A STUDY ON SEDIMENTARY SUCCESSIONS AND THEIR INDICATIONS FOR ENVIRONMENT OF DALONG FORMATION AT MATAN, HESHAN, GUANGXI
Lan Chaoli1, Li Jiliang1, Zhang Xiaohui1, Yu Liangjun1, Xia Wenchen2, Fan Jingliang3, Zhang Junfeng4
1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029; 2. China University of Geosciences, Wuhan 430074; 3. Department of Earth Science, University of Petroleum, Beijing 102249; 4. Exploration and Production Corporation, China Petroleum Ltd. Co., Beijing 100724
The Dalong formation at Matan, Heshan County, Guangxi, is mainly composed of pyroclastic rocks and siliceous rocks. A microscopic analysis reveals that the pyroclastic rocks can be subdivided into three subtypes, namely, tuffs, sedimentary tuffs and tuffaceous sedimentary rocks, and further into eight microfacies. The siliceous rocks can be subdivided into two subtypes, namely, biogenic siliceous rocks, bio-and volcano-genic siliceous rocks, and further into five microfacies. These microfacies make of twelve types of main lithofacies, which can be, vertically, grouped into six sedimentary successions. These successions indicate there are two types of turbidity current. One is low-density turbidity current which is evolved from high density turbidity current generated by pyroclastic debris current induced by subaqueous volcanic eruption; another is induced by slumps and brings early sediments of tuffaceous grains and siliceous biogenic grains for the studied area. Our research for sedimentary successions and geomorphology of Matan at this stage demonstrates that there do not exist submarine fans. On the contrary, a low-density tuffaceous tubidity current may be more readily accepted, which results in extensively and relatively thin-bedded deposits.
Lan Chaoli,Li Jiliang,Zhang Xiaohui et al. A STUDY ON SEDIMENTARY SUCCESSIONS AND THEIR INDICATIONS FOR ENVIRONMENT OF DALONG FORMATION AT MATAN, HESHAN, GUANGXI[J]. Chinese Journal of Geology, 2001, (1): 43-50.