Analysis Of Sedimentary Facies And Stratigraphic Correlation Of Permo-carboniferous In Tarim Platform Area

In this dissertation, the Permo-carboniferous strata of the Tarim Basin is treated as the research object. Based on the combination of previous studies, core, log, logging lithology, seismic and outcrop data, utilizing rock stratigraphy, sequence stratigraphy, sedimentology and seismic data interpretation principles and methods, the stratigraphic correlation between the outcrop area and the covered area, the division and correlation of lithostratigraphic units and sequence stratigraphic units in covered area, the planar distribution and the vertical evolution of the sedimentary facies, the identification of sand reservoir in three-dimensional sesmic area in Tazhong area and the distribution and environmente of Permian volcanic eruption have been analyzed. In addition, the palaeosalinity analysis of mudstone was conducted. Based on the works mentioned above, the relationship between the palaeosalinity and sea level changes, sedimentary environment have been discussed. The main conclusion was appended below.1) The contrasted relationship between the field outcrops around Xiaohaizi in Bachu, Sishichang in Akesu and the covered area is clear.2) Most of the permian strata have obvious quartered characteristic. It is composed of the lower mudstone and limestone interbedded section in Nanzha Formation and the upper three retrogradation intervals of natural gamma ray logs. In the permo-carboniferous period, it totally have five times of the sea level changing processes in the Tarim Basin, each processe formed different lithologic sequence.3) Mudstone Section and Limestone Section of carboniferous system mainly was deposited in shelf to platform to lagoon and to tidal flat enviroment. But Sandstone and Mudstone Section in Kalashayi Formation mainly was deposited in river to delta enviroment. The clastic rock section of lower Permian system is a shelf to lagoon and tidal flat deposition in the middle and west of the basin, in the east is mainly a river to delta deposition; The upper Permian strata is mainly alluvial fan to river deposition.4) The sand body in Sandstone and Mudstone Section, Kalashayi Formation takes the shape of flower-shaped distribution of the delta deposition from the southeast in the three-dimensional seismic area of Tazhong area. The delta consists of some distributary channels.5) The Permian volcanic rocks are thicker over the areas from the west of Bachu to the east of Tazhong to Manjiaer. The volcanic rocks of Kaipaizileike Formation are accumulated further northeast compared to that of Kupukuziman Formation. Over the middle to west region of Tarim basin the volcanic rocks might have formed underwater.6) The range of palaeosalinity of water environment when the Carboniferous-Permian mudstone was deposited is 4.7%o-33.9%o, and display that the majority of mudstone samples show semi-saltwater sedimentary environment and freshwater-brackish environment is secondary while saltwater environment is less. Palaeosalinity of water environment when Carboniferous-Permian mudstone was deposited has a good correlation with eustacy and sedimentary facies evolution in this period. Because of multiple cycles of sea-level changes in carboniferous system, carboniferous strata consists of limestone and mudstone interbedded in vertical,these mudstone was mainly formed in sedimentary environment in which sea level is relatively in fall or slow rise and palaeosalinity is relatively low.