湘西北地区五强溪组沉积环境分析与区域对比

Sedimentary environment analysis and regional comparison of Wuqiangxi Formation in Northwestern Hunan province

本文通过野外与室内详细观察,对湘西北古丈五强溪组的岩性特点、沉积相和古地理环境进行了综合分析。结果表明,通塔湾末期湘西北经历短暂快速海退后,五强溪初期海平面缓慢回升,期间形成的积间断面,由下而上发育河流、三角洲平原、三角洲前缘3种沉积相,沉积时限在800 Ma左右,向北西扬子古大陆一侧的盆缘地带可能逐渐变新,形成依次超覆的"楔状地层"特征。以此为基础,对比邻区张家湾组沉积相特点,结合同位素年龄资料,认为横向上张家湾组与五强溪组是在同一个沉积体系中的大致同期沉积物,相序配置反映古水流主体方向自NW向SE,水体自NW向SE逐步加深。

In this paper, lithologic characteristics, sedimentary facies and paleoenvironment of Wuqiangxi Formation, Guzhang area, Northwestern Hunan province are researched through detailed field and laboratory observations. The results show that, the fast transient regression was happened in later Tongtawan stage, and then the sea level rise slowly begin at earlier Wuqiangxi stage, and formed three plot discontinuities of fluvial facies, fiver plain facies and delta front facies from bottom to the top at about 800 Ma. And to the northwestern side of Yangtze ancient continent the age of strata become newer which in turn overlies and got into the ＂wedge formation＂. Stratigraphic correlation shows that Zhangjiawan Formation of adjacent area and Wuqiangxi Formation are deposited in the same sedimentary system inroughly the same period, and sediments reflect that paleocurrent main direction from northwest to southeast, water gradually deepened from northwest to southeast.