| During recent years,evolution history and deposition development of large-scale river systems,especially originated from the inland mountains and poured into the marginal seas,have been paid more and more attention.The Yangtze River,as the most important linkage between the Tibet Plateau and East Asian marginal seas,delivers great volume of water,sediment and relevant chemicals from its headwater regions and tributaries to the East China Sea,significantly affecting regional geochemical cycles,environment evolution,and depo-systems development in these areas.Thus,investigation of the source to sink transport pattern of the Yangtze River materials allow us to better understand these phenomena.In the past few decades,variously source tracing methods have been performed on the modern Yangtze River sediment and geo-historical deposit.However,diverse source tracing methods resulted in diverging consequences,the unified cognition remains confusion,which generally owing to the limitation of the source tracing method.Thus,more new source tracing methods should be applied to provide more significance recognition.Based on “source to sink” process of the Yangtze River,in this study,the Electron Spin Resonance(ESR)signal intensity and crystallinity index(CI)were firstly applied to tracing sediments provenance.Firstly,we investigate characteristics of quartz ESR signals intensity and crystallinity index derived from granitic,metamorphic and sedimentary bedrocks in small river systems.Secondly,the potential use of ESR provenance tracing method was examined in modern Yangtze River sediments,including mainstream and major tributaries.In addition,the grain size characteristics and resetting features of multiple quartz ESR signals of the Yangtze materials were also verified to provide basic information for the later experiment.The main conclusions of this paper are listed as below:1.Grain size analysis result show that the priority size fraction of surface Yangtze River is 125 ~ 500 ?m,occupied 80 % of the whole particles.Then is the finer fraction(< 125 ?m)and courser fraction(> 500 ?m),which both occupied about 10 % of the whole particles.The particles in mainstream show a fining trend of sediment grain size from source to sink.2.Artificial sunlight bleaching experiment show that the Al center signal will be reach the steady residual status after 300 h while the Ti center of four options are absolutely bleached to zero after about 250 h.The E'center will be enhanced in firstly 16 h,and reach the maximum value between 32 and 230 h,then decreased.But,we newly find that after 400 h,the E'center signal intensity reach a stable increase level,about 2.5 times of its nature.3.The hearting experiment show that the E'center will also increase before 300 ?,and then decrease until disappear after 500 ?.The heat-treated E'center will be reach the maximum signal intensity at about 300 ?.We also notice that the heat-treated E'center various sample will be reach the maximum signal intensity at different heating temperature,which around at 300 ?.4.Heating effect on fluvial granitic quartz extracted from various formation age bedrocks show that the quartz heat-treated E'center will be proportional to the age of quartz with higher value for quartz from older mother rocks.Regression equation simulation was made to better understand correlation between quartz formation age and its heat-treated E'center intensity heated at different temperature,the result indicate that the regression coefficient at 300 ?(0.93)is higher than that(0.84)of 330 ?,imply that the heat treated E'center of fluvial sediment quartz would also reach the maximum value at 300 ?.5.Nature E'center signal intensity analysis of quartz extracted from granitic,metamorphic and sedimentary bedrocks and sediments in small river systems show that the nature E'center intensity varied obviously among the three bedrock types.The nature E'center signal intensity can directly reflect the mother-rock types,such as the value of metamorphic and sedimentary quartz is much larger than that of granitic quartz.The nature E'center intensity will be enhanced by sunlight from source to sink.6.Nature E'center intensity,heat-treated E'center intensity,the ratio between Al center and Ti center and the CI of quartz extracted mainstream and major tributaries varied significantly among the Yangtze River Basin.The each indicator value of upper reaches is always higher than that of middle-lower reaches.The nature E'center intensity and the ratio between Al center and Ti center can reflect the bedrock type of each Yangtze River tributary while the heat-treated E'center intensity is closed to the bedrock age among each branch drainage.Combination of heat-treated E'center and CI value can be used as an effective sediment tracer applied in the Yangtze River Basin.Moreover,combination of heat-treated E'center and nature E'center also show a good spatial distribution among the Yangtze River Basin,this would be an potential source indicator in river systems.7.Based on the quantitative analysis of the ESR signal intensity,the generally result show that the sediment of the mainstream mainly sourced from the upper reaches and Han Jiang.Contribution of sediments from tributaries,including Gan Jiang,Xiang Jiang,Zi Shui,Yuan Jiang,Li Shui,and upper Jinsha Jiang are less.In upper reaches,Yalong Jiang and Jialing Jiang as well as the mainstream from Pan Zhihua to Nan Xi are major sediment sources.Compared with previous study,the contribution of Min Jiang and Da Duhe is deducting,we propose that the lots of dam built in Da Duhe river after 2013 maybe cause the situation.8.Based on the provenance interpretation of quartz heat treated E'center and CI,we propose that the YGL represents the sediment source derived from the upper Yangtze River Basin above the Three Gorges Valley.Combined with ESR chronology of YGL,we conclude that the Three Gorges Valley was channelized no later than 1.12 Ma ago.In general,on the one hand,nature E'center ESR signal intensity and ratio between Al center and Ti center can reflect bedrock types;on the other hand,the heat-treated E'center intensity refer to the bedrock ages.Both of the two characteristics make the ESR signals can be used as effective fluvial sediment source tracing indicators.In addition,with the development of ESR dating and improvement of ESR measurement technique,the ESR source tracing method show a potential use in the application of geo-historical deposit section.However,as a newly established source tracing method,the ESR source tracing method need more basic experiments and applications to better understand the relationship between sediments and its bedrocks before establish a well developed ESR source tracing method. |
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