湘西北花垣县下寒武统清虚洞组浊积岩沉积特征及其地质意义

Sedimentary characteristics and geological significance of turbidites in the Lower Cambrian Qingxudong Formation at Huayuan county,northwestern Hunan

湘西北花垣县及邻区,在下寒武统清虚洞组下部发育一套地质特征典型、沉积序列明显的浊积岩。其底面侵蚀构造清楚,覆盖于底面上的各层段厚度变化较大,在各层段内由下往上碎屑粒度依次变细,并相继出现有变形纹层、平行纹层和波痕纹层理等沉积构造,是典型的浅海浊积岩。据各层段的发育情况可总结为5种剖面结构。因冰川消融而使海平面上升,故清水洞组浊积期海水深度增大。浊流活动受北东东向保靖—花垣断裂控制,其活动与新元古代发生并延续到早古生代的罗迪尼亚超大陆裂解事件有关。

This paper described main geological characteristics and typical sedimentary successions of the Lower Cambrian Qingxudong Formation at Huayuan county in northwestern Hunan province. Its erosion structure in the base was clarity,the thickness varied obviously from section to section,and grain size of clastic sediments became finer in an upword order,accompanied with occurring of deformed lamination, parallel lamination and corrugated lamination. All of these sedimentary structures indicated the turbidites deposited in an offshore environment. Based on development of Bouma sequence, five profile textures of the turbidites were concluded. The glacial ablation resulted in sea level rising, so the seawater became deeper during depositional period of the Qingxudong Formation. The turbidity current, widely distributed in northwesten Hunan and northeastern Guizhou areas, was controlled by the NEE-striking faults, and in Huayuan the current controlled by the Baojing-Huayuan fracture. The activity of the NEE-striking faults in Early Cambrian might be related to splitting of the Rodinia supercontinent, which occurred in Neoproterozoic and continued to Early Paleozoic.