Geological and Petrographical Investigations for the Mountain Hazards Mapping Project, Khumbu Himal, Nepal

Abstract

Geological and petrographical investigations of the Khumbu area, Nepal, were undertaken to provide basic data for the United Nations University mountain hazards mapping project. Six litho-tectonic units were distinguished by petrographical means: Basal Paragneisses, Migmatitic Orthogneisses, Upper Khumbu Gneiss Complex, Upper Paragneisses, Tertiary Leuco-granites, Everest Meta-Sediments. Investigations of subsurface conditions showed that the topographical relief of the area depends largely on lithology, structures, and the depositional or erosional character of the Late-Cenozoic glaciations. Mass wasting plays a major role in the accumu- lation of debris cover. The valley system has been interpreted as a deep pre-glacial primitive surface, with V-shaped troughs and elevated platforms, which have been overprinted by glaciation. Erosional activity of the river system is occurring at present although most of the landforms are relatively stable.