Sliding of an old toppled block in the Chor Khola area, Siwalik Hills, Mid-Western Nepal

Abstract

An old toppled block was recognised near the confluence of the Surai Khola and Chor Khola in the Siwaliks of Mid-Western Nepal. The block occupies an area of about 17,000 m² and is represented by an interbedded sequence of sandstone and mudstone of late Miocene age. Most of the strata dip northwards, but some of them dip southwards as well. The strikes of the right-side- up and overturned strata are almost uniform, and the axis of toppling is essentially horizontal. The direction of toppling is N12° W with the rotation angle ranging between 74° and 118°. The toppling and sliding are closely related to rapid incision of the Surai Khola and the Chor Khola, and tilting of the strata due to faulting. The toppling may be as old as late Pleistocene, whereas the sliding is a recent phenomenon.