磁性地层学和沉积学研究.古地磁研究表明,泾川剖面的底界年龄为 8.0Ma,这比灵台剖面的底界年龄老 1.0Ma.通过空间上红粘土剖面的地层对比,发现灵台红粘土序列相对较为完整和连续.该剖面可以作为中国北方晚第三纪红粘土的标准剖面.野外观察和粒度分析均表明灵台和泾川红粘土沉积为风成沉积.通过对南北向黄土大断面粒度参数的系统分析,初步建立了 粉尘沉积的粒度参数———沉积区距源区最小距离"的半定量模型.根据这些模型推测,红粘土的主要源区可能在现代的巴丹吉林沙漠及其以西地区.灵台剖面的游离铁/全铁值变化表明,晚中新世以来东亚夏季风经历了非线性的演化历史.约 4.1～ 4.8Ma间为黄土高原地区 7.0Ma以来东亚夏季风最为强盛的时期.该气候事件的出现可能同全球温度背景较高及全球冰量较小有着动力学上的联系.
Magnetostratigraphy and sedimentology research on the Lingtai and Jingchuan loess-red clay series on the Loess Plateau.The paleomagnetic study shows that the bottom boundary age of the Jingchuan section is 8.0Ma, which is 1.0Ma lower than the bottom boundary of the Lingtai section Through the stratigraphic comparison of the red clay profiles in the space, it is found that the sequence of the Lingtai red clay is relatively complete and continuous, which can be used as the standard section of the Late Tertiary Red Clay in northern China.The field observation and the particle size analysis both show that Lingtai and Jingchuanhong Clay sediments are aeolian deposits.Based on the systematic analysis of the large-scale grain-size parameters of the loess in the north and south, a semi-quantitative model for the particle size parameters of dust deposition, ie, the minimum distance from the source region in the sedimentary region, is established. According to these models, The main source area of red clay may be in the modern Badain Jaran Desert and the west of it.The variation of free iron / total iron value of Lingtai section shows that the East Asian summer monsoon experienced a non-linear evolutionary history since the Late Miocene about 4.1 ~ The 4.8Ma period is the most powerful period of the East Asian summer monsoon since the 7.0 Ma in the Loess Plateau.The occurrence of this climate event may be related to the higher global temperature background and the global ice volume Little has a kinetic connection.