新疆柴窝堡盆地南缘晚新生代陆源沉积物岩石磁学特征及其古环境意义

发布时间：2018-10-30 13:02

【摘要】：亚洲内陆晚新生代干旱化历史及其驱动机制是非常重要的科学问题。选择天山北麓柴窝堡盆地南缘乌鲁木齐河剖面为研究对象,基于磁性地层年代学研究建立的时间标尺,分析了该剖面碎屑沉积物岩石磁学特征及其控制因素,进一步探讨了柴窝堡盆地晚新生代古气候特征。磁性地层年代学研究约束乌鲁木齐河剖面底界年龄为~6.8 Ma,顶界年龄为~3.3 Ma。详细的岩石磁学测量及漫反射光谱分析结果表明,乌鲁木齐河剖面沉积物中磁性矿物主要包括磁铁矿、赤铁矿等,磁学参数X_(lf)、X_(ARM)、SIRM、S_(-100m T)、S_(-300m T)、X_(ARM)/SIRM等在~6.3 Ma、~5.2 Ma存在明显变化,揭示磁性矿物粒度、含量等存在相应变化,如在"6.3 Ma前后,磁性矿物颗粒逐渐变粗、含量降低;在"5.2 Ma前后,磁性矿物颗粒逐渐变细后趋于稳定、含量逐渐增多。基于稀土元素分析、沉积粒度与磁学参数相关性分析,认为沉积物源与沉积物粒度不是导致乌鲁木齐河剖面磁学性质变化的主要因素,自~6.8Ma以来逐步干旱化的气候条件可能是导致该剖面磁学特征变化的重要原因。基于漫反射光谱分析得到的红度与亮度数据结果也揭示了同样的古气候特征。
[Abstract]:The late Cenozoic drought history and its driving mechanism in inland Asia are very important scientific issues. The Urumqi River section in the southern margin of Chaiwupu basin in the northern part of Tianshan Mountain is selected as the research object. Based on the time scale established by the chronological study of magnetic stratigraphy, the magnetic characteristics of clastic sediments and its controlling factors are analyzed. The paleoclimate characteristics of the late Cenozoic in Chaiwupu basin are further discussed. The geochronological study of magnetic stratigraphy constrains the bottom boundary age of Urumqi River section to be ~ 6.8 Ma, top boundary age ~ 3.3 Ma.. Detailed rock magnetic measurements and diffuse reflectance spectroscopy analysis show that the magnetic minerals in the sediments of the Urumqi River profile mainly include magnetite, hematite, etc., and the magnetic parameter X _ (lf), X _ (ARM), SIRM,S_ (-100m T),) S300m T), X _ (ARM) / SIRM has obvious changes in ~ 6.3 Ma,~5.2 Ma, which reveals the corresponding changes in the particle size and content of magnetic minerals. For example, before and after "6.3 Ma, the magnetic mineral particles gradually become coarser." Content decreased; Before and after 5. 2 Ma, the magnetic mineral particles became more and more fine, and the content of magnetic minerals gradually increased. Based on the analysis of rare earth elements and the correlation between sediment granularity and magnetic parameters, it is concluded that sediment source and sediment granularity are not the main factors leading to the change of magnetic properties in the Urumqi River profile. The climatic conditions of gradual drought since ~ 6.8Ma may be an important reason for the change of magnetic characteristics of the profile. The same paleoclimate features are also revealed from the redness and brightness data based on diffuse reflectance spectroscopy.
【作者单位】：华东师范大学地理科学学院;
【基金】：国家自然科学基金项目(41371031,J1310028)~~
【分类号】：P318.44;P534.6

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