六盘山北部寺口子砂岩沉积过程及其对区域环境和全球气候变化的响应

The appearance of the arid environments and yellow deserts of temperate zone in central Asia, which is represented by those arid environments and yellow deserts in northwest China, is an important environment-evolution event in global Cenozoic history. Its origin, evolution process and formation mechanism are significant scientific problems, faced by the international study of Cenozoic especially Quaternary geology in long term, and concerned by domestic and foreign scholars. Since the uplift of Qinghai-Tibet plateau and its environmental effects may be the primary cause of the event on great background of global tectonic movement and climate changes, that is to say, the uplift of Qinghai-Tibet plateau can increase both the monsoon rainfall in the east of China and the inland aridification in the northwest of china contemperily, Therefore, it causes the formation and development of temperate-arid environment and yellow desert of northwest inland, and the evidence of this process can be traced back to the end of the Oligocene(about 25Ma.BP). However, it is seriously necessary to find representative geological records to realize the conditions of the Paleogene.Lying in the northern part of Mt. Liupanshan at the northeastern edge of Qinghai-Tibet Plateau, as a famous positive stratotype section of Sikouzi Formation, Sikouzi sandstone in Guyuan city of Ningxia province is an ideal stratigraphic section of reconstruction of inland environment changes in the period. However, there are still serious arguments on its cause, hydraulic origin or eolian origin, which can not make a final conclusion on a series of problems such as its age, cause and environment. On the basis of precedent achievements, by researching on Sikouzi sandstone in detail, helped with investigation of Sikouzi Formation in the region, this study will ascertain its sedimentary age furtherly, clarify deposition facies, confirm genetic type, recover sedimentary process, reconstruct its paleoenvironment and evolution, approach its response mechanism to global environmental changes by comparing with the related records of geological environment and paleoclimate issues of regions and the world in the same period. This can help to resolve the problems of the cause and environment of the stratum Sikouzi Sandstone,and also can set up a typical inland sedimentary section of Paleogene, to promote the research on the record and paleoenvironment of Paleogene in inland area, to provide new evidence for the study about the tripling mechanism of Qinghai-Tibet plateau uplifting-monsoon changing-desert evolution,and also to play a promoting role in study about stratums similar to the Sikouzi sandstone.

古近纪内陆古环境重建是我国第四纪和新生代地质研究面临的前沿课题。位于青藏高原东北缘六盘山北部，作为著名寺口子组的正层型剖面，寺口子砂岩剖面是该期内陆环境变化重建的一个理想剖面。但其成因认识尚存在水成与风成两大分歧，以致其时代、成因、环境等一系列问题尚无定论。本项目拟在前人研究的基础上,通过对寺口子剖面进行野外调查与研究，厘定沉积时代、澄清沉积特征，揭示成因类型，恢复沉积过程，重建其古地理环境与演变过程，并与区域及全球有关地质环境及古气候事件记录进行对比，探讨其对全球气候环境演变的响应机理。本项研究有助于解决该地层的成因与环境问题，有望建立典型古近纪内陆沉积剖面，促进内陆古近系记录及其古环境研究，并为青藏高原隆升-季风变迁-沙漠演化等耦合机制研究提供新的证据，同时，对类似砂岩地层的研究具有一定的推动作用.