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Research in Geophysics

1.Geological Setting
     
Nepal, lies between India to the South and China to the North. It extends 800 km from East to West ranges and 130 to 230 km in North- South. The country is naturally separated into four major geographical/geological zones (Figure 15 and 16) parallel to its long dimension (Frank and Fuchs, 1970; Mitchell, 1979; Stocklin, 1980; Windley, 1983).

Terai
The Terai is the Nepalese portion of the Indo-Gangetic Plain that extends from the Indian Shield in the South to the Siwalik Fold Belt to the North. The plain is a few hundred metres above sea level and usually 400 to 600 m thick. it is composed of Recent of Quaternary alluvium, boulder, gravel, silt and clay. Terai Plain is underlain by a thick, relatively flat-lying sequence of Mid to Late Tertiary molasse (Siwalik Group) which uncomformably overlies subbasins of early Tertiary to Proterozoic sediments (Surkhet, Gondwana and Vindhyan Groups) and igeneous and metamorphic rocks of the Indian Shield (Agrawal, 1977; Acharya and Ray, 1982; Raiverman et.a.l, 1983).

Siwalik Fold Belt
The Siwalik Fold Belt is from 5 to 45 km wide and rises abruptly from the Terai along the Main Frontal Thrust (MFT). It consists of a series of ridges and valleys composed of thick beds of folded and faulted Tertiary Molasse of Siwalik Group thrust to the South (Parkash et.al., 1980; Herail et. al, 1986). Gravity measurements and detailed field mapping indicate that the cores of at least some of these structures contain pre-Siwalik rocks that are considered to be hydrocarbon objectives (Friedenreich and Slind, 1986; Elber, 1989).

Lesser Himalaya
The Lesser Himalaya is a wide, stratigraphically and structurally complex zone that lies immediately north of the Siwalik Fold Belt and is separated from it by the south-verging main boundary fault (MBT). The majority of the Lesser Himal is composed of thrust sheets and nappes of metasediments and metamorphic rocks with granitic intrusions of the Midland Group. The Group is of little hydrocarbon exploration interest, although the oil gas seeps of the Dailekh (Figure 9) area occur within the Midland Group (CPIT, 1973). These seeps are interpreted to have been generated in sediments below the nappes.

Higher Himalaya
The Higher Himalaya which contains the spectacular peaks of the Great Himalayan Range, Everest, Annapurna, etc. is thrust southward over the Lesseer Himalaya along the Main Central Thrust (MCT). The zone is composed of a basal slab of metamorphic Proterozoic rocks overlain by a conformable sequence of Cambrain to Eovene Tethuyan Sediments (Bordet et al., 1981). Gas seeps occur in the upper Tethyan of northen Nepal near the village of Muktinath (Figure 16).

     
2.Petroleum Exploration in Nepal
     
There are four major groups of rock units interesting for petroleum exploration in Nepal. These are the Siwalik, Surkher, Gondwana and Lakharpata (Vindhyan) Groups (Figure 15 and 16).

 

 

1.Geological Setting
     
Nepal, lies between India to the South and China to the North. It extends 800 km from East to West ranges and 130 to 230 km in North- South. The country is naturally separated into four major geographical/geological zones (Figure 15 and 16) parallel to its long dimension (Frank and Fuchs, 1970; Mitchell, 1979; Stocklin, 1980; Windley, 1983).

Terai
The Terai is the Nepalese portion of the Indo-Gangetic Plain that extends from the Indian Shield in the South to the Siwalik Fold Belt to the North. The plain is a few hundred metres above sea level and usually 400 to 600 m thick. it is composed of Recent of Quaternary alluvium, boulder, gravel, silt and clay. Terai Plain is underlain by a thick, relatively flat-lying sequence of Mid to Late Tertiary molasse (Siwalik Group) which uncomformably overlies subbasins of early Tertiary to Proterozoic sediments (Surkhet, Gondwana and Vindhyan Groups) and igeneous and metamorphic rocks of the Indian Shield (Agrawal, 1977; Acharya and Ray, 1982; Raiverman et.a.l, 1983).

Siwalik Fold Belt
The Siwalik Fold Belt is from 5 to 45 km wide and rises abruptly from the Terai along the Main Frontal Thrust (MFT). It consists of a series of ridges and valleys composed of thick beds of folded and faulted Tertiary Molasse of Siwalik Group thrust to the South (Parkash et.al., 1980; Herail et. al, 1986). Gravity measurements and detailed field mapping indicate that the cores of at least some of these structures contain pre-Siwalik rocks that are considered to be hydrocarbon objectives (Friedenreich and Slind, 1986; Elber, 1989).

Lesser Himalaya
The Lesser Himalaya is a wide, stratigraphically and structurally complex zone that lies immediately north of the Siwalik Fold Belt and is separated from it by the south-verging main boundary fault (MBT). The majority of the Lesser Himal is composed of thrust sheets and nappes of metasediments and metamorphic rocks with granitic intrusions of the Midland Group. The Group is of little hydrocarbon exploration interest, although the oil gas seeps of the Dailekh (Figure 9) area occur within the Midland Group (CPIT, 1973). These seeps are interpreted to have been generated in sediments below the nappes.

Higher Himalaya
The Higher Himalaya which contains the spectacular peaks of the Great Himalayan Range, Everest, Annapurna, etc. is thrust southward over the Lesseer Himalaya along the Main Central Thrust (MCT). The zone is composed of a basal slab of metamorphic Proterozoic rocks overlain by a conformable sequence of Cambrain to Eovene Tethuyan Sediments (Bordet et al., 1981). Gas seeps occur in the upper Tethyan of northen Nepal near the village of Muktinath (Figure 16).

     
2.Petroleum Exploration in Nepal
     
There are four major groups of rock units interesting for petroleum exploration in Nepal. These are the Siwalik, Surkher, Gondwana and Lakharpata (Vindhyan) Groups (Figure 15 and 16).