GEOLOGY OF THE AREA AROUND UTTARKASHI, GARHWAL HIMALAYA (UTTAR PRADESH_)

Abstract

The area under investigation lies in Uttarkashi District of Uttar Pradesh. It consists of approximately 50 sq.km. of Lesser Himalayan Terrain between latitude 300 40' and 300 50' and longitude 78° 20' and 780 30' in the Survey of India toposheet Nos. 53 J/5 and 53 J/6. The Bhagirathi river, one of the two chief tributaries of the river Ganga in the Lesser Himalaya, flows almost north-south across the area. The town of Uttarkashi is the district headquarter and an important pilgrimage centre for Hindus. It is situated on its right bank of Bhagirathi River (Pig. No. 1). 1.1 Accessibility : The nearest railway station for the area is Rishikesh from where an all weather road runs right upto Gangotri. Uttarkashi is 165 Km from Rishikesh by road. The road traffic is often dislocated on account of nume-rous landslides, particularly during the rainy season, i.e. between middle of June to end of August. Ordinarily, the traffic is confined during day time only. 1.2 Climate : The climatic condition in the Lesser Himalaya is 2 an important governing factor in carrying out field work. The diverse type of climates limit the field season only to a few months in summer. During this season the valleys are hot and humid. The rainy season assumes the ferocity during 3rd week of June and continues till August. The winter season is very cold particularly from December to March, while light rains are common at only higher altitude, the heavy downpour is confined in the valleys during the winter. The temperature varies from - 30 C to 300 C. The maximum annual rainfall is about 250 cm. 1.3 Phyeiography and Drainage As in any part of the Lesser Himalaya, the topo-graphy is typically immature, rugged, hazardous with thickly forested slopes. The area is characterised by N.N.W. - S.S.E. and W.N.W. - E.S.E. trending predominant ridges. In the western part, some of the ridges trend more towards N-S and NW-SE. On the left bank of the Bhagirathi river, the major ridges are the result of dissection by Dhanari and Gamrigad streams. . The elevation of the area varies from about 920 mts in the Bhagirathi valley near Dvnda to 2701 mts hill feature on Nagni Thank. The topographical map of the area shows many peaks which are more than 2500 mts in height. The area is drained by the mighty, turbulent perennial Bhagirathi, tributary of the river Ganga. The Bhagirathi drainage system includes the following important streams. (i) Dhanari Gad flowing in a general north westerly direction. (ii) Rano Gad, Sialam Gad and Kaldi Gad flowing towards south and draining a part of northern region near Uttarkashi, (iii) Baragadi Gad f~.ows in a north westerly direction, South of Uttarkashi. In the north, the Bhagirathi river flows almost east to west between Uttarkashi and Nakuri for about 10 Kms. At Nakuri, the river takes a sharp turn and changes its course in a N 100 E - S 100 E direction for about 20 Km upto Dharasu. The east-west trend of the river between Uttarkashi and Nakuri is peculiar to the area as it is characterised by broad 'U' shaped valley in comparison to typical 'V' shaped valley elsewhere. Jain (1971) attributes a part of the east-west segment of the river to correspond to a thrust delineated by him..........