The Study Of Sedimentary Evolution And Structure Simulation In Peiku Co Basin, Tibet

Peiku Co Basin is in the Southern Tibet Valley between the Himalayas and Gangdise Mountain, which is a Late Cenozoic fault basin. Basin basement is composed of the Mesozoic fold stratum. There is a set of the Early Pleistocene to the Holocene fluviatile-lacustrine facies sedimentary stratum, and is known as one of the most complete and the thickest stratum in Quaternary Period sedimentary in Southern Tibetan Valley.Peiku Co Basin is one of later Cenozoic fore-mountain basin that is formed when the Himalayas collides the interior of the orogenic belt. Therefore, the sedimentary evolution and structure of Peiku Co basin must be inevitably related with the formation and the development of Himalayan formation. The study is centered on field investigation, carried out the sedimentary stratigraphy, tectonic geomorphology, basin fault, tectonic stress field, Paleoenvironmental, uranium, ESR and other sedimentary chronology study. The study is centered on the sedimentary evolution and nature of fault. Thus understand the basin evolution, discusses the relationship of the basin evolution and Himalaya uplifting and its response to environmental significance. The main conclusion as follows:1. Peiku Co Basin can be divided into 2 facies which is composed of alluvial, lacustrine, facies, 3 subfacies and 3 sedimentary system domains: water forward system,lake expansion system,lake contraction system. The result is basing on the detailed observation outcrop section and systematic working on samples, carrying on sedimentary system characteristics and the analysis of sedimentary facies;2. On the sedimentary characteristics, sequence stratigraphy, climate, source of supply, the analysis of deposit and integrated information of outcrop basis, it is working on division. Peiku Co basin can be divided into 1 Group: Peiku Co Group; 4 groups: Early Pleistocene Layang group, Central Pleistocene Mangjiadong group, Late Pleistocene Bangrong group and Holocene Luomarenbu group. It is first time that complete Quaternary lacustrine sedimentary profile is founded in Southern Tibet Valley;3. The evolvement of the Peiku Co Basin can be divided into three phases: Initial fault depression phase (Layang and Mangjiadong Group), fiercely fault depression phase (Bangrong formation 1 rock segment), stable stage (Bangrong formation 2-3 rock segment and Luomarenbu Group);4. Discussing the controlling factors of Peiku Co Basin formation and evolution. The study indicates that the formation and sedimentary space of Peiku Co basin is clearly controlled by south and north fault, and taking the view that the Peiku Co basin is a alice plated—dustpaned faulted basin;5. Use of SRTM datas, by analysising the basin regional tectonic geomorphology, the distribution from west to east of lacustrine sediment is controlled by the main tectonic activity, and the landscape of residue lake is controlled by N-S—direction minor tectonic activity;6. By finite element numerical simulation analysis, the results show that Peiku Co Basin's formation and its development obviously controlled by the boundary faults with the basin on both sides. Peiku Co Basin's formation was a result of different blocks' discrepant uplifting at the processe of the whole compressional stress of SN trending. The basin-controlling faults on the south are north-inclined normal faults, and on the north are south-inclined thrust faults,both of them compose the seesaw type tectonic downfaulted basin's movement process which characteristics is descends toward the south and increase toward the north.