Geomorphic Implications of Late Pleistocene Surficial Sand Deposits in the Lower Khumbu Region, Nepal

In the Lower KhumbuLower Khumbu of eastern NepalEastern Nepal, several well-bedded, sandy/silty deposits are perched high on hillslopes with no obvious connection to a depositional setting. In this study we utilize infrared stimulated luminescence analysis (IRSL) to determine the age of deposition of six of these deposits as a first step in understanding the environment in which they formed. This area of the high HimalayaHigh Himalaya has experienced multiple glaciations as well as large and small landslide events. From field mapping and literature review we propose several possibilities for how these deposits fit into the regional Quaternary history. The data suggest that the strath terrace of PhortsePhortse was carved during a glacial advance around 42 ka. Towards the south, the KhumjungKhumjung Rockslide Complex occurred before 26 ka and was probably triggered by a paleo, mega-earthquake. Smaller landslide events cut the KhumjungKhumjung Rockslide to create the amphitheater that hosts the village of Namche BazarNamche Bazaar-Namche Bazar. These smaller events post-date 26 ka. This post-26 ka time also aligns with deposits near the ridge of the TyengbocheTyengboche monastery. Seismic events could have been responsible for triggering several events at 24–26 ka.