摘要
根据野外考察、粒度分析及历史文献资料,研究了西安北郊草店村剖面在距今900~660 a形成的渭河漫滩沉积和洪水变化。结果表明,在距今900~660 a形成的草店村剖面洪水沉积分层明显,能够指示洪水事件和洪水深度。草店村剖面洪水沉积厚度为5.25 m,可划分为26个沉积层,指示了26次规模不同的洪水事件。洪水沉积厚度和粒度成分显示,草店村剖面的26个洪水事件发生时河漫滩上的洪水深度均大于2.2m;剖面下部第17~第26层沉积时漫滩上的洪水深度为4.0~7.0 m,河床水深为6.2~8.5 m;中部第8~第16层沉积时漫滩上的洪水深度为3.0~5.0 m,河床水深为6.6~9.0 m左右;上部第1~第7层沉积时漫滩上的洪水深度为2.2~3.0 m,河床水深为7.2~8.6 m。草店村剖面中部和下部的洪水沉积以中砂和细砂为主,剖面上部以粉砂和极细砂为主,指示的洪水规模比距今120 a来西安渭河洪水显著大。草店村剖面中的第12、16~26层代表的是特大洪水事件。西安北郊渭河在距今900~660 a发生的大洪水主要是由当年降水量的明显增加引起的。
Objectives： The purpose of the study is to reveal the scale and the depth of floods in historical periods, so that to provide a scientific basis for the prediction of flood scale and toreduce the losses caused by flood disasters. Methods ： Methods used in the study are field investigation, grain - sizedistribution analyses and compilation of historical data. Results： The flood deposition of the study section,lying in Caodian Village at northern suburb of Xi＇ an, was formed during 900 to 600 years ago. It is 5.25 meters thick and can be divided into 26 layers. It has a significant reflection and resolution on the occurrence of floods and short - term change of precipitation, andan indication of the frequency and depth of floods. There are some special characteristics of the floodplain sediments in this section, including coarse grain composition, high content of medium sand and fine sand, and less content of clay and silt. The content of colloidal particles（ 〈0. 002ram） ranges from 1.15% to 8.03% with an average of 3.33%. The average content of clay particles（0. 002 -0. 005mm） is 4.29% , ranging from 2.12% to 8.61%. The fine silt （0. 005 ~0.01mm） content ranges from2.52% to 11.14%, with an average content of 4.85%. Coarse silt（0.01 -0. 05mm） has a high content but great rangefrom9.89% to 62.33% , with an average of 22.14%. There is a certain amount of very fine sand（0.05 -0.10 mm） in each layer, ranging from2.19% to 30.88% with an average content of 9.32%. The content of fine sand （0. 10 -0.25mm） ranges greatlyfrom0.52% ~ 37.08%, with an average content of 19.46%. The content of medium sand （0.25 ~ 0.50 mm） is high but, again, ranges greatly from 0 to 46.64% with the average 27.07%. The content of coarse sand（0.50 -2.00 mm） changes rapidly from 0 to 26.11% , with an average content of 8.67%. The content of gravel（ 〉 2.00 mm） is very small in the whole profile, and only appears in the 18th, 19th, 22nd, 23rd, 2dth and 26th layers. And they display a maximum content of 0.30% and with an average of 0.03%. Conclusions： The sediment records 26 flood events onWeihe River in the northern suburb of Xi＇ an between 900 and 660 years ago. According to the thickness and grain - size distribution of flood sediment, the flood depth over the floodplain and the river bed was about 4 - 7 m and 6.2 - 8.5 m respectivelywhen the 17th - 28th layers formed. When the 8th - 16th layers occurred, the flood depth over the floodplain and the river bed were 3 -5m and 6.6 -9.0mrespectively. When the 1st ~7th layers occurred, the flood depth over the floodplain and the river bed was 2.2 - 3.0m and 7.2 - 8.6mrespectively. And it indicates that the floodof WeiheRiver at that time in the study area was significantly greater than it was in recent 120a. Among the layers, the 12th and 16th -28th layers represented extraordinary flood events. And fundamentally, between 900 and 660 years ago, the great flood occurring at WeiheRiver in the northern suburb of Xi＇ an mainly resulted from a significant increase in precipitation. After a full considerationof the grain - size distrihutiondue to the increase floodplain topography and the variation of deposit thickness, the order of the flood depth and scale of the riverbed flood in the 26 flood events of the seetion can be determined as follows： the 17th flood 〉 the 19th flood 〉 the 18th flood 〉 the 12th flood 〉 the 10th flood 〉 the 16th flood 〉 the 23th flood 〉 the 14th flood 〉 the 15th flood 〉 the 21th flood 〉 the 20th flood 〉 the 22th flood 〉 the 25th flood 〉 the 26th flood 〉 the 24th flood the 〉9th flood 〉 the 8th flood 〉 the llth flood 〉 the 13th flood 〉 the 2nd flood 〉 the 4th flood 〉 the 3rd flood 〉 the 1st flood 〉 the 7th flood 〉 the 5th flood 〉 the 6th flood.
出处
《地质论评》
CAS
CSCD
北大核心
2017年第2期326-336,共11页
Geological Review
基金
中国地质调查局西安地质调查中心"关中盆地第四系形成与演化"地质调查项目(编号:水[2016](4))
国家自然科学基金国际合作项目(编号:41210002)
中国科学院黄土与第四纪地质国家重点实验室项目(编号:SKLLQG1626)的研究成果~~
关键词
河漫滩沉积
洪水事件
洪水深度
洪水成因
西安渭河
sediment on floodplain
flood event
flood depth
flood causes
Weihe river in Xi＇an
