| This paper centers on two questions,namely sedimentary evolution and sequence Stratigraphy in middle Qiangtang Basin.And Middle-Upper Jurassic is seleceted as object of study. Litho stratigraphy, biostratigraphy, chronostratigraphy and sedimentary geological is Systematically studied in the one part of the thesis, the stratigraphic framework and petrology, sedimentary facies, lithofacies and paleogeography, and sedimentary evolution of the study area is deeply analyzed and explored; in the other part, The Author studies third-order sequence stratigraphy characteristics of the middle-upper Jurassic in the area, based on the outcrops and route geological, and explores the influencing factors on formation of the sequence stratigraphy. The two parts are closely related, study sequence stratigraphy must be based on well stratigraphy and sediment logy research, but the available information is far from being able to meet this need. If the first part of the paper is as a basis and regional geological study, then the latter part of the paper may be the study of cutting-edge geological problems, which together constitute this paper. To sum up, this thesis got the following conclusions:1.An stratigraphic framework on Jurassic is established. The Jurassic in Study area bottom-up divided into five lithostratigraphic units from the Quemocuo Formation, the Buqu Formation,the xiali Formation, the Suowa Formation and to the Xueshan Formation. Each integrats contact between the Formations, and they were coveraged angular unconformity by the Cretaceous, Paleogene, Neogene or Quaternary. On the basis of detailed study of Lithostratigraphic, Biostratigraphic and Chronostratigraphic, the basic sequence, paleontology combination of stratigraphic classification and comparative was analysised.2.Sedimentary characteristics of the middle-upper Jurassic in the study area that Quemocuo Formation is a set of quartz sandstone, siltstone and mudstone, limestone sedimentary assemblages. The Buqu Formation is a micrite, micrite,(inclusive) bioclastic limestone (inclusive) particles of limestone and light grain limestone mudstone combination. a set of sandstone and few mudstone combination and Micritic bioclastic limestone composes of the Xili Formation. And the Suowa Formation composed of a set of sandstone and mudstone and bioclastic limestone, micritic limestone. a set of sandstone and few mudstone for Xueshan Formation. Simultaneously the color, authigenic minerals, sedimentary structures, sedimentary structures about those Formations was studied, and they variation disciplines was investigated.3. Based on the analysis of sedimentary facies in Tumen and the Shuanghu two single profile deposition, in the study area, sedimentary facies types and distribution on the middle-upper Jurassic were analyzed. The Author believes that the Quemocuo Formation was carbonate platform facies-based Delta environment,whereas the Buqu Formation was a carbonate platform facies, and the Formation Xiali shore deposits,the Suowa Formation carbonate platform facies also, but the xuehsna Formation was Delta, a foreshore and shallow lake environment.4. On the basis of the petrology and sedimentary facies in the study area, the rock paleogeography and sedimentary evolutionone on the middle-upper Jurassi in the area was systematically discussed and further, the Jurassic sedimentary historyin the area was explored.5. The initial establishment of the third-order sequence of the study area. Under the guidance of theory of outcrop sequence stratigraphy, by analyzing the response of the Middle-Upper Jurassic sedimentary characteristics to sequence stratigraphy, the second order sequence stratigraphy of the Middle-Upper Jurassic was divided into nine third-order sequence, and system tract was distinguished in the study area. After a Regional comparison of the sequence, and that tectonism and global sea-level change as the primary factors for controlling the third order sequence in the study area, secondly by climate and sediment supply.Carrying out sequence stratigraphy on the Middle-Upper Jurassic in the area has two potential scientific significance:Firstly,Jurassic global sea level has been extensive research and fruitful, to conduct a detailed study on the study area deposited in the Tethys north shore one when Jurassic, to lay the foundation for the geological characteristics of the eastern section of the Tethys and the global over the same period compared; secondly,the division and correlation of the third sequence, is third order cycles of division and correlation,with the same global sea level changes could be divided into nine periods, and this might lay the foundation for the division and correlation of the higher-level cycles. |
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