全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于...全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于动物骨屑AMS ^(14)C年代数据,用Bacon程序拟合玉溪遗址剖面的沉积-年代关系,判定玉溪剖面古洪积层形成时段为约6.4 ka BP~7.3 ka BP。(2)古洪水沉积序列的粒度和端元分析结果显示,玉溪古洪积层由细粉砂-粉砂组成,表明古洪积层为溢岸憩流和滞水缓流堆积而成。(3)孢粉组合、磁化率、Rb/Sr和Si/Al比值等环境指标显示,玉溪剖面的古洪水沉积经历了早期湿热、中期温干、晚期暖湿三个阶段,其中古洪积层在温干阶段的沉积速率最大(30 cm·(100a)^(-1)),而且古洪水发生的频率亦高于湿热期。(4)古洪水沉积序列的小波功率谱分布特征表明,玉溪剖面的古洪水存在约30 a的短周期和约350 a的长周期;其长周期与区域性气候冷事件相关、短周期与ENSO事件导致的夏季风异常有关。本文提出的搬运洪积物的三种动力类型、干湿期古洪水的沉积速率差异以及古洪水泛滥的长短周期,对研究新石器早期重庆地区的人地关系和长江上游的洪水发生机制有参考意义。展开更多
Based on the detailed analyses,multi-proxies such as AMS 14 C dating,grain size,component and morphology of heavy minerals,micromorphology of zircon,magnetic susceptibility,Rb/Sr and Hg content are used to research th...Based on the detailed analyses,multi-proxies such as AMS 14 C dating,grain size,component and morphology of heavy minerals,micromorphology of zircon,magnetic susceptibility,Rb/Sr and Hg content are used to research the paleoflood sediments archived in the Yuxi Site.The research indicates that, since 7.6 kaBP,at least 16 times of paleoflood with water level above Wusong Elevation 147.024 m(a.s.l.) left deposits in the Neolithic layers of unit T0403 from the Yuxi Site.The results are induced from the following aspects:(1)The plaeoflood sediments take on great similarities with modern flood sediments in the Yuxi Site and Zhongba Site in probability cumulative curves which mainly show a pattern of 3 segments in fluvial pattern.(2)There is some resemblance between the heavy mineral components and the zircon shape characteristics of paleoflood deposits and those of modern flood deposits.(3) Magnetic susceptibility values(40.44―70.10SI)are lower than those of sediments from cultural layers (59.59―188.68SI).(4)Hg values(290.71―742.51 ng/g)are lower than those of sediments from cultural layers(344.16―10518.17 ng/g).(5)Rb/Sr values are higher than those of sediments from cultural layers, while those of the 4th,5th,6th,7th,8th cultural layers are high,which shows that they are inundated by paleoflood.The reason for many flood deposits existing is related to the site situated on the first terrace where the Yuxi River joins with the Yangtze River.As there are some similarities between the plaeoflood sediments and those of the Zhongba Site,it is feasible to confirm the existence of paleoflood sediments based on the above points.展开更多
The research of the paleoflood remains from archaeological sites is one of the most important jobs in the environmental archaeology.Based on the traditional archaeological methods and the archaeological finds from the...The research of the paleoflood remains from archaeological sites is one of the most important jobs in the environmental archaeology.Based on the traditional archaeological methods and the archaeological finds from the Yuxi site,Fengdu County of Chongqing,the paper analyzes the difference between the cultural layers and the possible paleoflood layers from various angles,such as contents,shapes of gravels,pottery,etc.,identifies the possible paleoflood deposit layers,i.e.the paleoflood remains of the Yangtze River,and discusses the periodicity of the floods.展开更多
Based on the principle that the present is the key to the past , detailed analyses, such as AMS 14C dating, grain size, component and morphology of heavy minerals, micro-morphology of zircon, Rb/Sr, magnetic susceptib...Based on the principle that the present is the key to the past , detailed analyses, such as AMS 14C dating, grain size, component and morphology of heavy minerals, micro-morphology of zircon, Rb/Sr, magnetic susceptibility and total organic carbon (TOC), were conducted to identify paleoflood sediments archived in Zhongba Site. The results indicate that the plaeoflood sediments bear great similarities with modern flood sediments in the following aspects: (1) probability cumulative curves mainly show a pattern of 3―4 segments; (2) grain-size distribution of suspended matter ranges between 3 and 10Ф; (3) the sediments are well-sorted, most of which are suspended matter (>50%); (4) the same species, quantity and morphology of heavy minerals; (5) scanning electronic microscope images show that shapes of zircon are mainly oval and nearly spheral, rounded due to long-distance transport; (6) higher Rb/Sr values (0.55―0.66)than those of sediments from cultural layers (0.03―0.26); (7) magnetic susceptibility values (133.73―433.05 10-6m3/kg) are lower than those of sediments from cultural layers (959.25―2442.44 10?6 m3/kg); (8) TOC (0.14%―0.33%) are lower than those of sediments from cultural lay-ers (1.13%―2.95%). Our results demonstrate that, except for the 1981 flood, there are at least six paleoflood events that occurred during the Qing Dynasty, the middle of Song Dy-nasty, the early Warring States (400BC―350BC), the West Zhou Dynasty (920BC―900BC), the Xia Dynasty (2070BC―1600BC), and the late Neolithic Age (3000BC―2300BC), respectively .展开更多
通过对黄河源区玛曲段河谷开展野外考察,在太吾若(TWR)发现典型的古洪水滞流沉积剖面。根据野外沉积学宏观特征判别,并结合粒度分布、磁化率、地球化学元素和石英颗粒微形态特征等室内实验分析测定结果,准确鉴别出TWR剖面所夹一组多层...通过对黄河源区玛曲段河谷开展野外考察,在太吾若(TWR)发现典型的古洪水滞流沉积剖面。根据野外沉积学宏观特征判别,并结合粒度分布、磁化率、地球化学元素和石英颗粒微形态特征等室内实验分析测定结果,准确鉴别出TWR剖面所夹一组多层洪水滞流沉积物(SWD),属典型的河流洪水在高水位滞流环境下沉积的悬移质泥沙。结果表明,TWR剖面古洪水SWD和现代洪水SWD沉积学分类为沙质粉沙,现代土壤为黏土质粉沙,现代风成沙为中沙。古洪水SWD粒度自然分布频率曲线为正偏,呈单峰,主峰高且峰值集中,分选性良好。古洪水SWD和现代洪水SWD磁化率较低,介于现代土壤和现代风成沙之间,化学元素明显区别于现代土壤和现代风成沙,表明它们尚未受到风化成壤作用影响,为古洪水悬移质快速沉积形成的滞流沉积物。石英颗粒微形态特征的分析表明,古洪水SWD和现代洪水SWD石英颗粒表面分布明显的三角痕、V形坑、撞击坑和凹面等水成沉积物的典型特征,属于河流沙类型。采用单片再生剂量法(SAR)光释光技术测年,证明在13.6~13.0 ka BP,黄河源地区经历了一期多次的大洪水事件,发生时段对应末次冰消期向全新世转折的时期,与欧洲和格陵兰冰芯记录末次冰消期中的Bolling/Aellrod暖期相对应,此时青藏高原地区冰川大规模消融,这期古洪水事件正是流域内冰融水大量下泄汇入黄河而形成的大洪水。展开更多
文摘全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于动物骨屑AMS ^(14)C年代数据,用Bacon程序拟合玉溪遗址剖面的沉积-年代关系,判定玉溪剖面古洪积层形成时段为约6.4 ka BP~7.3 ka BP。(2)古洪水沉积序列的粒度和端元分析结果显示,玉溪古洪积层由细粉砂-粉砂组成,表明古洪积层为溢岸憩流和滞水缓流堆积而成。(3)孢粉组合、磁化率、Rb/Sr和Si/Al比值等环境指标显示,玉溪剖面的古洪水沉积经历了早期湿热、中期温干、晚期暖湿三个阶段,其中古洪积层在温干阶段的沉积速率最大(30 cm·(100a)^(-1)),而且古洪水发生的频率亦高于湿热期。(4)古洪水沉积序列的小波功率谱分布特征表明,玉溪剖面的古洪水存在约30 a的短周期和约350 a的长周期;其长周期与区域性气候冷事件相关、短周期与ENSO事件导致的夏季风异常有关。本文提出的搬运洪积物的三种动力类型、干湿期古洪水的沉积速率差异以及古洪水泛滥的长短周期,对研究新石器早期重庆地区的人地关系和长江上游的洪水发生机制有参考意义。
基金Supported by the National Natural Science Foundation of China(Grant No.90411015)the National Science and Technology Support Project(Grant No.2006BAK21B02)+3 种基金the University Doctoral Foundation(Grant No.20050284011)the Foundation of Important Basic Research at Nanjing University(Grant No.0209005206)the Open Foundation of the State Key Laboratory of Loess and Qua-ternary Geology from the Institute of Earth Environment,CAS(Grant No.SKLLQG0503)the Physical Geography of"985"Items and the Test Foundation of Modern Analyses Center of Nanjing University(Grant No.0209001309)
文摘Based on the detailed analyses,multi-proxies such as AMS 14 C dating,grain size,component and morphology of heavy minerals,micromorphology of zircon,magnetic susceptibility,Rb/Sr and Hg content are used to research the paleoflood sediments archived in the Yuxi Site.The research indicates that, since 7.6 kaBP,at least 16 times of paleoflood with water level above Wusong Elevation 147.024 m(a.s.l.) left deposits in the Neolithic layers of unit T0403 from the Yuxi Site.The results are induced from the following aspects:(1)The plaeoflood sediments take on great similarities with modern flood sediments in the Yuxi Site and Zhongba Site in probability cumulative curves which mainly show a pattern of 3 segments in fluvial pattern.(2)There is some resemblance between the heavy mineral components and the zircon shape characteristics of paleoflood deposits and those of modern flood deposits.(3) Magnetic susceptibility values(40.44―70.10SI)are lower than those of sediments from cultural layers (59.59―188.68SI).(4)Hg values(290.71―742.51 ng/g)are lower than those of sediments from cultural layers(344.16―10518.17 ng/g).(5)Rb/Sr values are higher than those of sediments from cultural layers, while those of the 4th,5th,6th,7th,8th cultural layers are high,which shows that they are inundated by paleoflood.The reason for many flood deposits existing is related to the site situated on the first terrace where the Yuxi River joins with the Yangtze River.As there are some similarities between the plaeoflood sediments and those of the Zhongba Site,it is feasible to confirm the existence of paleoflood sediments based on the above points.
基金Supported by the Key Project of the National Natural Science Foundation of China(Grant No.90411015)the University Doctoral Foundation(Grant No.20050284011)+2 种基金the Foundation of Important Basis Research at Nanjing University(Grant No.0209005206)the Open Foundation of the State Key Laboratory of Loessand Quaternary Geology from the Institute of Earth Environment,CAS(Grant No.SKLLQG0503)the Physical Geography of‘985’Items and the Test Foundation ofModern Analyses Center of Nanjing University(Grant No 0209001309)
文摘The research of the paleoflood remains from archaeological sites is one of the most important jobs in the environmental archaeology.Based on the traditional archaeological methods and the archaeological finds from the Yuxi site,Fengdu County of Chongqing,the paper analyzes the difference between the cultural layers and the possible paleoflood layers from various angles,such as contents,shapes of gravels,pottery,etc.,identifies the possible paleoflood deposit layers,i.e.the paleoflood remains of the Yangtze River,and discusses the periodicity of the floods.
基金supported by the Key Project of the National Natural Science Foun-dation of China(Grant No.90411015)the National Natural Science Foundation of China(Grant No.40271103)+1 种基金Open Foundation of the State Key Laboratory of Loess and Quaternary Geology from the Insti-tute of Earth Environment,CAS(Grant No.SKLLQG0503)Physical Geography of“985”Item and Foundation of Modern Analyses Center of Nanjing University.
文摘Based on the principle that the present is the key to the past , detailed analyses, such as AMS 14C dating, grain size, component and morphology of heavy minerals, micro-morphology of zircon, Rb/Sr, magnetic susceptibility and total organic carbon (TOC), were conducted to identify paleoflood sediments archived in Zhongba Site. The results indicate that the plaeoflood sediments bear great similarities with modern flood sediments in the following aspects: (1) probability cumulative curves mainly show a pattern of 3―4 segments; (2) grain-size distribution of suspended matter ranges between 3 and 10Ф; (3) the sediments are well-sorted, most of which are suspended matter (>50%); (4) the same species, quantity and morphology of heavy minerals; (5) scanning electronic microscope images show that shapes of zircon are mainly oval and nearly spheral, rounded due to long-distance transport; (6) higher Rb/Sr values (0.55―0.66)than those of sediments from cultural layers (0.03―0.26); (7) magnetic susceptibility values (133.73―433.05 10-6m3/kg) are lower than those of sediments from cultural layers (959.25―2442.44 10?6 m3/kg); (8) TOC (0.14%―0.33%) are lower than those of sediments from cultural lay-ers (1.13%―2.95%). Our results demonstrate that, except for the 1981 flood, there are at least six paleoflood events that occurred during the Qing Dynasty, the middle of Song Dy-nasty, the early Warring States (400BC―350BC), the West Zhou Dynasty (920BC―900BC), the Xia Dynasty (2070BC―1600BC), and the late Neolithic Age (3000BC―2300BC), respectively .
文摘通过对黄河源区玛曲段河谷开展野外考察,在太吾若(TWR)发现典型的古洪水滞流沉积剖面。根据野外沉积学宏观特征判别,并结合粒度分布、磁化率、地球化学元素和石英颗粒微形态特征等室内实验分析测定结果,准确鉴别出TWR剖面所夹一组多层洪水滞流沉积物(SWD),属典型的河流洪水在高水位滞流环境下沉积的悬移质泥沙。结果表明,TWR剖面古洪水SWD和现代洪水SWD沉积学分类为沙质粉沙,现代土壤为黏土质粉沙,现代风成沙为中沙。古洪水SWD粒度自然分布频率曲线为正偏,呈单峰,主峰高且峰值集中,分选性良好。古洪水SWD和现代洪水SWD磁化率较低,介于现代土壤和现代风成沙之间,化学元素明显区别于现代土壤和现代风成沙,表明它们尚未受到风化成壤作用影响,为古洪水悬移质快速沉积形成的滞流沉积物。石英颗粒微形态特征的分析表明,古洪水SWD和现代洪水SWD石英颗粒表面分布明显的三角痕、V形坑、撞击坑和凹面等水成沉积物的典型特征,属于河流沙类型。采用单片再生剂量法(SAR)光释光技术测年,证明在13.6~13.0 ka BP,黄河源地区经历了一期多次的大洪水事件,发生时段对应末次冰消期向全新世转折的时期,与欧洲和格陵兰冰芯记录末次冰消期中的Bolling/Aellrod暖期相对应,此时青藏高原地区冰川大规模消融,这期古洪水事件正是流域内冰融水大量下泄汇入黄河而形成的大洪水。
