Sr Isotopic Composition of Suspended Particulate Material (SPM) of East Siberian Rivers: Sediment Transport to the Arctic Ocean

Abstract

In order to determine the paths of sediment transport to the Laptev Sea and on to the Arctic Ocean we measured 87Sr/86Sr ratios and Sr concentrations of suspended particulate material (SPM) of the Lena, Yana, and Khatanga rivers. The SPM exported to the Laptev Sea by the Lena river is characterized by an average 87Sr/86Sr ratio of 0.7165 ? 0.0005 and a Sr concentration of 200 ? 20 ppm measured at the northernmost stations. The average 87Sr/86Sr ratio (0.7141 ? 0.0002) and Sr concentration (152 ? 5 ppm) of the Yana river SPM can clearly be distinguished from those of the Lena river SPM. Sr isotopic ratios (0.7102 ? 0.0002) and Sr concentrations (181 ? 5 ppm) of the Khatanga river SPM are strongly influenced by volcanic rocks of the Siberian Trap that are very common in the drainage area. Variations in Sr concentrations and isotopic ratios along the Yana and Khatanga rivers result from mixing of material supplied by individual tributaries. The Lena river SPM, on the other hand, exhibits variations which cannot be explained by simple mixing of tributary sediments. Various processes, such as dissolution/absorption and grain-size separation, are considered. The Sr isotopic ratio of each river SPM can be related to isotope data of Laptev Sea surface sediments and sediments incorporated into sea ice. Both indicate that the 87Sr/86Sr ratios can be applied to identify the distribution of riverine material in the Laptev Sea and the Arctic Ocean.