Geotraverses through Higher and Tethyan zones of Lahaul and Spiti sector of N-W Himachal and adjoining part of Ladakh Himalaya

Abstract

Systematic geological cross-sections along traverses of Manali-Leh Highway, Satluj River section, Spiti River section and Pin and Parahio River sections have been sketched in course of expeditional work. An attempt has been made to illustrate the real ground picture visible in the field, keeping as far as possible in mind the vertical and horizontal scales and directional orientation. The extrapolation has been avoided. The profile along the Manali-Leh Highway presents the picture of tectonic contact between central crystalline unit of Vaikrita and thick sedimentary sequence of Phanerozoic with Haimanta Group at the base. Unique features of inverted Mesozoic synform and younger granitic intrusion along the deep fracture have been illustrated. Along the profile of Satluj Valley the Rampur antiform with Precambrian volcanics is succeeded by Vaikrita crystalline of high grade metamorphism ending up with tectonic contact with Tethyan sediments at Khab, sense of movement and intrusive granitic rock-types suggest the nature of visible thrust contact. The profiles along Spiti, Pin and Parahio rivers are very illustrative to confirm the missing carboniferous zone - the conjectural flexure of Hercynian orogenic phase. Profuse disharmonic folding with Triassic horizon and thrust structures with limited displacements within the formations have also been noticed. Structural profiles indubitably confirm the tectonic contacts on either side of the Tethyan sedimentary sequence. Low amplitude thrusting and recumbent folds are sometimes indicative of vivid tectonic phenomenon within the thick pile of deformed Tethyan sequence.