对汉江上游弥陀寺发现的完整黄土-古土壤剖面进行了沉积学特征以及磁化率、粒度、烧失量和w(Rb)/w(Sr)等气候替代性指标的分析及研究,结果表明:弥陀寺剖面自下而上具有马兰黄土(L_1)→过渡层黄土(L_t)→古土壤层(S_0)→近代黄土(L0)→...对汉江上游弥陀寺发现的完整黄土-古土壤剖面进行了沉积学特征以及磁化率、粒度、烧失量和w(Rb)/w(Sr)等气候替代性指标的分析及研究,结果表明:弥陀寺剖面自下而上具有马兰黄土(L_1)→过渡层黄土(L_t)→古土壤层(S_0)→近代黄土(L0)→表土层(TS)地层序列,记录了自晚更新世以来的气候变化;不同地层单元之间风化成壤差异显著,古土壤层(S_0)的风化成壤强度明显高于其它地层,马兰黄土(L1)的风化成壤强度最弱。剖面风化成壤强度的变化揭示了自马兰黄土堆积以来记录的气候变化,马兰黄土形成时期气候干燥寒冷,过渡层黄土的存在则说明气候由干冷向暖湿转变,古土壤层形成时期气候最为温暖湿润,近代黄土形成时期气候由暖湿向干冷转变。此外,弥陀寺剖面还记录了在全新世大暖期期间的一次气候变冷事件,结合光释光(OSL)测年数据,确定此事件发生于6.48 ka BP左右。展开更多
对若尔盖盆地进行实地考察,选取盆地西端黄河出口段典型的一级阶地沉积序列为研究对象。通过沉积物粒度和端元特征分析及OSL测年断代,对若尔盖盆地出口段的环境变化进行研究。研究结果表明:阶地底部的河床相砂卵石与河漫滩沙层构成了二...对若尔盖盆地进行实地考察,选取盆地西端黄河出口段典型的一级阶地沉积序列为研究对象。通过沉积物粒度和端元特征分析及OSL测年断代,对若尔盖盆地出口段的环境变化进行研究。研究结果表明:阶地底部的河床相砂卵石与河漫滩沙层构成了二元结构沉积层,其中河漫滩沙层夹有5.0—4.2 ka B.P.期间堆积形成的浅洼地泥沼土透镜状层,表明该河段黄河一级阶地从5.0 ka B.P.开始形成。河漫滩上为高原强劲风力改造成的风沙层,夹有古洪水滞流沉积层组,表明4.2—4.0 ka B.P.期间气候恶化,黄河源曾发生多期特大洪水事件。4.0—2.8 ka B.P.期间气候湿润,阶地面浅洼地有淤泥质沼泽形成。其后沙尘暴搬运堆积的粗粉沙覆盖阶地面,形成了风成黄土,其上部经生物风化成壤改造,发育成为具有团粒构造的现代亚高山草甸黑土土壤层。展开更多
青海官亭盆地喇家遗址史前巨大灾难事件,是我国史前环境变化与文明演变研究领域的热点之一。通过对官亭盆地喇家遗址北侧大红山前古洪积扇前沿地带的野外考察,进行土壤沉积物地层划分、结合理化指标测试分析,发现该地带土壤与沉积物的...青海官亭盆地喇家遗址史前巨大灾难事件,是我国史前环境变化与文明演变研究领域的热点之一。通过对官亭盆地喇家遗址北侧大红山前古洪积扇前沿地带的野外考察,进行土壤沉积物地层划分、结合理化指标测试分析,发现该地带土壤与沉积物的基本层序,自下而上依次为晚更新世马兰黄土(L1)—全新世早期过渡性风成黄土(Lt)—全新世中期古土壤(S0)—全新世晚期风成黄土(L0)—现代耕作土壤(MS)。这个层序特点与黄河北岸第二级阶地喇家遗址区域相同,也与黄土高原地区全新世土壤沉积物的层序相同。在全新世中期黑垆土古土壤(S0)中夹有三层红色泥流沉积层(RC1、RC2、RC3),是全新世中期后段气候恶化条件之下,暴雨山洪泥流溢出沟槽在地面扩散沉积形成。该地带以RC1为代表第一期山洪泥流事件早于喇家遗址毁灭的年代。以RC2为代表的第二期山洪泥流层卷入密集的木炭屑和杂物,表明在山洪泥流发生的时候有火灾发生,这对应着3850 a B.P.毁灭喇家遗址的大地震和山洪泥流群发生灾难事件。以RC3为代表的第三期山洪泥流事件,与喇家遗址区域相同发生在3600 a B.P.。其后在古洪积扇前沿到黄河第二级阶地的范围,再没有发生山洪泥流溢出沟槽扩散覆盖土地并且毁灭聚落成灾的现象。在喇家遗址北侧古洪积扇区域建立了全新世土壤地层序列,分析了该地带山洪泥流与喇家遗址灾难事件的联系。这对于研究揭示史前时期以来官亭盆地人地关系演变具有科学意义。展开更多
对喇家遗址进行了全面的野外考察,在其北部发现完整连续的全新世黄土-古土壤地层剖面。通过系统采样、粒度和磁化率等多种指标测试,结合OSL技术测年断代,建立了完整的土壤地层序列。深入分析土壤沉积物性质与地表过程,揭示了覆盖齐家文...对喇家遗址进行了全面的野外考察,在其北部发现完整连续的全新世黄土-古土壤地层剖面。通过系统采样、粒度和磁化率等多种指标测试,结合OSL技术测年断代,建立了完整的土壤地层序列。深入分析土壤沉积物性质与地表过程,揭示了覆盖齐家文化废墟的沉积物的成因。研究结果表明:喇家遗址土壤沉积物地层层序自地表向下依次为:现代土壤(MS,0~1.50 ka B.P.)→全新世晚期风成黄土(L0,1.50~3.10 ka B.P.)→全新世中期古土壤(S0,3.10~8.50 ka B.P.)→全新世早期过渡性风成黄土(Lt,8.50~11.50 ka B.P.)→晚更新世晚期马兰黄土(L1,>11.50 ka B.P.)。其中全新世中期黑垆土古土壤(S0)被3组红色粘土质泥流(RC3、RC2和RC1)和山洪沙土(FFD)沉积层穿插分隔为4个亚层(S0上、S0中上、S0中下和S0下)。这证明黑垆土发育过程中,在OSL年龄3.96~3.65ka,对应于14C年龄3.85~3.60 ka B.P.出现一个山洪泥流盛行期,来自于盆地北侧沟谷的大规模暴雨山洪泥流,在大红山前古洪积扇前沿溢出沟槽、扩散覆盖了黄河第二级阶地面的土地。其中与大地震相伴随的第一期暴雨山洪泥流过程,摧毁了喇家遗址齐家文化聚落,造成居室内人群的死亡。展开更多
Optically stimulated luminescence （OSL） dating for polymlneral fine-grained loess samples, collected in Laoguantai （LGT） section on the south of the Chinese Loess Plateau, was made by application of single-aliquot...Optically stimulated luminescence （OSL） dating for polymlneral fine-grained loess samples, collected in Laoguantai （LGT） section on the south of the Chinese Loess Plateau, was made by application of single-aliquot regenerative-dose （SAR） protocol. A ＇Double-SAW procedure in which aliquots are subjected to both infrared （IR） and blue stimulations was used and two sets of equivalent dose （De） determinations were produced and assumed to relate predominantly to feldspathic and quartz fine grain populations respectively, The OSL ages estimated from IRSL signals are smaller than those estimated from [post-IR] OSL signals due to the anomalous fading of feldspar IR signals, based on fading experiment, The young ages of the samples near ground surface may be originated from the post-depositional disturbance by the intensifying humanity＇s cultivation since 3.0 ka BP in the Guanzhong Basin, south of the Chinese Loess Plateau. Based on OSL dating, as well as field observations and stratigraphic correlation, we determine the chronology of the LGT Ioess-paleosol sequence. In combination with climate proxy records, it is indicated that aeolian loess deposition and pedogenesis underwent polyphase changes during the Holocene, likely to have been driven by shifts in the East Asian monsoon. This suggests that aeolian loess deposition is episodic and highly variable, with contributions from non-aeolian processes such as alluvial deposition found in the area.展开更多
Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioe...Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site （GCZ）. These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence （OSL） dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.展开更多
对天水樊家城剖面的地层、磁化率、粒度、CaCO3等进行分析,探讨了该地区全新世环境演变与人类活动的关系。结果表明:黄土层中磁化率、<5μm黏粒含量和黏粉比值明显偏低,>50μm砂粒含量、CaCO3值明显偏高,而古土壤层中磁化率、黏...对天水樊家城剖面的地层、磁化率、粒度、CaCO3等进行分析,探讨了该地区全新世环境演变与人类活动的关系。结果表明:黄土层中磁化率、<5μm黏粒含量和黏粉比值明显偏低,>50μm砂粒含量、CaCO3值明显偏高,而古土壤层中磁化率、黏粒含量则达到峰值,>50μm砂粒含量、CaCO3值明显偏低,其风化成壤强度呈现出马兰黄土L1→过渡性黄土Lt→古土壤S0逐渐升高、全新世黄土L0降低的特征。它反映末次冰期结束后(?~8500 a B.P.),气候逐渐转暖转湿,但仍较干冷,动植物资源不足,难以满足人类的生存和发展的需求,研究区内人类活动的强度很弱。全新世中期(8500~3100 a B.P.),气候温暖湿润,人类活动强度增大,原始定居农业得到极大发展,普遍出现以大地湾文化、仰韶文化、马家窑文化、齐家文化为代表的人类文化;其中,6000~5000 a B.P.气候出现干凉化趋势,但该时期人类文化依然获得了发展。全新世晚期(3100 a B.P.以来),东亚季风格局发生转变,气候转为较干冷,致使区域自然环境发生变化,区内逐渐兴盛游牧文化。近代以来随着人口、生产力水平等因素的影响,人类活动对环境的影响持续增强,土地利用方式以农耕为主。展开更多
文摘对汉江上游弥陀寺发现的完整黄土-古土壤剖面进行了沉积学特征以及磁化率、粒度、烧失量和w(Rb)/w(Sr)等气候替代性指标的分析及研究,结果表明:弥陀寺剖面自下而上具有马兰黄土(L_1)→过渡层黄土(L_t)→古土壤层(S_0)→近代黄土(L0)→表土层(TS)地层序列,记录了自晚更新世以来的气候变化;不同地层单元之间风化成壤差异显著,古土壤层(S_0)的风化成壤强度明显高于其它地层,马兰黄土(L1)的风化成壤强度最弱。剖面风化成壤强度的变化揭示了自马兰黄土堆积以来记录的气候变化,马兰黄土形成时期气候干燥寒冷,过渡层黄土的存在则说明气候由干冷向暖湿转变,古土壤层形成时期气候最为温暖湿润,近代黄土形成时期气候由暖湿向干冷转变。此外,弥陀寺剖面还记录了在全新世大暖期期间的一次气候变冷事件,结合光释光(OSL)测年数据,确定此事件发生于6.48 ka BP左右。
文摘对若尔盖盆地进行实地考察,选取盆地西端黄河出口段典型的一级阶地沉积序列为研究对象。通过沉积物粒度和端元特征分析及OSL测年断代,对若尔盖盆地出口段的环境变化进行研究。研究结果表明:阶地底部的河床相砂卵石与河漫滩沙层构成了二元结构沉积层,其中河漫滩沙层夹有5.0—4.2 ka B.P.期间堆积形成的浅洼地泥沼土透镜状层,表明该河段黄河一级阶地从5.0 ka B.P.开始形成。河漫滩上为高原强劲风力改造成的风沙层,夹有古洪水滞流沉积层组,表明4.2—4.0 ka B.P.期间气候恶化,黄河源曾发生多期特大洪水事件。4.0—2.8 ka B.P.期间气候湿润,阶地面浅洼地有淤泥质沼泽形成。其后沙尘暴搬运堆积的粗粉沙覆盖阶地面,形成了风成黄土,其上部经生物风化成壤改造,发育成为具有团粒构造的现代亚高山草甸黑土土壤层。
文摘青海官亭盆地喇家遗址史前巨大灾难事件,是我国史前环境变化与文明演变研究领域的热点之一。通过对官亭盆地喇家遗址北侧大红山前古洪积扇前沿地带的野外考察,进行土壤沉积物地层划分、结合理化指标测试分析,发现该地带土壤与沉积物的基本层序,自下而上依次为晚更新世马兰黄土(L1)—全新世早期过渡性风成黄土(Lt)—全新世中期古土壤(S0)—全新世晚期风成黄土(L0)—现代耕作土壤(MS)。这个层序特点与黄河北岸第二级阶地喇家遗址区域相同,也与黄土高原地区全新世土壤沉积物的层序相同。在全新世中期黑垆土古土壤(S0)中夹有三层红色泥流沉积层(RC1、RC2、RC3),是全新世中期后段气候恶化条件之下,暴雨山洪泥流溢出沟槽在地面扩散沉积形成。该地带以RC1为代表第一期山洪泥流事件早于喇家遗址毁灭的年代。以RC2为代表的第二期山洪泥流层卷入密集的木炭屑和杂物,表明在山洪泥流发生的时候有火灾发生,这对应着3850 a B.P.毁灭喇家遗址的大地震和山洪泥流群发生灾难事件。以RC3为代表的第三期山洪泥流事件,与喇家遗址区域相同发生在3600 a B.P.。其后在古洪积扇前沿到黄河第二级阶地的范围,再没有发生山洪泥流溢出沟槽扩散覆盖土地并且毁灭聚落成灾的现象。在喇家遗址北侧古洪积扇区域建立了全新世土壤地层序列,分析了该地带山洪泥流与喇家遗址灾难事件的联系。这对于研究揭示史前时期以来官亭盆地人地关系演变具有科学意义。
文摘对喇家遗址进行了全面的野外考察,在其北部发现完整连续的全新世黄土-古土壤地层剖面。通过系统采样、粒度和磁化率等多种指标测试,结合OSL技术测年断代,建立了完整的土壤地层序列。深入分析土壤沉积物性质与地表过程,揭示了覆盖齐家文化废墟的沉积物的成因。研究结果表明:喇家遗址土壤沉积物地层层序自地表向下依次为:现代土壤(MS,0~1.50 ka B.P.)→全新世晚期风成黄土(L0,1.50~3.10 ka B.P.)→全新世中期古土壤(S0,3.10~8.50 ka B.P.)→全新世早期过渡性风成黄土(Lt,8.50~11.50 ka B.P.)→晚更新世晚期马兰黄土(L1,>11.50 ka B.P.)。其中全新世中期黑垆土古土壤(S0)被3组红色粘土质泥流(RC3、RC2和RC1)和山洪沙土(FFD)沉积层穿插分隔为4个亚层(S0上、S0中上、S0中下和S0下)。这证明黑垆土发育过程中,在OSL年龄3.96~3.65ka,对应于14C年龄3.85~3.60 ka B.P.出现一个山洪泥流盛行期,来自于盆地北侧沟谷的大规模暴雨山洪泥流,在大红山前古洪积扇前沿溢出沟槽、扩散覆盖了黄河第二级阶地面的土地。其中与大地震相伴随的第一期暴雨山洪泥流过程,摧毁了喇家遗址齐家文化聚落,造成居室内人群的死亡。
基金National Natural Science Foundation of China, No.40571154 No.40471119
文摘Optically stimulated luminescence （OSL） dating for polymlneral fine-grained loess samples, collected in Laoguantai （LGT） section on the south of the Chinese Loess Plateau, was made by application of single-aliquot regenerative-dose （SAR） protocol. A ＇Double-SAW procedure in which aliquots are subjected to both infrared （IR） and blue stimulations was used and two sets of equivalent dose （De） determinations were produced and assumed to relate predominantly to feldspathic and quartz fine grain populations respectively, The OSL ages estimated from IRSL signals are smaller than those estimated from [post-IR] OSL signals due to the anomalous fading of feldspar IR signals, based on fading experiment, The young ages of the samples near ground surface may be originated from the post-depositional disturbance by the intensifying humanity＇s cultivation since 3.0 ka BP in the Guanzhong Basin, south of the Chinese Loess Plateau. Based on OSL dating, as well as field observations and stratigraphic correlation, we determine the chronology of the LGT Ioess-paleosol sequence. In combination with climate proxy records, it is indicated that aeolian loess deposition and pedogenesis underwent polyphase changes during the Holocene, likely to have been driven by shifts in the East Asian monsoon. This suggests that aeolian loess deposition is episodic and highly variable, with contributions from non-aeolian processes such as alluvial deposition found in the area.
基金funded by the National Natural Science Foundation of China(41030637)the Science and Technology Project of Baoji City(14SFGG-2)+1 种基金the Fundamental Research Funds for Key Subject Physical Geography of Baoji University of Arts and ScienceShaanxi Province and the Key Library Program of Education Department of Shaanxi Province(15JS008)
文摘Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits （SWDs） was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site （GCZ）. These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence （OSL） dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.
文摘对天水樊家城剖面的地层、磁化率、粒度、CaCO3等进行分析,探讨了该地区全新世环境演变与人类活动的关系。结果表明:黄土层中磁化率、<5μm黏粒含量和黏粉比值明显偏低,>50μm砂粒含量、CaCO3值明显偏高,而古土壤层中磁化率、黏粒含量则达到峰值,>50μm砂粒含量、CaCO3值明显偏低,其风化成壤强度呈现出马兰黄土L1→过渡性黄土Lt→古土壤S0逐渐升高、全新世黄土L0降低的特征。它反映末次冰期结束后(?~8500 a B.P.),气候逐渐转暖转湿,但仍较干冷,动植物资源不足,难以满足人类的生存和发展的需求,研究区内人类活动的强度很弱。全新世中期(8500~3100 a B.P.),气候温暖湿润,人类活动强度增大,原始定居农业得到极大发展,普遍出现以大地湾文化、仰韶文化、马家窑文化、齐家文化为代表的人类文化;其中,6000~5000 a B.P.气候出现干凉化趋势,但该时期人类文化依然获得了发展。全新世晚期(3100 a B.P.以来),东亚季风格局发生转变,气候转为较干冷,致使区域自然环境发生变化,区内逐渐兴盛游牧文化。近代以来随着人口、生产力水平等因素的影响,人类活动对环境的影响持续增强,土地利用方式以农耕为主。
