三峡库区川东-鄂西早-中侏罗世地层的精细对比及沉积环境变化

Correlation of the Early-Middle Jurassic strata in the Three Gorges area and discussion of sedimentary environments

根据地层层序、岩性特征和化石组合带所提供的时代信息,三峡东部早-中侏罗世香溪组、泄滩组下段、上段和陈家湾组应分别与三峡西部自流井组珍珠冲段下-中部、珍珠冲段上部-东岳庙段、马鞍山段-大安寨段和新田沟组精细对比。指出三峡库区早-中侏罗世古地理大致呈现由河道、河漫湖泊沼泽相含煤沉积→典型的湖泊相沉积→河流与湖泊相周期性交替沉积的变化规律。在分析岩组特征和植物所指示的气候基础上,推测早-中侏罗世气候的变化趋势是,由炎热潮湿逐渐变为炎热干旱。

According to the stratigraphic sequences, lithological characteristicsand fossil assemblages, the Early-Middle Jurassic Xianxi Formation, the Lower Member of Xietan Formation, the Upper Member of Xietan Formation and the Chenjiawan Formation in the eastern Yangtze Gorges may be correlated respectively with the Lower-middle parts of Zhenzhuchong Member, the upper part of Zhenzhuchong Member-Dongyuemiao Member, the Ma'anshan-Da'anzhai Member of the Ziliujing Formation and the Xintiangou Formation in the western Yangtze Gorges. It has been pointed out that the Early-Middle Jurassic palaeogeographies showed regular changes from coal-bearing deposit of river channel, fluviatile flood plain lake or marsh facies to typical lake facies deposit to alternate deposit of river and lake facies. Analyzing of lithological characteristic and fossil plants indicates that the Early-Middle Jurrassic palaeoclimate changed gradually from the hot humid to arid.