Analysis Of Sequence Stratigraphy And Key Unconformities Of Cambrian-Ordovician In Tarim Basin

Tarim basin is in xinjiang Uygur Autonomous Area of southern China, is the large inland basin which Tianshan Mountains, Kunlun Mountains and Altyn Tagh mountains surrounded. In order to researching the marine carbonate sequence stratigraphic framework and distribution of unconformities in Tarim basin, with the thesis sequence stratigraphy, structural geology, sedimentology theories, combined with drilling, logging, seismic data, the paper research sequence stratigraphy of the Cambrian - Ordovician and key division of the unconformities（T₉⁰, T₇⁴, T₇⁰）in Tarim basin. Develop stratigraphic on the sequence drilling and seismic programs and analyze the various layers Sequence and evolution of spatial distribution, furthermore, in the sequence framework, learn several key features of the unconformities.According to the environmental deposition of Cambrian-Ordovician marine carbonate, through the large scale tectonic movements and the movements of sea level, Cambrian-Ordovician stratum in Tarim basin can be divided into 3 gigasequence, 8 super-sequence. Performance of the Cambrian is extension system in Tarim Basin; in Early Ordovician, the tectonic background in Tarim basin have an important period, thanks to mid-term campaign of Caledonian, turn the extension environment of southern craton in Tarim into the squeezed environment; In the late Ordovician （Caledonian movement）, thanks to further enhancing the areaal compression, large water basin exit.In this study, making key unconformities （T₉⁰, T₇⁴, T₇⁰） interface structure maps, prepare to grasp the developmental characteristics of each unconformity. Through Studying we can show the north area of the Tarim, Bachu area, Tazhong area. These three tectonic uplift area, making burial depth of three unconformities are manifested as shallow; In Manjiaer depression and Awat depression of the northern basin and depression of southwestern of Tarim, burial depth of three unconformities are deep. Each map of unconformities shows the tectonic framework by the interface in the Tarim basin, so we conclude that unconformities may have significant erosion in the three uplift area, may present angular unconformities or superimposed unconformities area; in excessive area of the uplift and adjacent areas, may occur micro perspective unconformities; In other areas, will present parallel consolidation unconformities.Finally, on the basis structure background in the Tarim basin, this construction research on overall background of several key unconformities, unconformities characteristics of drilling revealed under the surface, seismic reflection characteristics of unconformities and lithofacies assemblages qualitative and so on. For the first time, we systematically research on tectonic evolution of two key unconformities （T₇⁴ and T₇⁰） of Cambrian– Ordovician in Tarim basin. T₇⁴ characteristics of unconformities were integrated in Caledonian movement mid- period, the Caledonian late period, Hercynian movement early period, late Hercynian movement period, the Indo-Chinese Movement period. T₇⁰ characteristics of unconformities were integrated in the late Caledonian period, Hercynian early period, late Hercynian period.