羌塘盆地雁石坪地区中侏罗统夏里组沉积旋回与气候演化机制  

Mechanisms of the sedimentary cycles and climatic evolutions in middle Jurassic Xiali Formation in Yanshiping Area,Qiangtang Basin

作　　者：张洒[1] 宋春晖[1] 刘川[1] 潘佳秋[1] 何鹏举[1] 孟庆泉[1] 

机构地区：[1]兰州大学地质科学与矿产资源学院,甘肃省西部矿产资源重点实验室,兰州730000

出　　处：《兰州大学学报（自然科学版）》2015年第3期319-326,共8页Journal of Lanzhou University(Natural Sciences)

基　　金：国家重点基础研究发展计划(973计划)项目(2011CB403000;2013CB956400);中国科学院战略性先导科技专项资助(XDB03020402)

摘　　要：基于藏北羌塘盆地东部雁石坪地区中侏罗统夏里组岩性和沉积物颜色呈现明显的旋回变化特征,通过对其高分辨率岩性、沉积物色度和CaCO_3质量分数分析,并采用Redfit频谱分析,发现岩性、沉积物色度和CaCO_3质量分数波谱分析结果与米兰科维奇旋回周期之间有良好的对应关系,认为由地球轨道效应控制的海平面变化是控制雁石坪地区中侏罗统夏里组沉积旋回发生、发展的主要因素.利用滤波手段分离夏里组CaCO_3质量分数蕴含的主频周期,并结合夏里组岩性、色度、化石和石膏出露层位,把夏里组划分为:早期古气候相对湿润,主要受低振幅波动的岁差周期控制;中期古气候表现为半干旱,由岁差周期功率值猛增至早期的2倍导致;晚期古气候干旱,主要受稳定的岁差周期和强势输入的偏心率周期的协同控制,并认为该时期是盆地可能成盐的最佳气候时段.Based on the apparent cycling characteristics of sediment lithology and coloration of the middle Jurassic Xiali Formation in Yanshiping Area located in the east part of Qiangtang Basin,Northern Tibet,a good correspondence was found between lithology,brightness and spectral analysis of calcium carbonate content and the Milankovitch cycle by analyzing its high-resolution lithology,sediment color and calcium carbonate content through Redfit spectrum analysis.The results showed that the sea level changes controlled by the earth＇s orbit were the main factors effecting the occurring and development of the depositional cycle of the middle Jurassic Xiali Formation in Yanshiping Area.The filter method was used to separate the foremost frequency cycles for calcium carbonate data in the Xiali Formation and,combined with the exposed layers of lithology,lightness,fossils and plaster,the formation was divided into three stages：in the early stage,the paleoclimate was relatively humid and mainly controlled by the low-amplitude precession cycle;in the middle stage,the paleoclimate turned semiarid,which was caused by the power value of the precession cycle jumping to be 2 times of the early stage;in the last stage,the paleoclimate was characterized by drought and mainly controlled by the stable precession cycle and the strongly input eccentricity cycle.In summary,the last stage of Xiali Formation＇s paleochmate changing may be the most suitable climate stage for the formation of potash mine in the Qiangtang Basin.

关 键 词：沉积旋回 地球轨道周期 气候演化 夏里组 羌塘盆地 

分 类 号：P461[天文地球—大气科学及气象学]