Sequence Stratigraphic Framework And Basin Filling Evolution From Upper Jurassic To Neogene In Yangtze

Based on the theories and methods of sedimentology, sequence stratigraphy and geochemistry, the stratigraphic division and correlation,depositional system, sequence stratigraphic framework, palaeocurrent and provenance types were studied systematically from Upper Jurassic through Neocene in the mid-Yangtze area, China. Then, the palaeogeographic evolution character was analysised and a series of palaeogeographic maps were made. At last, the basin filling sequence and evolution model have been established in different temporal and spatial, and tectonic movements and its control on basin filling patterns have been discussed about the mid-Yangtze area. The main conclusions are as follows:?1? In regard to stratigraphic division and correlation, the researched area was divided into three blocks including Youyang, Jianghan and Edong. The strata of Upper Jurassic mainly distributes in Zigui basin of Youyang; the Lower Cretaceous is main in Yichang, Jingshan and Yingcheng of Jianghan and scatters in Huangshi of Edong; the Upper Cretaceous- Neocene is mainly in Jianghan.?2? Based on outcrop sections, combined with drilling, logging and seismic profiles, five sedimentary facies were identified which included alluvial fan, braided river, meandering river, delta and lacustrine facies, and four depositional modes were constructed which included four combinations alluvial fan-braided river-lacus, alluvial fan-river-delta-lacus, subsea apron-lacus and river-delta-lacus.?3? After the outcrop-based sedimentologic, well logging and seismic stratigraphic analyses of the studied area, 31 sequence boundaries were identified. The sequence boundaries divide the Upper Jurassic through Neogene into 30 sequences in Zigui basin and Jianghan basin. Considering the tectonic movement, the 30 sequences are divided into 9 supersequences and 5 tectono-sequences.?4? A comprehensive statistical analysis were made for palaeocurrent based on outcrop section in margin of the mid-Yangtze,and combined with composition of sandstone, rare earth elements and trace elements analysis and carbon and oxygen isotope analysis, the nature of provenance and tectonic setting have been discussed.In the end, we conclude that the depositional setting of the Upper Jurassic in Zigui basin is foreland basin because of impaction of Qinling-Dabieshan orogenic belt and Jiangnan fold-thrust belt and restriction of Huangling anticline. The alluvial fan and fluvial depositional systems are identified in Nanjinguan due to the fast uplift of Huangling anticline in lower Cretaceous. The depositional setting of the upper Cretaceous in the northern Yangtze block is fault basin and in the southern Yangtze block is the analogous foreland Basin. The depositional filled pattern in the Paleocene is dominated by two groups fault systems. The first strike ?K₂y-Ex? is NE or NEE and the second one (E_j-E_jh) is nearly EW, and two sets of oil-generating strata covering strata have been deposited. The Neogene only exist in Jianghan basin Because of the uplift of all Yangtze block in Himalayan tectonic period. Overall, the mid-Yangtze experienced three major stages of deformation which include intracontinental compression deformation from Late Jurassic to Early Crataceous, fault depression from Late Crataceous to Paleogene and integral deprsssion in Neogene.