| Synthesizing the analysis of outcrop sections, cores, well logs and seismic data, applying the theory and methods of sequence stratigraphy, modern sedimentology, and seismic stratigraphy, the sequence stratigraphy and depositional system of the Silurian in the Tarim basin were systematically researched and analyzed. The main results and understandings are as follows:Sequence boundary identification and characterization were developed, combined with the contact between the upper and lower of the key seismic stratigraphic sequence boundary, integrated by the filling evolution and the palaeo-geomorphic research of the basin, the three level sequence stratigraphic framework of Paleozoic Silurian in Tarim Basin was established. The Silurian is divided into two second-order sequences, four third-order sequences and eight system tracts, in where three genetic types of sequence boundary were identified. In the third-order sequence stratigraphic framework, the stacking patterns, conversion patterns and distribution area of stratigraphy were analyzed ,the context characteristics of the system tracts in different sedimentary environment were summarized, the sequence stratigraphic patterns of the tidal flat, coastal and brainded rive delta were constructed, and the spatial distribution law and evolution of different systems tracts were discussed. It is concluded that there are three sequences constitutes including rising base-level transgressive, stable base-level aggradational and downing base-level progradational parasequence sets. According to the comparison and analysis of features of the sequence stratigraphic framework of the study area, it is summarized that formation and development of sequence stratigraphy are controlled by the three elements:tectonic subsidence, changes of lake level, and paleoclimatic.According to the causes of sedimentary facies and identification marks, four depositional systems were identified in Paleozoic Silurian Tarim Basin, which were tidal flat, coastal,braided-river delta and shallow shelf, etc. Within the sequence stratigraphic framework,different types of depositional systems,characteristics of rock facies, facies sequence, facies composition, and stacking parttens of strata were analyzed, the depositional systems, the relation-ship of time, distribution area,characteristics of spatial distribution and Space-time evolution law were summarized. Types of sedimentary system and its component characteristics under the different depositional backgrounds within the sequence stratigraphic framework were discussed followed by its spatial distribution relationship research. Within the sequence stratigraphic framework, further summary for the evolution of various types of sand body was set up. It is shown that sq1 is mainly coastal depositional systems and a little tidal flat depositional systems in centre of Tarim, tidal flat depositional systems in Bacu, coastal depositional systems and shallow shelf in north part of Tarim, coastal depositional systems and brainded rive delta depositional systems in east part of Tarim, sq2 is mainly shallow shelf in north part of Tarim, shallow shelf and tidal flat depositional systems in centre of Tarim to Bacu, sq3 is mainly shallow shelf and tidal flat depositional systems, and a little coastal depositional systems in east and north part of Tarim, sq4 is mainly coastal depositional systems, and a little tidal flat depositional systems and brainded rive delta depositional systems somewhere, and there does not lie in north part of Tarim, there lies in coastal depositional systems and brainded rive delta depositional systems in east part of Tarim, totally. The transgressive systems tract were the coastal depositional systems , which mainly developed retrogradation accompanied by aggradation of Silurian in Tarim Basin. The high system tract were mainly the tidal flat depositional systems,which developed progradation accompanied by aggradation and erosion of Silurian in Tarim Basin.Through the northern Tarim Basin dating of zircon, suggesting that in the eastern part of the northern Tarim Basin provenance comes from Ordovician igneous rocks of Altun region, western part of the notthern Tarim Basin provenance comes from Precambrian basement of the northern Tarim Basin... |
PDF Full Text Request