The Himalaya was formed due to collision of Indian Plate and Eurasian Plate at about 40 million years ago. It extends in 2400km east - west direction. Its width varies from 230 to 320 km and bounded between the Indo-Gangetic Plain in the south and Tibetan Plateau in the north. Nepal Himalaya occupies the central 800km part.
Heim & Gansser 1939, and Gansser 1964 divided the rocks of the Himalaya into four tectonostratigraphic zones that are characterised by distinctive stratigraphy and physiography. From south to north, it can be divided into five latitudinal morpho-tectonic zones and these are :
1. The Gangatic Plain (Terai)
2. The Sub Himalayan (Chure or Siwalik)
3 Lesser Himalayan (Mahabharat Mountain Range),
4. Greater Himalayan, and
5. Tibetan Himalayan zones (Tethys Himalaya).
Each of these zones is clearly identified by their morphological, geological and tectonic features. Main Frontal Thrust (MFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT) and South Tibetan Detachment Fault system (STDFS), from south to the north respectively are the major linear geological structures that act as the boundary line between the two consecutive units . From mineral resources point of view, Terai Plain is potential for gravel, sand, ground water and petroleum. The Sub Himalaya is the potential area for construction materials, petroleum and natural gas. Similarly, Lesser Himalaya is promising for metallic minerals, industrial minerals, marble, gemstones, fuel minerals, construction materials etc. Some of the areas in Higher Himalaya are highly promising for precious and semiprecious stones, marble and metallic minerals. Tibetan Tethys zone is prospective for limestone, gypsum, brine water (salt) and natural gas.
DMG has published regional Province wise geological Maps of Nepal.
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