Evolution of himalaya

evolution of himalaya and its whole description

1. ORIGIN AND TECTONIC EVOLUTION OF HIMALAYA Presented by under the guidance Sachin chandra Prof. a. k. shandilya M tech 1 st sem. sl. no. 19 Reg. no. y18251022

2. INTRODUCTION Himalaya made up of Sanskrit word Him+Alya means abode of snow. Youngest and highest mountain ranges on the globe. With many peaks as high as 7000m and highest peak is Mount Everest(8848)m Located on Southern fringe of Tibetan plateau and form a mountain arc convex towards the south about 2400km in length and 250 to 300km in width. The Himalaya are bounded by two structural bends (Nanga parbat, the I ndus gorge) and in Northeast (The Tsangpo gorge). Several large river like Ganges, Sutlej, Chenab, Brahmaputra, Jhelum etc. are arises in highlands of Himalaya and provide fresh water nearly 3 billion people in Asia. Sediments shed from the Himalaya have also formed extensive agricultural plains in Northern India, Pakistan and Nepal. Himalaya also act as topographic barrier to the summer-time warm monsoon wind comes from indian ocean and in the winter-time cold wind coming from Siberia and have caused cold and dry climate in Tibet but torrential rainfall on the valley and plains

3. Origin of Himalaya I ndia, Gondwana and Tethys About 500 mya a super continent comprised by Australia, India, Africa was assemble in Southern hemisphere geologist called Gondwana after the Gond Tribe in Central India where the first their sediment are studied. Within Gondwana India was adjacent to Madagascar-Africa on West and Antarctica on East. The paleotethys ocean bordered the Northern margin of Gondwana during Permian 275-260 ma. A series of continental fragments consisting turkey, Iran and Tibet drifted away from Gondwana thus opening of NeoTethys ocean on their trails. when continent spilt a part a large volcanic eruption affect some part of it. The Permian P anjal trap (Basalt) exposed in Pir panjal range of Kashmir are belief to be formed by continental rifting between Indian and Tibetan block.

4. Gondwana largely remained intact until the late Jurassic. In late Jurassic it started to fragment and created present day continent and ocean. Indian plate together with Madagascar drifted away from Africa in late Jurassic about 165 ma. Then indian plate separated from East to Antarctica about 135 Ma. then indian plate started Northward its journey across Neotethys ocean at same time indian ocean opening behind India. at the time of Cretaceous indian plate was passing over reunion hotspot which develop Deccan trap this also caused by Seychelles-Mauritius fragments separates from india . as india drifted Northward the Neotethys ocean floor began subducted these subduction occur beneath the southern margin of Asia along Karakoram and Tibet. this usually happen because oceanic crust mainly basalt is heavier than continental crust mainly granite. The subducted slab partially melts and produced large amount of granitic and volcanic rock in form of island arc. in North-West part of Himalaya(cretaceous age) KOHISTAN-LADAKH ISLAND ARC are present made up of volcanic rock which is simillar to northern PACIFIC OCEAN ABOUT 85 mya Kohistan – ladakh island arc collide with karakoram then oceanic floor is closed

5. India A sia collision Early-middle Eocene period During cretaceous and Paleocene india move northward at the rate of 15-20cm per year But slow down only about 5cm per year in 45 MYA these data come from examination of magnetic anomaly of rock on indian ocean floor from paleomagnetic analysis. Youngest granite in Trans-Himalaya produced by the subduction of Neotethys ocean beneath Asia are dated by radiometric dating is about 40 mya which indicate the ending of subduction. sedimentary record of Himalaya shows after lower – middle Eocene (55-44) the deposition change marine to continental

6. THE TECTONIC EVOLUTION OF HIMALAYA Himalaya is the product of 55 Ma of tectonic compression and structural deformation. Examination of geochronological structural petrological and sedimentary data suggested that there are 5 major in geological history of these mountain however the Himalaya drama began after the collision

7. DIAGRAMMATIC CROSS SECTION OF HIMALAYA

8. TRANS -HIMALAYA [AGE 55to30mya] . upper cretaceous vocanic and granitic rock , calc alkaline granite ,alkaline granite ITSZ [AGE 55 mya ] Theolitic volcanic rocks ,high pressure metamorphic rock {Green schist } Tethyan Himalaya [AGE 45 to 35 mya ] granite and gneiss, white leucogranite Silurian age { muth quartzite }, ophiolite melanges, nilgiri lime stone , kamdehan shale, cretaceous age flysh sand stone The higher Himalaya [AGE 24to17 mya ] central crystalline zone ,Proterozoic to Cambrian age igneous and metamorphic rock,white leucogranite of Miocene age. Lesser or lower Himalaya [AGE 11to7 mya ] metamorphosed sedimentary rocks – quartzite,marble,slate,phyllite,schist,gneiss , volcanic and granitic rocks of Proterozoic to Cambrian {2000-500} and low temperature metamorphic rocks Sub Himalaya or siwalik [AGE 2.6 to recent] Sand stone ,mud stone of Miocene ,Upper tertiary –marine lime stone of nari formation ,yellow lime stone of gaj formation ,grey sand stone of manchar formation INDO GANGETIC PLAIN

9. Sub Himalaya or siwalik [AGE 2.6 to recent] Sand stone ,mud stone of Miocene ,Upper tertiary –marine lime stone of nari formation ,yellow lime stone of gaj formation ,grey sand stone of manchar formation Lesser or lower Himalaya [AGE 11 to 7 mya ] metamorphosed sedimentary rocks – quartzite,marble,slate,phyllite,schist,gneiss , volcanic and granitic rocks of Proterozoic to Cambrian {2000-500} and low temperature metamorphic rocks The higher Himalaya [AGE 24 to 17 mya ] central crystalline zone ,Proterozoic to Cambrian age igneous and metamorphic rock,white leucogranite of Miocene age. Tethyan Himalaya [AGE 45 to 35 mya ] granite and gneiss, white leucogranite Silurian age { muth quartzite }, ophiolite melanges, nilgiri lime stone , kamdehan shale, cretaceous age flysh sand stone ITSZ [AGE 55 mya ] Theolitic volcanic rocks ,high pressure metamorphic rock {Green schist } TRANS -HIMALAYA [AGE 55to30mya] upper cretaceous vocanic and granitic rock , calc alkaline granite ,alkaline granite INDO GANGETIC PLAIN

10. Phase 1. The Trans-Himalayan Uplift (55 to 35 Ma Eocene) The first mountain range in Trans- H imalaya igneous arc. The granite rock of Trans-Himalaya indicate they are rapidly cooled and eroded at about 40 ma. Basin Southern front of the Trans-Himalaya filled with continental sediment which are Kargil , Kailash and lahasa

11. Phase 2. The Eo Himalayan phase : the tethyan Himalayan After the uplift of Trans-Himalaya tectonic deformation also affected T ethyan Himalaya. The sediment of Tethyan Himalaya escaped from metamorphism. There are still sedimentary rock and highly folded and faulted In Tethyan Himalaya ophiolite mélanges are formed by result of abduction of oceanic plate. In the Tethyan Himalaya PCM deposits (Passive continental margin) are present ( muth quartzite, niligiri limestone and kamdehan shale) which are marine in origin In Tethyan Himalaya flysh sandstone are present which indicate when subduction is started. Tethyan Himalaya separated from Greater Himalaya by South Tibet detachment (STD)

12. Phase 3. The Neo Himalayan Phase : The Higher Himalaya Uplift During early Miocene(24-17 ma) the higher Himalaya rock buried under 20 to 25 km deep They are metamorphosed and partially melted under temperature of 600-800 degree celcius rapid upliftment are seen along MCT (Main Central Thrust) with activity this fault the tethyan Himalayan zone was detached from higher Himalaya along normal fault called STD (South Tibet Detachment) In this region white leucogranite which are formed during 24-17 Mya rapidly uplifted along STD These granite constitute the core or the summit of the highest peak in the Himalaya including Manaslu and Annapurna in Nepal and Badrinath in kumoun Along the MCT we don’t find any Miocene age granite The slip of MCT is more than 150km MCT transported higher H imalaya metamorphic rock on to the Lesser Himalaya where find them as klippe and outlier

13. Phase 4. The Lesser Himalayan Uplift (11-7 mya ) During the late Miocene sedimentation rate in Siwalik Basin drastically increase Mineral kyanite which only formed in higher Himalayan metamorphosed rock to the North of MCT first appear in Siwalik sediment Structurally its shows simple anticline, syncline and synclinal fault showing jura type fault decollement The Southern boundary of Lower Himalaya is MBF (Main Boundary Fault) while the Northern boundary is MCT (Main Central Thurst ) which separates the Lower Himalaya to Greater Himalaya the uplift of Siwalik range along the Himalayan Frontal rock in 1.3 mya which indicates Neotectonics

14. The Himalaya’s Adventure Continues Geophysical surveys by the seismic (sound wave) reflection and gravity methods indicate that the crustal thickness beneath the Himalaya is about 70 km, which is twice that of a normal continental crust (for example, the Indian Peninsula). In other words, the Himalaya are higher because these mountains are sitting on an over-thickened continental crust, produced by compression, thrusting, and folding . Geologists believe that all major faults in the Himalaya, including the Normal Himalayan Thrust, the South Tibetan Detachment, the Main Central Thrust, the Main Boundary Thrust, and the Himalayan Frontal Fault, are all joined at depth to a major shallow-dipping structure, called the Main Himalayan Thrust or Decollement (a French word meaning Detachment ). This structural model together with the available geologic data discussed in this article implies that as the Indian plate has pushed northward, thrust faults have developed sequentially from north to south and that as a new thrust fault has ruptured, the tectonic push has added some elevation to the entire Himalaya. In other words, the present elevation of the Himalaya is a cumulative effect of 55 million years of continental collision, a magnificent drama of episodes which geologists have painstakingly pieced together and are beginning to make sense of it . A period of 55 million years or so since the India-Asia collision may seem a long time from human perspective, but by Earth’s standards , the Himalaya are still young, rising mountains.