238U–234U–230Th disequilibria and timescale of sedimentary transfers in rivers: Clues from the Gangetic plain rivers

Conceptual assessment of (dis)connectivity and its application to the Ganga River dispersal system

“…As noted earlier, the data on sediment flux (Galy et al, 1999;Metivier and Gaudemer, 1999;Goodbred, 2003;Chabaux et al, 2006) show that these are not coherent. If higher sediment residence time of 250 ka to 2 million years is considered after Metivier and Gaudemer (1999) and Chabaux et al (2006), the B type connectivity class for the Ganga River basin is indicated through trajectory 1.…”

“…As noted earlier, the data on sediment flux (Galy et al, 1999;Metivier and Gaudemer, 1999;Goodbred, 2003;Chabaux et al, 2006) show that these are not coherent. If higher sediment residence time of 250 ka to 2 million years is considered after Metivier and Gaudemer (1999) and Chabaux et al (2006), the B type connectivity class for the Ganga River basin is indicated through trajectory 1. However, if the millennial-scale transfer of signals of processes between the Himalaya and delta sedimentation are considered as suggested by Galy et al (1999) and Goodbred (2003), class C connectivity through trajectory 2 would be favored.…”

“…The value of residence time in the diffusion model was based on the elevation difference between upstream and downstream ends of the plain, channel length, floodplain width and sediment yield (Metivier and Gaudemer, 1999). Further, a recent study based on 238 U-234 U-230 Th disequilibria series computed the sediment residence time in transverse drainage systems from the mountain front to the confluence with the Ganga River as 150 ka for the mountain-fed Ghaghra River and 250 ka for the plains-fed Rapti River (Chabaux et al, 2006). This suggests that the average residence time in the EGP is in the range of 150-250 ka, with the implication that the Himalaya and the Bengal delta region cannot be considered as connected parts of the dispersal system within the time frame of 150 ka, i.e.…”

U-series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains: The case of the Himalayan rivers

“…This sediment residence time represents the time elapsed since production of solid erosion products from the bedrock, and integrates the storage time in weathering profiles and the transport time in the river (with possible temporary storage in a floodplain). The analysis of uranium-series (U-series) disequilibria in river dissolved and solid loads allows to perform weathering mass balance calculations at the scale of the watersheds and has been used to quantify the sediment residence time in various catchments around the world (e.g., Vigier et al, 2001Vigier et al, , 2005Chabaux et al, 2003aChabaux et al, , 2006Chabaux et al, , 2008Dosseto et al, 2006aDosseto et al, ,b,c, 2008aGranet et al, 2007). These studies, especially when comparing the results of the Amazon river system (Dosseto et al, 2006a,b) with those of the Ganges (Chabaux et al, 2006;Granet et al, 2007), give however quite different time-scales for sedimentary transfer in the alluvial plains: about 20 kyr with the Amazon river and 100 kyr or more for the Ganges.…”

Correlations of natural radionuclides in sediment from Danube

“…The transport and mobility of radionuclides in the aqueous system is another important factor influencing the content of radionuclides in river sediment at a given place. In view of these facts, radionuclides from the uranium and thorium series have been used for a long time as tracers and chronometers in studies of weathering (Porcelli et al, 2001;Dosseto et al, 2006a;Chabaux et al, 2006), as well as in studies of transport and the environmental behavior of natural radionuclides (Singh et al, 2003;Dosseto et al, 2006b).…”