Geomorphology And Cenozoic Source Analysis Of The Jingtai Section Of The Upper Yellow River Basin

The Yellow River developed in the northeast margin of the Qinghai-Tibet Plateau,with strong geological dynamics and active geological structure in the basin.The dating of the three Yellow River terraces in Mijia Mountain,Chemuxia Gorge and Heishanxia Gorge shows that the Yellow River was first formed in the early Pleistocene.In the Qingtongxia Gorge,a large number of Pliocene Ganhegou formation strata related to the sediments of the Yellow River were deposited,indicating that the Yellow River reached the Qingtongxia Gorge in the Pliocene.At present,Pleistocene-Pliocene strata are developed near the Yellow River channel in Jingtai,and the source of these sediments may be related to the deposition of the Yellow River.Most of the predecessors studied the evolution of the Yellow River basin from the aspects of provenance and terrace,but there were few studies on the geomorphological evolution of the Yellow River basin in Jingtai.On the basis of geological survey,this paper uses remote sensing technology to extract geomorphological parameters of Jingtai area,analyzes regional topographic and geomorphological features,and discusses the source of sediments in the Yellow River basin of Jingtai area by means of clastic zircon and heavy minerals.In this paper,six kinds of basic topographic factors are extracted: slope,topographic fluctuation,surface cutting,surface outburst,surface roughness and elevation variation coefficient.The results show that the Jingtai region as a whole shows the characteristics of low slope and low terrain undulation,and the topographic undulation changes significantly in the local areas such as Haas Mountain and Mijia Mountain.The formation of the present geomorphological pattern in Jingtai area is related to the fault and the development of the Yellow River system.On the basis of the extraction of the river network,16 main tributaries are selected to analyze the longitudinal profile of the river.the results show that the development degree of the tributary water system on the east side of the Yellow River is higher than that on the west side of the river.The area-elevation integral values(HI)of 63 sub-basins are extracted and their spatial distribution characteristics are analyzed.The results show that the HI value of the west side of the Yellow River basin is higher than that of the east side of the basin,and the HI value is the highest near Mijia Mountain in the west side,indicating that the neotectonic activity in the west side of the basin is stronger than that in the east side of the basin.Through the analysis of heavy minerals,the heavy mineral assemblage of Gansu Group in the Yellow River basin in Jingtai area is composed of stable minerals,which is "garnet +hematite + ilmenite + magnetite + epidote + quartz,feldspar and altered minerals".The ZTR index is high,indicating the long-distance transport of the Yellow River.The peak ages of clastic zircons are mainly 200～300Ma,400～500Ma and 1700～2000Ma,which are consistent with the age characteristics of modern Yellow River sediments.In a word,it can be concluded that there are differences on both sides of the Yellow River in Jingtai from the analysis of topographic factors,the morphological characteristics of the longitudinal section of the tributaries and the elevation integral value of the sub-basin area.Through the analysis of the influence of lithology,climate and structure on the basin evolution,it is concluded that the tectonic activity is the main factor leading to the differential evolution between the east and west sides of the Yellow River.