Abstract:

In the Upper Yangtze Platform,a large amount basalt show linear and planform eruption,contemporaneous faults are well developed,and mutual restrictive relationship exists between epidermic fold and fracture trace systems and fault blocks.Study of sedimentary records in combination with these observations shows the platform during its formation experienced three drastic up-and down-turns,countless strong tearing and two large-scale tearing,causing strong subsidence in some areas and the formation of several intraplatform troughs.In the eastern part of the platform,nine fault blocks are recognized from north to south,namely Dabashang frontal fault block,Huayinshan,eastern platform margin,Yongchuan-Yibin,Chishui-Gudao-Yanjin,Bijie-Zhenxiong,Qianxi-Dafang,Zhijing-Nayong,and Puding-Puan fault blocks.The distribution of these fault blocks is mapped for the first time.The unbalanced subsidence and uplifting among fault blocks caused the tilting of these fault blocks with one side elevated,which controlled the growth of biogenic reefs and the development of dolostones,finally leading to the formation of reef-controlled reservoirs.During the Late Permian,the Dabashang frontal fault block upwarped at its west end,downwarped at its east end,uplifted in the south side,and tilted to the north;while the Huayinshang and Dongbutaiyuan fault blocks upwarped at its north end,downwarped at its south end,elevated in the east side,and tilted to the west.It is therefore suggested that exploration of reef-controlled reservoirs should follow the following principles:paying attention to structural control of fault block on reservoirs;drilling order being from the upwarped end to the downwarped end and from the elevated side to the tiled side;and performing sedimentary facies analysis before drilling when neither growth of biogenic reef nor tilting of fault block is known.

Key words: tectonics, fault block, platformal trough facies, tectonic system, sedimentary record, bio-reef mode, late Permian, Upper Yangtze Platform