The Sequence Stratigraphic Frame Works And Depositional Facies Of The Lower Paleozoic In The Northeast Of Tarim Basin

Tarim Basin, as the biggest onshore petroliferous sedimentary basin in China, with an area of 560×103 km2, is very important in the development of western China. The structural patterns of Tarim Basin varied a lot in different geological stages. The frequent uplift and subsidence in the stress field of early pullapart and later extraction resulted in the congruence basin of nowadays. Therefore, it's necessary to systematically analyze the evolvement of structure, deposition and infill to find out the geological rules of Tarim Basin. This thesis studied the sequence stratigraphy frame of the lower Paleozoic group in the northeast of Tarim. On the basis of outcrops, cores, logs and seismic data, under the guidance of sequence stratigraphy, sedimentology and seismic stratigraphy, after building up the of sequence stratigraphy frame, the log facies and the seismic facies were studied in details, and then the deposition and infill pattern were analyzed to work out the distribution of sedimentary facies and the pattern of structural –deposition, which revived the infill and the deposition characters. The result of the thesis provided theoretical basis and pattern for future petroleum exploration in this area. The core of this thesis included the following contents: (1) The investigation of three outcrops in Yaerdang Mountain, Queerqueke Mountain and Yuanbao Mountain showed that, the studied area was in bathyal sea in Cambrian period. The middle and upper Ordovician was characterized by clastic rock of turbidity facies in bathyal sea. The Silurian was mainly medium sand, fine sand, siltstone and pelitic siltstone in shallow sea. Three sedimentary sequences can be concluded from the outcrops, turbidity sedimentary sequence, delta sedimentary sequence and tide flat sedimentary sequence. (2) There are two I level sequences, four II level sequences and 14 III level sequences in lower Palaeozoic group. The I level and II level sequence boundaries are obvious territorial unconformity surfaces; the III level sequence boundaries are partial unconformity surfaces or conformities. The sequence boundaries can be divided into 4 types: orogenesis and erosion unconformity, uplift and erosion unconformity, marine transgression and onlap unconformity, and onshore exposure unconformity. The characters and genesis of every type were analyzed in the thesis.