重庆江北砾岩的砾石统计及其沉积环境探究  

The Gravel Statistics and Sedimentary Environment of Jiangbei Conglomerate in Chongqing

作　　者：张宜梅[1,2] 王建力[1,3] 钟俊 

机构地区：[1]西南大学地理科学学院,重庆400715 [2]重庆市潼南中学,重庆潼南402660 [3]西南大学三峡库区生态环境教育部重点实验室 [4]化学化工学院,重庆400715

出　　处：《重庆师范大学学报（自然科学版）》2013年第1期48-52,共5页Journal of Chongqing Normal University:Natural Science

基　　金：国家自然科学基金(No.40971122)

摘　　要：江北砾岩的砾组分析及其测年表明,重庆北碚西师附中剖面的江北砾岩在24.3 kaB.P.至10 kaB.P.期间,总体经历了细→粗→细两个沉积旋回。具体又可以细分为了7个小的粗→细的沉积旋回,在此基础上还叠加了更多更小尺度的粗、细变化,推测这些砾度的变化主要与气候干湿的频繁波动有关。研究发现重庆及其上游地区在24.3 kaB.P.至10kaB.P.期间爆发了7次古洪水,其中22.5 kaB.P.前后沉积了长轴为31 cm的砾石,由此推算此时的古洪水量达到约119 690.783 m3.s-1,为特大洪水量级,表明当时的水动力相当强;重庆及其上游地区在该时期降水强度达到最大,但是该层的厚度较小,推测此次强降水过程时间较短。研究认为,由于砾度有7次粗→细的过程,因此在24.3 kaB.P.至10 kaB.P.期间,重庆及其上游地区应该经历了7次降水多→少的过程,显示了24.3 kaB.P.至10 kaB.P.期间重庆及其上游地区降水强度变化较大。在相对湿润期降水充沛,河流水动力较强,更大砾径的砾石被洪水带至河漫滩或边滩沉积;反之在相对干旱期降水较少,河流水动力较弱,能被带至该地沉积的砾石砾径相对较小,许多细粒砂被带至此地沉积从而在砾岩中形成了许多砂岩或砂砾互层。The analysis of gravel group of Jiangbei conglomerate and dating shows that Jiangbei conglomerate of Xishi Fuzhong section has experienced two sedimentary spinning back,fine to thick and thick to fine.Concretely speaking,it can be divided into seven sedimentary spinning backs and each spinning back represents a flood period.Based on it more small scale of crude,fine changes,it is speculate that these changes of gravel is caused by frequently fluctuations of climate.According to the research,in Chongqing and upstream area,the ancient flood had been broken out seven times between 24.3 kaB.P.and 10 kaB.P.Among them in 22.5 kaB.P.sedimentary which reach 31 cm,according to the calculated.At this time,the ancient flood capacity amounts to about 119 690.783 m3·s-1.It shows that the water power was very strong at that time.But the layer is thick,so we speculated that the rainfall took a short time.In particularly,the gravel degree has seven times from thick to fine,so the precipitation may has seven times from more to less in Chongqing and upstream area between 24.3 kaB.P.and 10 kaB.P.It shows that precipitation intensity changes greatly in this time.Relatively wet period abundant precipitation,the water power is stronger;the big gravel can be taken to the beach and sedimentary by the flood.Otherwise,relatively dry period less rainfall,the water power is weak,it can only bring small gravel and sedimentary,much fine sand was taken to sedimentary and in formed many sandstone layers.

关 键 词：江北砾岩 沉积环境 砾组分析 重庆 

分 类 号：P512.22[天文地球—地质学] P588.2