Regulation Of Sediments Distribution And Sedimentation-sequence Filling Characteristics During Late Paleozoic In Ordos Basin

In this thesis, drawing on the basis of previous research, guiding by the academic ideology of "structural control basin, basin control sediment, sediment control combination", emphasizing restriction of global tectonic to the tectonic evolution of Ordos basin,using those theories of sedimentology, paleontology, high-resolution sequence stratigraphy, sedimentary geochemistry and geophysics, based on outcrops and logging and seismic data, studied the regularity of sedimentation-sequence filling characteristics and sediments distribution in the late Paleozoic Ordos basin. The main content and achievements are as follows:First, starting from the global pattern of plate tectonics, focusing on the Great North China regional context, the guiding ideology are the superimposed tectonic dynamic and compound of the Paleo-Asian domain, Tethyan tectonic domain and Sea Pacific tectonic domain ,which control and influence the tectonic evolution of the Ordos Basin at different stages of the formation and development. Based on the above analysis, the Ordos Basin Paleozoic is mainly Controlled system of the Paleo-Asian tectonic geodynamic background dynamics.Second, by studying lithostratigraphy, biostratigraphy and chronostratigraphy of the upper Paleozoic in Ordos basin, the outcrops and drilling is carried out a systematic stratigraphic division and contrast. The author takes the stratigraphic and sedimentary process-response dynamic principles as a theoretical basis, and applies the theory and technology of the high-resolution sequence stratigraphy on base-level cycle. After research on the types of sequence boundary and classification standard, identifing six kinds of different causes of sequence boundaries and three basic types, seven subtypes different grade of base-level cycle sequence filling patterns. Finally, sequence stratigraphy division plan of lower Paleozoic in Ordos basin is set, the upper Paleozoic can be divided into three super long-term, twenty long-term, fouty-seven medium-term and several short-term cyclic sequences, and sequence stratigraphy framework is established. Third, using sedimentary geochemical proxies, distribution of marine stratum, fossils, sedimentary tectonics, petrology and sedimentary diagenesis, establishing the geochemical proxies section of east-west and north-south in Ordos basin, and analying the test results of different layers in different regions. On the base of the above analysis, the depositional environment during Shanxi period of early Permian was deeply analyzed in this paper. The author think that the conversions of marine-continental facies during the upper Paleozoic in Ordos basinis is later Shanxi period.Forth, referring to the predecessors's research, choosing isopach map of different periods of lithostratigraphic units, approximately characterizing the different stages of the ancient structural features during Paleozoic in Ordos basin, furtherly strengthening the understanding of formation and evolution of central paleouplift. The results show that the real central paleouplift is formed during late Cambrian, and reflects obviously during the Majiagou period of Ordovician. The main influences of the late Paleozoic is the late Carboniferous-early Permian, and die away from the diversification background of east-western extension and north-southern extrusion in the Permian period of Lower Shihezi. Summary, the formation and evolution of central paleouplift of the Paleozoic is divided into six major stages in Ordos basin, and discussing the deposition distribution of it.Fifth, On the basis of the changes of marine-continental facies during late Paleozoic in Ordos basinis, and analying the adjustment and disappearance of central paleouplift in the Paleozoic, the structure paleogeographic of North China basin are drew systematic. The sedimentary evolution of Ordos basin is divided into three major stages, including restricted epeiric sea in the late Carboniferous-early early Permian (Benxi-Taiyuan period), remaining epicontinenta sea and offshore basin in the The late early Permian (Shanxi period), and continental basin in the middle-late Permian (lower Shihezi-Shiqianfeng period). Final the author has discussed the sedimentary evolution and structure paleogeographic of different kinds of stages.Sixth, basing on outcrops and logging and seismic data, studying the development features of typical sedimentary environment. On the one hand, focusing on the mixed siliciclastic-carbonate sediments during late Carboniferous-early early Permian (Benxi-Taiyuan period). And analyzing the genetic mechanism and sedimentary characteristics of such kinds of sediments, identifing three main types of mixed sedimentary environment, which include the types of epeiric sea, barrier coast and shallow water delta. Fially, the mixed sediments model in Ordos basin is set. On the other hand, basing on analysis of genetic mechanism of shallow water deltas during late Paleozoic in Ordos basinis, analyzing sedimentary characteristics of them and identifing four main types of them, which include the types of gentle marine slope-type shallow meandering river delta (Taiyuan period), gentle river-tide controlled slope-type shallow braided river delta (Shan 2 period), transition phase slope-type shallow meandering river delta (Shan 1 period) and lacustrine slope-type shallow braided river delta(He 8 period). And studying the regulation and difference of such deltas, Fially, the sediments model of shallow deltas in Ordos basin is set.Seventh, basing on establishment of the sequence stratigraphy framework, determination of the conversions of marine-continental facies,analysis of the adjustment and disappearance of central paleouplift and segmentation of the sedimentary evolution of Ordos basin, discussing the regulation of sediments distribution and the process of sedimentation-sequence filling during late Paleozoic in Ordos Basin. It is based on super long term base-level cycle as a period, the sequence paleogeographic and sand isopach map during of lower Paleozoic in Ordos Basin were drew, which revealed the sediments distribution, the sedimentary evolution and sand distribution in different periods of late Paleozoic in Ordos Basin. On the base of the above analysis and sedimentation-sequence filling in different super long term base-level cycles, discussing the regulation and difference of sedimentary evolution of Ordos basin during late Paleozoic in Ordos Basin.