Late Quaternary Paleoflood Hydrology At The Houtao Basin

The Houtao Basin is located in the transition zone between the eastern monsoon area and the western arid area.The Yellow River flows through the Kubuqi Desert and UlanBuh Desert,and a large amount of sand enters into the Yellow River,which makes the relationship between water and sand in this section of the river complicated.Under the influence of factors such as global change and human over-exploitation and utilization,the section of the river channel has been seriously silted in recent years,and potential flooding has become the greatest threat to people along the coast.Using sedimentary strata to obtain information on the evolution of long-scale rivers and changes in paleohydrology,and to grasp the occurrence of extreme hydrological events,can provide a certain scientific basis and theoretical basis for the construction of flood control projects and the development of water resources.This paper analyzes the grain size and elements of three drill cores(DKZ06,DKZ07,DKZ12)with a depth of about 20 m near the Yellow River in the Houtao Basin,under the chronological framework,the core sedimentary facies are divided and reconstructed,the paleoflood hydrology in the region since the late Quaternary was reconstructed and discuss the response of paleofloods to climate change.Obtain preliminary results:(1)The core sediments of DKZ06?DKZ07?and DKZ12 are mainly composed of sand,and their contents account for 65.3%?76.7%?and 64.3%.By analyzing the characteristics of particle size parameters and mechanical composition in different modern sedimentary environments,the relationship between sediment particle size characteristics and sedimentary environment is established,and then the sedimentary facies of the drilled core are divided.It is found that all three cores are based on the river sedimentary environment Mainly,the sedimentary thickness of the river bed facies is 14.37 m,16.84 m,13.25 m deep respectively,accounting for 72%,83% and 63% of the total.(2)In order to achieve the unity of the environmental index comparison,this paper mainly takes riverbed sediments as the research object,and extracted the average particle size,the percentage of sand(particle size greater than 63?m)and P95(the particle size at 95% on the frequency accumulation curve)as a proxy indicator of the grain size of the paleoflood.At the same time,the study found that the sediment ln(Si/Al)and the particle size index showed a good positive correlation,and then selected ln(Si/Al)as an indicator of paleofloods to obtain high-resolution paleohydrological information.(3)Supported by OSL chronology,the paleofloods recorded in the core of the at the Houtao Basin since the late Quaternary have 6 high-frequency periods and 5 low-frequency periods,namely 30-22ka?20.9-16ka? 13.8-12ka?11.7-9.5ka?7.5-5ka?3.9-1.4ka flood activities are frequent.By comparing with regional climate data,it is found that humid climate and more precipitation are the main reasons for the frequent and greater intensity of paleofloods.