The Baxie loess section, just east of the Tibetan Plateau, contains evidence showing that the Asi... more The Baxie loess section, just east of the Tibetan Plateau, contains evidence showing that the Asian monsoon climate experienced an abrupt reversal near the end of the last glacial age. Rapid deposition of dust under cool, dry full-glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm, moist summer monsoon. A subsequent abrupt increase in dust deposition, a response to a weakening of the summer monsoon, was later followed by renewed soil formation as summer monsoon circulation again intensified during the early Holocene. By one interpretation, the thin upper loess is a manifestation of the European Younger Dryas oscillation; however, in this case the available 14C ages require either that (1) onset of loess deposition lagged the beginning of the Younger Dryas event in Europe by as much as 2000 calibrated 14C years or (2) all the 14C ages are too young, possibly due to contamination. Alternatively, the late-gla...
识别全新世气候事件、阐明其区域环境表现特征、揭示其驱动机制是理解气候系统变化行为、预测未来气候变化以及弄清考古学文化转变动因的关键，具有重要的科学价值和现实意义。随着高分辨率全新世古气候重建的进... more 识别全新世气候事件、阐明其区域环境表现特征、揭示其驱动机制是理解气候系统变化行为、预测未来气候变化以及弄清考古学文化转变动因的关键，具有重要的科学价值和现实意义。随着高分辨率全新世古气候重建的进展，7.5~7.0 cal.ka B. P.事件逐渐被揭示，但到目前为止仍缺乏针对该气候事件各种类型证据的系统收集、对比以及对其产生动力机制的分析。本文基于中国26条古气候记录，系统总结了这一气候事件在中国地区的环境表现。结果显示，7.5~7.0 cal.ka B. P.气候事件在中国多个地区都有明显的反映，整体表现为温度下降、夏季风强度减弱。与全球其他地区的古气候记录对比显示7.5~7.0 cal.ka B. P.气候事件可能具有全球性的特征。与驱动因子系列对比发现该气候事件发生在北半球夏季太阳辐射逐渐减少、太阳活动减弱、火山活动频发、劳伦泰德冰盖快速融化期间，表明这4种因素在7.5~7.0 cal.ka B. P.气候事件发生过程中发挥了作用。未来需要更多测年准确、分辨率高的古气候记录定量-半定量刻画该气候事件的变化幅度、起止时间以及区域差异，同时结合古气候模拟揭示7.5~7.0 cal.ka B. P.气候事件产生的动力机制。
Ocean drilling in the Bengal Fan has revealed the uplift history of the Himalayas and Indian mons... more Ocean drilling in the Bengal Fan has revealed the uplift history of the Himalayas and Indian monsoon,but there is no analogous deep-water fan in the Western Pacific marginal seas that can be drilled and used to constrain the Tibet uplift history from its eastern side.The Yangtze river,originating from northeastern Tibet and draining a large area prevailed by monsoon precipitation,is highly sensitive to plateau uplift and monsoon evolution.A systematical study of the Yangtze river deposits will test various hypotheses concerning plateau uplift and its link with monsoon evolution.Along the modern Yangtze river,the upper reach is decoupled from the lower reach by the Three Gorges.About 30% of the total sediment load from the Yangtze river is laid in the Jianghan Basin immediately out from the Gorges,~40% is deposited in the lower reach and delta,and only ~30% is transported to the East China Sea.Therefore,a combination of ocean and continental drilling along the Yangtze River will reco...
OSL dating of fine-grained quartz from Holocene Yangtze delta sediments Holocene flood events in ... more OSL dating of fine-grained quartz from Holocene Yangtze delta sediments Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail. In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4-11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by crosschecking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR 50 and pIRIR 160) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR 160 dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of 3 Gy ka-1). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ~6 ka between 9.65 and 5.50 m in core H1 and ~2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR 160 signals suggest less light exposure of the core top sediments and of those from the transition layer between ~6 ka to ~2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.
Hydroclimate variations associated with the East Asian Summer Monsoon (EASM) precipitation exert ... more Hydroclimate variations associated with the East Asian Summer Monsoon (EASM) precipitation exert significant impacts on lives of people inhabiting within the Yangtze River drainage and the coastal zone of South China. Seasonal shift of main precipitation area is attributable to the reposition of northern limit of summer monsoon, which would lead to provenance and composition changes of suspended materials transported by the Yangtze River. Consequently, the interannualto millennial -scale variability in the position of rain belt mentioned above could be recorded in the long-term change in compositional variation of the sediment originated from the suspended materials from the Yangtze River. The inner shelf sediments of the East China Sea (ECS) is of primary importance to study provenance changes of terrestrial materials from the Yangtze River. Because of this expectation, we examined provenance changes in MD06-3040 core sediments recovered from the inner shelf of ECS in association w...
A palaeomagnetic investigation of a late Quaternary loess-palaeosol sequence in central China has... more A palaeomagnetic investigation of a late Quaternary loess-palaeosol sequence in central China has revealed two episodes of anomalous geomagnetic field behaviour in the lower and upper parts of soil complex S1, which spans the last interglacial interval. Comparison of the ...
The Baxie loess section, just east of the Tibetan Plateau, contains evidence showing that the Asi... more The Baxie loess section, just east of the Tibetan Plateau, contains evidence showing that the Asian monsoon climate experienced an abrupt reversal near the end of the last glacial age. Rapid deposition of dust under cool, dry full-glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm, moist summer monsoon. A subsequent abrupt increase in dust deposition, a response to a weakening of the summer monsoon, was later followed by renewed soil formation as summer monsoon circulation again intensified during the early Holocene. By one interpretation, the thin upper loess is a manifestation of the European Younger Dryas oscillation; however, in this case the available 14C ages require either that (1) onset of loess deposition lagged the beginning of the Younger Dryas event in Europe by as much as 2000 calibrated 14C years or (2) all the 14C ages are too young, possibly due to contamination. Alternatively, the late-gla...
识别全新世气候事件、阐明其区域环境表现特征、揭示其驱动机制是理解气候系统变化行为、预测未来气候变化以及弄清考古学文化转变动因的关键，具有重要的科学价值和现实意义。随着高分辨率全新世古气候重建的进... more 识别全新世气候事件、阐明其区域环境表现特征、揭示其驱动机制是理解气候系统变化行为、预测未来气候变化以及弄清考古学文化转变动因的关键，具有重要的科学价值和现实意义。随着高分辨率全新世古气候重建的进展，7.5~7.0 cal.ka B. P.事件逐渐被揭示，但到目前为止仍缺乏针对该气候事件各种类型证据的系统收集、对比以及对其产生动力机制的分析。本文基于中国26条古气候记录，系统总结了这一气候事件在中国地区的环境表现。结果显示，7.5~7.0 cal.ka B. P.气候事件在中国多个地区都有明显的反映，整体表现为温度下降、夏季风强度减弱。与全球其他地区的古气候记录对比显示7.5~7.0 cal.ka B. P.气候事件可能具有全球性的特征。与驱动因子系列对比发现该气候事件发生在北半球夏季太阳辐射逐渐减少、太阳活动减弱、火山活动频发、劳伦泰德冰盖快速融化期间，表明这4种因素在7.5~7.0 cal.ka B. P.气候事件发生过程中发挥了作用。未来需要更多测年准确、分辨率高的古气候记录定量-半定量刻画该气候事件的变化幅度、起止时间以及区域差异，同时结合古气候模拟揭示7.5~7.0 cal.ka B. P.气候事件产生的动力机制。
Ocean drilling in the Bengal Fan has revealed the uplift history of the Himalayas and Indian mons... more Ocean drilling in the Bengal Fan has revealed the uplift history of the Himalayas and Indian monsoon,but there is no analogous deep-water fan in the Western Pacific marginal seas that can be drilled and used to constrain the Tibet uplift history from its eastern side.The Yangtze river,originating from northeastern Tibet and draining a large area prevailed by monsoon precipitation,is highly sensitive to plateau uplift and monsoon evolution.A systematical study of the Yangtze river deposits will test various hypotheses concerning plateau uplift and its link with monsoon evolution.Along the modern Yangtze river,the upper reach is decoupled from the lower reach by the Three Gorges.About 30% of the total sediment load from the Yangtze river is laid in the Jianghan Basin immediately out from the Gorges,~40% is deposited in the lower reach and delta,and only ~30% is transported to the East China Sea.Therefore,a combination of ocean and continental drilling along the Yangtze River will reco...
OSL dating of fine-grained quartz from Holocene Yangtze delta sediments Holocene flood events in ... more OSL dating of fine-grained quartz from Holocene Yangtze delta sediments Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail. In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4-11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by crosschecking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR 50 and pIRIR 160) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR 160 dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of 3 Gy ka-1). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ~6 ka between 9.65 and 5.50 m in core H1 and ~2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR 160 signals suggest less light exposure of the core top sediments and of those from the transition layer between ~6 ka to ~2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.
Hydroclimate variations associated with the East Asian Summer Monsoon (EASM) precipitation exert ... more Hydroclimate variations associated with the East Asian Summer Monsoon (EASM) precipitation exert significant impacts on lives of people inhabiting within the Yangtze River drainage and the coastal zone of South China. Seasonal shift of main precipitation area is attributable to the reposition of northern limit of summer monsoon, which would lead to provenance and composition changes of suspended materials transported by the Yangtze River. Consequently, the interannualto millennial -scale variability in the position of rain belt mentioned above could be recorded in the long-term change in compositional variation of the sediment originated from the suspended materials from the Yangtze River. The inner shelf sediments of the East China Sea (ECS) is of primary importance to study provenance changes of terrestrial materials from the Yangtze River. Because of this expectation, we examined provenance changes in MD06-3040 core sediments recovered from the inner shelf of ECS in association w...
A palaeomagnetic investigation of a late Quaternary loess-palaeosol sequence in central China has... more A palaeomagnetic investigation of a late Quaternary loess-palaeosol sequence in central China has revealed two episodes of anomalous geomagnetic field behaviour in the lower and upper parts of soil complex S1, which spans the last interglacial interval. Comparison of the ...
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