evolution of siwalik.pptx
- 1. RISE OF HIMALAYAS AND EVOLUTION OF SIWALIK
- 2. Introduction • The most dramatic and visible creation of plate tectonics forces are the Himalayas, which stretch 2900 Km along the border between India and Tibet • Form between 40-50 mya • Collision of India and Eurasia
- 3. The INDIA –ASIA Collision • The world was a single landmass called Pangea • Pangea broke into two landmass. The northern landmass was Laurasia and the southern landmass was Gondwana Land. • comprised by Australia, Antarctica, India, Africa, and South Africa, • India was adjacent to Madagascar-Africa on the west • India was drifted away from Antarctica around 135 ma • began its northward journey across the Neo-Tethys Ocean, • Rise of himalaya has been related with the northward drift of Indian plate and its consequent collision with Asian plate • Northward drift of Indian plate began with the fragmentation of Gondwanaland and opening of proto- Indian ocean during the Jurassic period • Palaeomagnetic data of Indian ocean suggest that the northward drift of the Indian plate was most rapid during the paleocene epoch • This was also the time of extrusive volcanism (Deccan Trap) over the major part of the indian peninsula
- 4. • Collision of Indian plate with Asian plate-early eocene • Collision retard the pace of the northerly drift of the Indian plate • Drift was resumed at the beginning of oligocene with a slightly changed direction of translation • Indian plate began its rotational movement giving rise the formation of syntaxial bend at the north western extremity of the himalayan mountains
- 5. The six zones of Himalayas
- 6. (1) The Trans-himalaya • the Trans-Himalaya is made up of granitic and volcanic rocks formed from 110-40 million year ago (Ma). These igneous rocks intruded the metamorphic and sedimentary rocks of the southern Tibetan block. • The Trans-Himalaya is geographically divided into several areas: Kohistan , Ladakh , Kailash, Gangdese, Lhasa , and Mishimi
- 7. (2) The Indus-Tsangpo Suture Zone • A 'suture zone' is a tectonic line along which two continental plates collide and join each other • The Indus-Tsangpo Suture Zone marks the boundary between the Indian and Asian plates. • ocean- floor volcanic rocks, subduction-related high-pressure metamorphic rocks (greenschist rocks), and deep-sea sediments of the Tethys Ocean.
- 8. (3) The Tethyan (Tibetan) Himalaya • This zone consists of Cambrian through Eocene sediments (sandstone, shale and limestone) which were deposited on the continental shelf of the Tethys Ocean. These sedimentary rocks contain many kinds of fossils including the Cretaceous-age ammonite fossils • Tethyan sediments are exposed in Kashmir, Zanskar, Chamba, and Spiti. With a width of about 100 km, the Tethys Himalaya is the widest zone of the Himalaya. • the Tethys Himalaya is separated from the Higher Himalaya by a major normal fault called the South Tibetan Detachment
- 9. (4) The Higher (Greater) Himalaya • the backbone of the Himalayan mountains, is made up of 10-20 km- thick metamorphic rocks (schist and gneiss) and granites also find white granites (leucogranites) • the Higher Himalaya is thrust over the Lesser Himalaya along the Main Central Thrust
- 10. (5) The Lesser (Lower) Himalaya • south of the Higher Himalaya (the Main Central Thrust) lies the Lesser Himalaya which consists of metamorphosed sedimentary rocks (quartzite, marble, slate, phyllite, schist and gneiss • The stratigraphic thickness of the rock sequence in this zone is 10- 20 km. In a plate-tectonic setting, the Lesser Himalaya, like the Tethyan Himalaya and the Higher Himalaya, belongs to the northern margin of the Indian plate. • elevations of 2000-3000 m
- 11. (6) The Sub-Himalaya or the Siwalik Range • The Sub-Himalaya (or the Outer Himalaya) geographically corresponds to the Siwalik range foothills ranging in elevation from 250-800 m. • This zone is made up of 10-km thick succession of sandstone and mudstone shed from the Himalayan mountains, and carried and deposited by rivers, especially since the Miocene • These sediments have yielded abundant fossils of mammals
- 12. • Rise of himalaya was accomplished in series of five or more impulses punctuated by interval of comparative quiescence First movement (late cretaceous-early eocene) Dominated with emplacement of Dras volcanic in northern borders of mountains.extensive volcanism represents paleo- island arc system thatformed at the commencement of Himalayan orogeny Accompanied by intense deformation and regional metamorphism and emplacement of granitic gneiss in three deeper parts of the orogen Granitic gneisses represents remobilized precambrian basement of the basinTethys ses furrowed in to longitudinal ridges and basin as a consequent of the first tectonics movement of the himalayan orogeny
- 13. Second movement (late eocene) • Started when Thethyan Himalaya uplifted as a land mass • Accompanied by emplacement of tourmaline granites in the metamorphites and granitic gneisses that comprises of higher himalayan zone • Lesser Himalayan basin became shallower with the partial withdrawal of Marine water • Brackish water sediments were laid in these basins during late eocene-oligocene time
- 14. • Third movement (middle miocene) • Rocks of lesser Himalayan zone were deformed in to broad fold trending parallel to the Himalayan chain of mountains • Thrust sheets originating from the northern parts were piled one over the other in a southward translational movement • The nappens were further folded and thrust faulted due to continued south directed couple movement of the rising Himalaya • Tethys disappeared more or less and bring replaced by mountain ranges with intervening shallow lakes, marshes, and large river valleys • At the same time, long narrow throughs seems to have formed between rising Himalaya and peninsular masses
- 15. Fourth Upheaval (pliocene-pleistocene) • Resulted in the rise of Himalayan foothills • Rise of outer Himlaya coincide with the Pleistocene ice ages which led to the virtual extinction of the rich mammalian fauna of this age • This tectonic phase give rise to the formation of broad folds • The rocks of the foredeeps and a series of longitudinal thrust folds that seperates the lesser Himalayan zone from outer Himalayas.these are known as main boundary thrust
- 16. Fifth Upheaval (Early Pleistocene) • Pirpanjal was raised up to its present and possibly other ranges in lesser Himalayas • This is a kind of isotatic adjustment after the removal of ice sheet • Pirpanjal elevated to a height of several thousand feet in which that were originally deposited
- 17. The evolution of siwalik Sivaliks are the mountain range of outer Himalayas that stretches over about 2400 km from the Indus river eastwards close to Bhramaputra River The siwalik groups occur in potwar basin in NW Pakistan and extends along the Himalayan foothills to Arunanchal Pradesh. It extends in Pakistan, Jammu and Kashmir, Himachal pardesh, Uttaranchal and Nepal which is running parallel to the Himalayas.
- 18. • The region was a vast basin during middle miocene to upper Pleistocene times • The sediments were deposited by rivers flowing southwards from the greater Himalayas, resulting in extensive multiordered drainage system • Following the depositions the sediments were uplifted through intense tectonic regime's resulting in a unique topographic entity- SIWALIK HILLS
- 19. STRATIGRAPHY AND SEDIMENTATION • Siwalik group have been grouped into lower,middle and upper divisions based on lithostastigraphy. • Lower siwalik: Fine grained indurated sandstone, brightly coloured shales usually red, red nodular clays. • Middle siwalik:sandstone bodies with interbedded siltstone and shale, followed by mudstone, Marl and finally pebble sandstone and sandy conglomerate indicates of floodplain deposits. • Upper siwalik: Thick boulder conglomerate and grits, thick soft earthy clays except in the neighborhood of valleys emerging from middle Himalayas.
- 21. FAUNA FROM SIWALIK • The siwalik group is well known for their vertibrate fauna,
- 23. Conclusion • The Himalayan mountain is one of the youngest in the world And still rising mountain • The lithology and rock type is highly variable throughout and this variation suggests that a variety of processes were involved in the evolution such as subduction, thrusting, various phases of sedimentation • The himalayan contain the third largest deposit of ice and snow in the world, after Antarctica and the Arctic • The Himalayan range encompasses about 15000 glaciers which store about 12000 Km³ of fresh water