贵州威宁麻窝山岩溶盆地剖面沉积物矿物学特征及其古气候指示

发布时间：2018-04-28 08:33

  本文选题：岩溶盆地 + 粘土矿物　； 参考：《贵州大学》2015年硕士论文

【摘要】：贵州威宁麻窝山岩溶盆地受西南印度洋和东南太平洋两种季风的共同影响对气候响应较敏感。盆地内沉积物记录了沉积环境演变信息,是研究气候变化的极佳场所。本文以贵州威宁麻窝山岩溶盆地为研究对象,采用了钻探取样、X射线衍射、粒度分析和钻孔剖面中主量元素和微量元素含量变化分析等手段,分析了剖面沉积物的矿物学特征以及地球化学元素特征。探讨了该地区40ka BP以来的古气候演变,初步得到以下结论。(1)剖面4沉积物矿物主要由粘土矿物(38%~72%)、方解石(0%~39%)、石英(10%~55%)以及长石(0%~3%)等组成,其中粘土矿物含量最多且波动较大,方解石在灰白色湖沼层含量较高,可能与该层出现生物壳体有关。依据粘土矿物总量和方解石含量可将剖面划分为(a-i)9层。(2)粘土矿物组成主要为伊利石/蒙脱石混层矿物(30%~75%)和绿泥石(10%~45%),其次是伊利石(10%)和高岭石(5%~20%),少数样品含蒙脱石。绿泥石与伊/蒙混层矿物相对含量呈此消彼长的关系,且垂向上具有较明显的变化规律,出现多个冷暖—干湿旋回。伊利石结晶度指数和化学指数相较于其他粘土矿物指标更为敏感,在剖面的底部出现较大幅度的波动,存在两个冷暖—干湿小旋回。(3)地球化学元素研究表明,剖面Ti/A1比值、Zr、Rb元素在垂向上均呈规律变化,且剖面间具有较好的一致性,与剖面颜色变化相吻合。Ti/Al高值,对应温暖湿润的气候环境,Ti/A1低值,对应寒冷干燥的气候环境。生物壳体层对应的Ti/Al高值,表明当时的气候比较温暖,降水较丰富,适合生物的生长繁殖。(4)Zr/Rb与粒度具有重要的环境意义,即Zr/Rb值低,湖泊沉积物中细颗粒含量较多,可能指示化学风化作用较强的温度较高,降水丰富的气候环境;Zr/Rb值高,湖盆沉积物中粗粒矿物相对较多,可能指示化学风化作用相对较弱,物理风化占主导地位的温度较低,降水量少的气候环境。(5)通过全样矿物组成、粘土矿物组成以及地球化学元素特征综合分析,可将研究区剖面划分为4个阶段,3个冷暖—干湿大循环,其中第Ⅰ、Ⅱ、Ⅲ阶段分别包含2个冷暖—干湿的小循环。
[Abstract]:The Mawushan karst basin in Weining Guizhou is more sensitive to the climate response under the influence of the two monsoons in the southwest Indian Ocean and the southeast Pacific Ocean. The sediment in the basin records the evolution information of sedimentary environment and is an excellent place to study climate change. In this paper, the Mawushan karst basin in Weining, Guizhou Province, is studied by means of X-ray diffraction, particle size analysis and variation analysis of the main elements and trace elements in the borehole profile. The mineralogical characteristics and geochemical elements of the sediments in the profile are analyzed. The paleoclimate evolution since 40ka BP in this area is discussed, and the following conclusions are obtained preliminarily. 4) the sediment minerals in section 4 are mainly composed of clay minerals 38 and 722, calcite 39, quartz 1010555 and feldspar 0 ~ 3 ~ 3), among which clay minerals are the most abundant and fluctuate. The content of calcite is high in the grayish-white lake, which may be related to the appearance of biological shell in this layer. According to the total amount of clay minerals and the content of calcite, the profile can be divided into 9 layers. 2) the composition of clay minerals is mainly composed of Illite / montmorillonite mixed layer mineral (30 + 7575) and chlorite 1010454545. The next is Illite 104545) and kaolinite 52020. A few samples contain montmorillonite. The relative content of chlorite and the minerals in the Iraq / montmorillonite layer fluctuates in the same direction, and there are obvious changes in vertical direction, and there are many cycles of cold, warm and dry wet and wet. Illite crystallinity index and chemical index are more sensitive than other clay mineral indexes, and there are large fluctuations at the bottom of the profile, and there are two cold, warm, dry and wet cycles. The ratio of Ti/A1 to Rb in profile changes regularly in vertical direction, and there is good consistency between sections, which coincides with the color change of section, the high value of Ti / Al, the low value of Tip / A1 in warm and humid climate environment, and the cold and dry climate environment. The high value of Ti/Al in the shell layer indicates that the climate was warm and the precipitation was abundant. It is of great environmental significance to fit the growth and reproduction of organisms. The ZrR / RB and particle size are of great environmental significance, that is, the Zr/Rb value is low and the fine grain content in lacustrine sediments is more than that in lacustrine sediments. It may indicate that the temperature with strong chemical weathering is higher, the climatic environment with abundant precipitation has a high Zr / R _ b value, the coarse-grained minerals in the sediments of the lake basin are relatively more, and the chemical weathering is relatively weak, and the temperature dominated by physical weathering is relatively low. The climatic environment with less precipitation can be divided into four stages by the comprehensive analysis of the mineral composition, clay mineral composition and geochemical element characteristics of the study area, in which the first, the second, the cold, warm, dry and wet cycles, are divided into four stages. Stage 鈪，

本文编号：1814543