Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sedim...Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite （〉68%） is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea （SCS）. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe （Yellow） River. The relatively high abundant kaolinite is likely derived from the Changjiang （Yangtze） River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River＇s submerged delta have much lower 87Sr/S6Sr ratios （0.716 2-0.718 0） than those of the Shandong Peninsular mud wedge （0.721 6-0.724 9）, which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments, 展开更多
From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine se...From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine sediments can be used to shed light on the environment and climate change of the catchment. To provide such insight, we used the major element, trace element and rare earth element（REE） compositions in the southern Yellow Sea（SYS） sediments to reconstruct the changes in weathering and erosion of their source regions. The sediments originate predominantly from the upper crust of East China and are transported into the basin especially by the Yellow River（Huanghe） and to a lesser extent by the Yangtze River（Changjiang）. The chemical index of alteration（CIA; 53.7–59.7） suggests low chemical weathering of the source rocks since the Middle Holocene. This is consistent with the relatively cool and arid climate in North China after the Holocene Megathermal. Comparison of element ratios, including Al/Ca, K/Ca, Al/Na, K/Na, Rb/Sr, Li/Ba and the CIA shows that we can use the latter as a robust proxy for climate change. The CIA-based mean annual precipitation and mean annual temperature show a series of climate fluctuations in the catchment. A relatively warm and humid Period I（5.3–2.9 cal. ka BP）, a relatively cool and dry Period II（2.9–0.9 cal. ka BP） and an increasingly cool and dry Period III（0.9–0.3 cal. ka BP）. These periods can be linked to climate intervals recognized elsewhere.展开更多
Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.He...Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.展开更多
基金This work was supported by the research grant of the Cheju National University of Year 2006.
文摘Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite （〉68%） is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea （SCS）. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe （Yellow） River. The relatively high abundant kaolinite is likely derived from the Changjiang （Yangtze） River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River＇s submerged delta have much lower 87Sr/S6Sr ratios （0.716 2-0.718 0） than those of the Shandong Peninsular mud wedge （0.721 6-0.724 9）, which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments,
基金funded by the"Strategic Priority Research Program"of Chinese Academy of Sciences(Nos.XDA11020102 and XDA05030402)the National Natural Science Foundation of China(No.41376090)+2 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20120145120017)the Marine Safeguard Project(No.GZH201200503)the Special Fund for Basic Scientific Research of Central Colleges,China University of Geosciences Wuhan
文摘From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine sediments can be used to shed light on the environment and climate change of the catchment. To provide such insight, we used the major element, trace element and rare earth element（REE） compositions in the southern Yellow Sea（SYS） sediments to reconstruct the changes in weathering and erosion of their source regions. The sediments originate predominantly from the upper crust of East China and are transported into the basin especially by the Yellow River（Huanghe） and to a lesser extent by the Yangtze River（Changjiang）. The chemical index of alteration（CIA; 53.7–59.7） suggests low chemical weathering of the source rocks since the Middle Holocene. This is consistent with the relatively cool and arid climate in North China after the Holocene Megathermal. Comparison of element ratios, including Al/Ca, K/Ca, Al/Na, K/Na, Rb/Sr, Li/Ba and the CIA shows that we can use the latter as a robust proxy for climate change. The CIA-based mean annual precipitation and mean annual temperature show a series of climate fluctuations in the catchment. A relatively warm and humid Period I（5.3–2.9 cal. ka BP）, a relatively cool and dry Period II（2.9–0.9 cal. ka BP） and an increasingly cool and dry Period III（0.9–0.3 cal. ka BP）. These periods can be linked to climate intervals recognized elsewhere.
基金supported by the National Natural Science Foundation of China(Project No.41807448)。
文摘Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.
