Sedimentary characteristics and controlling factors of deep-water gravity flow deposits of the Oligocene in Tanzania Basin
Guo Xiao1,2, Li Hua1,2, Liang Jian-She3, Qiu Chun-Guang3, Xie Dong-Ning3, Feng Xin3, Rao Su3, He You-Bin1,2
1 School of Geosciences,Yangtze University,Wuhan 430100,China; 2 Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education,Yangtze University,Wuhan 430100,China; 3 CNOOC Research Institute Co.,Ltd.,Beijing 100028,China
Abstract：In recent years, several large-scale gas reservoirs have been discovered in Tanzania Basin of the East Africa. However, the study of sedimentary characteristics, formation mechanism and main controlling factors are relatively weak. Based on drilling, logging and 2D seismic data, with the comprehensive analysis of the sedimentary characteristics, it is found that deep-water gravity-flow deposits were developed in Oligocene of Tanzania Basin. The deep-water deposits could be divided into 3 types: channels, levees and lobes, among which channels and lobes are dominated. Moreover, deep-water channels could be further divided into the complex channel, the lateral-migrational channel, the vertical-aggradational channel and the isolated channel, according to the occurrence location, external morphology, internal architecture and sedimentary style. There were variations in sedimentary characteristics of Oligocene gravity-flow deposits from south to north of the Tanzania Basin. In the south of the basin, the small-scale isolated channels and lobe deposits were developed, which have a SW-NE orientation. In the middle of the basin,complex channels, vertical-aggradational channels, lateral-migrational channels and lobe deposits were mainly developed, with a overall orientation of NW-SE direction. In the north of the basin, lateral-migrational channels, levees and lobe deposits were dominated, which have similar orientations to those of the middle part. Taking the variations among the south, the middle and the north parts of Tanzania Basin and the coupling relationships of Source-to-Sink into consideration, the elements of Source-to-Sink system is comparatively analyzed. Research suggests that the development and distribution of deep-water gravity-flow deposits in the study area are mainly affected by tectonic movements (the tectonic uplift, mid-ocean ridge spreading, and fault activity), source systems and the shelf-slope topography.
Guo Xiao,Li Hua,Liang Jian-She et al. Sedimentary characteristics and controlling factors of deep-water gravity flow deposits of the Oligocene in Tanzania Basin[J]. JOPC, 2019, 21(6): 971-982.
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