| Nihewan basin is a famous site which distribute many world ancient human sites.Oriental human had lived here from two million years ago to five thousand years ago, there has a continuous cultural heritage. Nihewan is accepted as the standard Quaternary strata,its integrity of strata exceed Villafranchian.Nihewan basin is located in Yangyuan country, Zhang Jiakou city. Its tectonic setting is in the northerst of Fen-Wei graben, the centra of North China plate, it adjacent to the western Shanxi-Erdos landmass and Jin-Ji landmass. Nihewan basin is formed by extensional rift from late Pliocene to the early Pleistocene, its fault structure develops well.Main goal of this paper is to investigate the tectonic evolution characteristics of Nihewan basin and its deep formation mechanism, at the same time, combining with Majuangou human site and typical sections to discuss the environmental evolution of Nihewan basin. Through tectonic evolution and environmental evolution research of Nihewan basin, it could provide huge basic geological data to other related disciplines in Nihewan basin, and has important theoretical and practical significance.To the aspect of tectonic evolution, it mainly combinated indoor organization of data with field exploration, and combinated geological background of Fen-Wei graben with Datong volcanic action, and discussed characteristics and deep formation mechanism of deep piedmont fault, as a result, it put forward a formation model of Nihewan basin. To the aspect of environmental evolution, it mainly combinated field sampling with indoor sample analysis, and combinated Majuangou human site and many other relevant typical sections,it has carried on preliminary discussion of environmental evolution of Nihewan basin in this paper.Through indoor and field research, consider that the formation, development and evolution of deep piedmont fracture of Nihewan basin has close relationship with Zhangxuan mantle branch, Fuping mantle branch and Datong volcanos. The formation,development and evolution of Zhangxuan mantle branch and Fuping mantle branch during Mesozoic era formed distribution pattern of deep piedmont fracture in the front of Xionger mountains and Liuleng mountains, also laid the foundation of Nihewan basin. Since the formation of Nihewan basin, the influence of Fen-Wei graben and Datong volcano is biggerthan Zhangxuan mantle branch and Fuping mantle branch. Mantle branch structure not only builded the foundation of structural framework in Nihewan basin, but also provided powerful motivation for the formation of Nihewan basin.Combining with the result of micropaleontology research in Majuangou human site,summarizing predecessors’ research materials, it considers that the environmental evolution in Nihewan basin can be divided into four stages: the first stage, Nihewan basin has yet to form a stable living conditions for water and ostracoda; the second stage, the water area in Nihewan basin increased to stability, the water has a certain of salty; the third stage, the scope of ancient lake basin reach maximum, sedimentary environment mainly controlled by lake facies, the scope of ancient lake basin started to shrink, the climate changed from warm-cold to semi-arid; the fourth stage, the water of ancient lake basin became much salty,the climate continuous vonvert to semi-arid even drought, and finally dried up. |
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