Geochemical analyses of sandstones and mudstones from the Siwalik succession, Surai Khola, western Nepal

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　This report contains whole-rock major and trace element XRF analyses of Middle Miocene to Pleistocene Siwalik Group sandstones (96) and mudstones (80) from the Surai Khola section of western Nepal. All were analyzed by X-ray fluorescence for the major elements and 14 trace elements. The data form part of a larger study of the geochemistry of the Siwalik Group, and supplement a similar data set from the Siwaliks in the Bakiya Khola section in central Nepal (Ulak et al., this volume). Analyses are reported for the Bankas (n=21), Chor Khola (n=62), Surai Khola (n=41), Dobata (n = 32) and Dhan Khola Formations (n=20), in ascending stratigraphic order. Normalization of average sandstone and mudstone from each formation against average upper continental crust (UCC) shows Na and Sr are strongly depleted relative to UCC, whereas several immobile elements (e.g. Zr, Th, Sc, Ti) are slightly enriched. However, fractionation between sandstone and mudstone within each formation is limited, particularly in the upper part of the section, and in comparison to the Bakiya Khola section in central Nepal. This suggests that some lateral geochemical variation exists within the Siwalik succession. This aspect will be the subject of future work.