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Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai.

Xu H, Liu B, Wu F - Geochem. Trans. (2010)

Bottom Line: Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship.The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales.Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710075, China. xuhai@ieecas.cn.

ABSTRACT
The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However, the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment.

No MeSH data available.


Spatial patterns of mass accumulation rates and magnetic susceptibility (a), SiO2 (b) and Ti (c) contents, and Rb/Sr ratios (d) of the surface sediments in Lake Qinghai. The horizontal coordinates are arranged according to both mass accumulation rate and the distance from sampling sites to the estuaries and/or lake shoreline. The magnetic susceptibility is highly positively correlated with the corresponding Fe contents (r = 0.9; figure not shown). Elements of the mixed-cores and those of the 1963-sect for each site have similar spatial patterns.
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Figure 3: Spatial patterns of mass accumulation rates and magnetic susceptibility (a), SiO2 (b) and Ti (c) contents, and Rb/Sr ratios (d) of the surface sediments in Lake Qinghai. The horizontal coordinates are arranged according to both mass accumulation rate and the distance from sampling sites to the estuaries and/or lake shoreline. The magnetic susceptibility is highly positively correlated with the corresponding Fe contents (r = 0.9; figure not shown). Elements of the mixed-cores and those of the 1963-sect for each site have similar spatial patterns.

Mentions: As shown in Fig. 3, the spatial patterns of mass accumulation rate, magnetic susceptibility, major elements, and Rb/Sr ratios are similar. Our most recent work revealed that SiO2, Ti, Fe, Al2O3 are the main components of lake sediments [7]. These elements have higher contents near bank/estuary areas, while lower at the central region. Therefore, mass accumulation rates of surface sediments are mainly dominated by accumulation of terrigenous detritus (Fig. 3; refer to [7] for more details). On the contrary, the chemically/biogenically deposited components have lower contents near bank/estuary areas but higher at central lake. These suggest that the spatial pattern of Rb/Sr ratios are dominated by input of terrigenous detritus.


Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai.

Xu H, Liu B, Wu F - Geochem. Trans. (2010)

Spatial patterns of mass accumulation rates and magnetic susceptibility (a), SiO2 (b) and Ti (c) contents, and Rb/Sr ratios (d) of the surface sediments in Lake Qinghai. The horizontal coordinates are arranged according to both mass accumulation rate and the distance from sampling sites to the estuaries and/or lake shoreline. The magnetic susceptibility is highly positively correlated with the corresponding Fe contents (r = 0.9; figure not shown). Elements of the mixed-cores and those of the 1963-sect for each site have similar spatial patterns.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2909147&req=5

Figure 3: Spatial patterns of mass accumulation rates and magnetic susceptibility (a), SiO2 (b) and Ti (c) contents, and Rb/Sr ratios (d) of the surface sediments in Lake Qinghai. The horizontal coordinates are arranged according to both mass accumulation rate and the distance from sampling sites to the estuaries and/or lake shoreline. The magnetic susceptibility is highly positively correlated with the corresponding Fe contents (r = 0.9; figure not shown). Elements of the mixed-cores and those of the 1963-sect for each site have similar spatial patterns.
Mentions: As shown in Fig. 3, the spatial patterns of mass accumulation rate, magnetic susceptibility, major elements, and Rb/Sr ratios are similar. Our most recent work revealed that SiO2, Ti, Fe, Al2O3 are the main components of lake sediments [7]. These elements have higher contents near bank/estuary areas, while lower at the central region. Therefore, mass accumulation rates of surface sediments are mainly dominated by accumulation of terrigenous detritus (Fig. 3; refer to [7] for more details). On the contrary, the chemically/biogenically deposited components have lower contents near bank/estuary areas but higher at central lake. These suggest that the spatial pattern of Rb/Sr ratios are dominated by input of terrigenous detritus.

Bottom Line: Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship.The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales.Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710075, China. xuhai@ieecas.cn.

ABSTRACT
The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However, the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment.

No MeSH data available.