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| Grain size characteristics and sedimentary environment analysis of flysch in Langjiexue Group of Tibet |
| ZHANG Liguo, WANG Jingui, WANG Shuo, YANG Xinpeng, CHENG Zhou, HOU Dehua, CHEN Yuanyuan |
| Regional Geological Survey Institute of Hebei Province, Langfang 065000, China |
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Abstract Langjiexue Group is an important part of the stratigraphic sequence of the ocean plate in Yalu Tsangpo River junction zone, and its formation environment is of great significance to the Neo-Tethys tectonic movement. The authors have systematically summarized the characteristics of rock assemblage and tectonic deformation in this paper. And four basic sequences have been established by recognizing Bauma sequence. According to the analysis of material composition, structure and sequence, it is considered that the submarine fan facies model is developed in this area, which belongs to turbidite fan especially inner-outer fan subfacies environment as a whole. A small part of the main channel of subfacies of the sand conglomerate sedimentation was developed, with the transition of Bauma sequence from A, C member to B, C, D member and C, D, E member, reflecting the characteristics of the transition from high to low fluidity. On the basis of the grain analysis of the maturity, sorting, transportation and sedimentary forms of the material composition of Langjiexue Group, the authors consider that the grain size curves of Langjiexue Group are similar to those of Hudson turbidite fan and modern deep-sea Aristoa fan. And it belongs to the turbidite depositional type in gravity flow deposits, indicating that Langjiexue Group was formed in continental slope environment.
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Received: 01 February 2019
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2020, Vol. 7 
