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Himalaya, the Northern Frontier of East Gondwanaland
Gondwcina Research, K I , No. I . pp. 3-9. 0 I997 International Association for Gondwnna Research. J a p n .
ISSN: 1342-937X
Himalaya, the Northern Frontier of East Gondwanaland K.S. Valdiya Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore - 560 064, India (Manuscript received January 9, 1997; accepted January 30,1997)
Abstract The Himalayan province, which represents the northern platform of the Peninsular India belonging to East Gondwanaland, was strongly affected by PanAfrican diastrophism 500f25 Ma ago. This brought to an end the protracted Purana cycle of sedimentation throughout the Peninsular India and the Lesser Himalaya and interrupted basin-filling in its northern Tethyan domain. But the sea returned in the Early Permian along a narrow depression formed due to rifting of the Himalayan crust in what is today the southern Lesser Himalaya. In the rift valley was deposited tillites by glaciers of the Gondwana continent under grip of refrigeration. Along with the glacigene conglomerates were emplaced diamictites generated by submarine slides triggered, presumably, by earthquakes originating from faults delimiting the rift. The diamictities are admixed with lava, agglomerate and tuff, indicating widespread volcanism in the rift valley. The rifting culminated in the breaking away of the Tibetan part of the Himalaya in the Late Permian and formation of Neotethys between the Gondwanaland and the Cimmerian microcontinent embodying Tibet, Iran and Turkey. Rivers of the northern Peninsular India flowed in the northerly directions since the Middle Proterozoic through Early Eocene. In the Late Eocene there was a drastic drainage reversal to south and southeast when the Himalaya emerged in the northern front of the Gondwanaland.
Key words: Pan-African diastrophism, rift-related volcanism, Neotethys, drainage reversal, emergence of Himalaya.
Northern Submergent Platform The Vindhyan Basin of the Purana temporal span extends northward (Fig. 1) embodying in its broad expanse the 13000m thick succession of sedimentary rocks of the Lesser Himalaya (Krishnan and Swaminath, 1959; Valdiya, 1969). The Purana span stretches from the early Middle Proterozoic to the end of Early Cambrian (Valdiya, 1995). The sedimentary successions of the cratonic-interior basins such as Chhattisgarh, Pakhal, Cuddapah, Bhima and Kaladgi of the mainland Indian Gondwana are homotaxial with the Lesser Himalayan sedimentary rocks divisible into the Rautgara, Deoban, Mandhali formations and their equivalents (Valdiya, 1964, 1969, 1995). The homotaxis is evident from strong analogies of lithological sequences, basic volcanism contemporaneous with terrigenous sedimentation and characteristics and zonation of stromatolite assemblages in the carbonates of the Lesser Himalayan, Vindhyan and Aravalli regions. Indeed the Himalayan province represents the northern submergent platform (Fig. 1 ) of the Peninsular India belonging to East Gondwanaland.
End of Purana Era: Pan-African Upheaval The protracted Purana cycle of sedimentation ended towards the close of the Early Cambrian throughout the Peninsular India
and the Lesser Himalayan domains, but there was a pronounced interruption in basin-filling in the Tethyan realm in the northern margin. The sea thus vacated the Indian subcontinent completely. The whole of the Gondwanic India was evidently lifted up above sea water, presumably as a consequence of a large-scale diastrophism. This crustal movement is manifested in the emplacement of 500 f25 Ma old (Cambro-Ordovician) granites occurring extensively in the Lower Proterozoic metamorphic rock successions throughout the Himalaya, including the northern upwarped front close to the India-Asia junction. It is this tectonothermal event that put an end to nearly 1600 Ma long cycle of sedimentation (Valdiya, 1995). It is recognized as the Pan-African orogeny in the Gondwanaland. The Pan-African granites possibly belong to the 10,000 km long girdle of Cambro-Ordovician granites embracing Afghanistan, Himalaya, Australia and Antarctica (Le Fort et al., 1986) which formed the supercontinent Gondwanaland (Fig. 2). The Peninsular Indian part of the Gondwanaland did not escape the impacts of the Pan-African orogeny. In southwestern Rajasthan there was an intrusion of 510 f 10 Ma granite at Sendra (Gangopadhyay and Lahiri, 1986), and southern Kerala witnessed major invasion of alkali granite and syenite 750 to 450 Ma ago (Santosh and Drury, 1988). Molybdenites within the alkali granite at Ambalavayal give more precise age of 567
Fig.1.
Puma Sea, embracing the Vindhyan, Delhi and Manvar basins, extended north to encompass the Himalayan province (From Valdiya, 1997).The Himalaya province was indeed the northern platform of the Gondwanic Indian Shield.
HFF- H i m a l a y a n F r o n t a l F a u I t , M B T - M a i n Boundary T h r u s t , M C T - M a i n C e n t r a l T h r u s t .
G r a n i t e s of H i m alaya
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
-
4
5
Y
MAIN CENTRAL THRUST
,
....- - .
AG E ( M.y.)
.h
U . f r l s i c volcanism =Himalayan
front
Fig. 2. 500 f 25 Ma old granites of thc 1 Iimalayan province (After Valdiya, 1995)presumably belonged to the 10,000km long girdle of Pan-African granites of the supercontinental Gondwana (After LeFort et al., 1986).
Ma (Santosh et a]., 1994) to this tectonothermal event in southern India, which caused widespread granulite metamorphism around 550 Ma south of the Palghat-Cauvery Shear Zone (Menon and Santosh, 1995), and the formation of incipient charnockite around 550 15 Ma at Ponmudi (Choudhary et a]., 1992). The whole of the Indian part of the East Gondwanaland thus experienced a tectonothermal phenomenon of great moment and consequence.
*
Return of the Sea: Hercynian Diastrophism The sea returned in the Early Permian along a narrow elongatedepression that was formed due to subsidenceor rifting down of the crust along what is today the Outer (Southern) Gondwana Researcli. V I , No. 1, 1997
Lesser Himalaya (Valdiya, 1995).It was a graben of sorts, and stretched from the Salt Range in northern Pakistan through Pir- Panjal in Kashmir to eastern Arunachal Pradesh. The incursion of the sea took place in the Central India also (Fig. 3) through Rajhara in Bihar, Manendragarh-Umariain Madhya Pradesh and Bap and Badhaura in western Rajasthan. In the Peninsular India grabens were formed in the belts now occupied by the rivers Damodar, Mahanadi, Godavari and Narmada. The rifting is related to the extension (stretching) of the Indian Shield. In these rift valleys of the Outer Lesser Himalaya and Central India were deposited tillites - the Talchir Boulder Beds. The debris were dumped by glaciers of the Gondwana continent under grip of severe glaciation. The boulder conglomerate at
6
K.S. VALDIYA
irmada
Marine incursion (mixed sediments)
Fig. 3. Marine incursion in southern belt of the Himalaya in the Early Permian took place possibly through rift valleys in the Indian Shield (After Chatterjee and Hotton, 1986).
Tobra in the Salt Range (Pakistan) as well as at Bap and Badhaura in Marwar, contain clasts of Malani Rhyolite and Erinpura Granite (Gee, 1989). Obviously, the glaciers then covering the Aravalli extended northward as far as the Salt Range more than 600 km away. The marine shales associated with tillites contain, among other fossils, such cold-loving animals as Eurydesma and Deltopecten all along the basins. The contribution of the melt water from glaciers was reponsible for the cooling of sea water. In the Lesser Himalayan domain along with tillites and greywackes were emplaced diamictites generated by submarine slides and resultant turbidity currents (Jain, 1981;
Dhital, 1992), presumably triggered by earthquakes originating in faults that delimit the rift valley. The diamictites are admixed with agglomerate and tuff in the upper part (Fig. 4) indicating onset of explosive volcanism along the lines of rifting. These grabens of the Peninsular India as well as Outer Lesser Himalaya were gradually filled up with terrigenous sediments brought by rivers and streams which had become very active after the melting away of the ice cover. The rivers flowed in the NW, N and NE directions (Casshyap and Tewari, 1981; Sakai, 1991). Evidently, the continental margin of the Gondwanic Indian Shield continued to slope northwards in even the Late Palaeozoic and Early Mesozoic (Valdiya, 1997) as it used to all through the Proterozoic and Palaeozoic eras. The rivers spread sheets of sand, silt and clay on their flood plains, and buried forests of Gangamopteris and Glossopteris flora in swamps and oxbow lakes where they grew luxuriantly. The burial of the plants gave rise to rich seams of coal, as seen in Central India and in the Eastern Himalaya east of the Arun river.
Volcanism and Rifting of Himalayan Province Volcanoes became active all along the Outer Lesser Himalaya in the Early Permian. The lavas welled out possibly through deep faults formed due to rifting of frontal part of the Indian crust (Baud et al., 1984; Bhat, 1987). Consequently, a chain of volcanoes - represented by the Panjal Volcanics formed. It stretched from Shahbazgarha in northern Pakistan (Pogue et al., 1992) through Pir Panjal in Kashmir (Wadia, 1934),Bhaderwah-Chamba in western Himachal, the DugaddaRathwadhab belt in southern Garhwal (Middlemiss, 1885; Valdiya, 1980), the Tansen Hills in southcentral Nepal (Sakai,
Productus Limestone Zewan Formation
Late Permian
-. -.-. . -.- .- . -
_.-.-
-
Nishatbagh Formation (Gangamopteris B e d )
v
v
Early Permian
v
Agglomeratic S l a t e Tobra Conglomerate (Glacial)
mityEa r ly Carboniferous
F e n e s t e l l a Shale Syringothyris L s t .
t: ' : : : I
: :' :' : :'
1
14
-I
Fig. 4. Glacial tillite, colluvial diamictite and volcanic agglomerate interbedded and interfingering with marine sediments of Early Permian age and with basaltic lava as typically seen in the Pir Panjal, Kashmir (From Valdiya, 1997).
Gondwana Research, V l , No. I , 1997
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
1989, 1991), Barahkshetra in southeastern Nepal (Bashyal, 1980),Rangit Valley in southern Sikkim and Bhutan (Acharyya, 1973) to Igo-Jirdo in eastern Arunachal (Jain, 1981). The 284 k 1 Ma old dykes of alkali granite cutting through the sedimentary succession in southcentral Zanskar and adjoining Lahaul in the Tethyan domain (Spring et al., 1993)demonstrate that the Himalayan crust had indeed stretched in the Early Permian, leading to the development of the rift valley. Volcanic activities continued intermittently through Late Triassic in the Pir Panjal and Zanskar to Early Cretaceous in the Sindhu valley in Ladakh, the southern slope of Annapurnan and Sagarmatha in northern Nepal and in the Tansen Hills in southcentral Nepal.
Breaking Away of Northern Front The fissuring of the Himalayan province accompanied by volcanism and marine incursion along the grabens imply that the Gondwanic Indian Shield was once again overtaken by a powerful crustal movement, leading eventually to the breaking away of the northern part of the continent. Tibetan landmass along with Iran and Turkey -forming what has been described as the Cimmerian microcontinent - broke away and a new sea known as Neotethys emerged between the Indian Gondwana and the Cimmeria (Sengor, 1984). This sea was linked with
7
the Mediterranean Tethys (Fig. 5). Early separation of Tibet from mainland Gondwanic India explains the common ocurrence in the sediments of flora of Cathaysian affinity in Kashmir and southern Tibet (Singh et al., 1982).
Drastic Reversal of Drainage The Late Cretaceous plant fossils in the Taltung section of the Tansen Hills in southcentral Nepal strikingly resemble the fossil flora of the Rajmahal Hills in eastern Bihar (Sakai, 1989). It seems that the northward-flowing rivers that drained the upland of Santhal Pargana carried plant debris along with sediments and deposits not only in the Taltung area but also in the far northern tract - in Kagbeni, Kangpa and Lingshi basins (Fig. 6) in the Tethyan shore (Valdiya, 1997). The rivers of northern Peninsular India continued to flow in the northerly and northwesterly directions until Eocene 63 to 40 Ma ago. Then there was a drastic drainage reversal to the southeast and south (Valdiya, 1997). In the Hi’machal sector (Fig. 7) the rivers started flowing southwards (Srivastava and Casshyap, 1983) and in the Pakistan sector eastwards (Waheed and Wells, 1990). Obviously, by the Late Eocene time an orogen called Himalaya had emerged in the northern front of the Gondwanaland and started growing higher and higher (Valdiya, 1997).
ate Permian Fig. 5. Breaking away of the Tibetan microcontinent from the Indian Gondwanaland opened up a seaway called ‘Neotethys’ in the Later Permian (Based on Sengor, 1984).
Gondwana Research, V l , No. I , 1997
8
K.S. VALDIYA
Saga r m a t h a Lhotse 1 I Everest Limestone
Chobuk
Everest Petitese
E v e r e s t Pelites
Lachi F m ( Permian)
MBT
P a lp a
Phari F m (Jurassic)
Ta n sen
m 1000 0
Taltung f luvial sediments
P I with Aulis volca nics
r]
1 . 1---
Bansi( AmiIe)(PaIaeocene) Subathu( Bbainskoti) ( M i d d l e Eocene)
Murree (Dumri)
d?b
S isne d i a m i c t i t e s ( Lr P e r m i a n )
\
Flora transported NWjN,NE
Fig. 6 . Later Cretaceous rivers draining the Rajmahal Hills (eastern Bihar) in the Peninsular Indian Shield flowed northwards and deposited plant debris along with sediments in the distal Tethyan realm (From Valdiya, 1997, based on various sources). Gondwana Research, V I , No. I , 1997
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
Fig. 7. Drastic reversal of drainage in the Later Eocene. The northward and northwestward flowing rivers gave way to south- and southwest-flowing rivers and streams as the Himalaya emerged from the cradle of the sea (From Valdiya, 1997).
References Acharyya, S.K. (1973) Late Palaeozoic glaciation vs. volcanic activity along the Himalayan chain with special reference to Eastern Himalaya. Himalayan Geology, v. 3, pp. 209-230. Bashyal, R.P. (1980) Gondwana-type of formation with phosphatic rocks in SE Nepal. J. Geol. SOC.India, v. 21, pp. 484-491. Baud, A., Gaetani, M., Garzanti, E., Fors, E., Nicora, A. and Tintori, A. (1984) Geological observations in southeastern Zanskar and adjacent Lahaul area. Eclogae Geol. Helv., v. 77, pp. 171-197. Bhat, M.I. (1987) Spasmodic rift reactivation and its role in the preorogenic evolution of the Himalayan region, Tectonophys., v. 134, pp. 103-127. Casshyap, S.M. and Tewari, R.C. ( I 98 1) Depositional model and tectonic evolution of Gondwana basin. Palaeobotanist,v. 36, pp. 59-66. Chatterjee, S. and Hotton, N. (1986) The palaeopositions of India, J. Southeast Asian Earth Sci.,v. 1, pp. 145-189. Choudhary, A.K., Harris, N.B.W., Clastern, P.V. and Hawkesworth, C.J. (1992) Pan-African charnockite formation in Kerala, India, Geol. Mag., v. 129, pp. 257-264. Dhital, M.R., 1992. Lithostratigraphic comparison of three diamictite successions of Nepal Lesser Himalaya, J. Nepal. Geol. SOC.,v. 8, pp. 43-54. Gangopadhyay, P.K. and Lahiri, A. (1986) Some problems of geochronology of Precambrian rocks in Rajasthan: An appraisal. Ind. J. Earth Sci.,v. 13, pp. 169-188. Gee, E.R. (1989) Overview of the geology and structure of the Salt Range with observations on related areas of northern Pakistan, Geol. SOC.Amer. Special Paper 232, Boulder, pp. 95-1 12. Jain, A.K. (1981) Stratigraphy, petrography and palaeogeography of the later Palaeozoic diamictites of the Lesser Himalaya. Sed. Geol.,v. 30, pp. 43-78. Krishnan, M.S. and Swaminath, J. (1959) The Great Vindhyan Basin of northern India. J. Geol. SOC.India, v. 1, pp. 10-30. LeFort, P., Debon, F., Pecher, A., Sonet, J. and Vidal, P. (1986) The 500-Ma magmatic event in Alpine- Southern Asia: A thermal
Gondwoncc Researclr. V l , No. I , 1997
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episode at Gondwana scale, Sci. de l’Terre, Memoir 47, CNRS, Paris, pp. 191-209. Menon, R.D. and Santosh, M. (1995) The Pan-African gemstone province of East Gondwana, Geol. SOC.India Mem., v. 34, pp. 357-37 1. Middlemiss, C.S. (1 885) A fossiliferous series in Lower Himalayas. Rec. Geol. Surv. Ind.,v. 18, pp. 73-77. Pogue, K.R., DiPietro, J.A., Khan, S.R., Hughes, S.S., Dilles, J.H. and Lawrence, R.D. (1992) Late Palaeozoic rifting in northern Pakistan. Tectonics, v. 11, pp. 871-883. Sakai, H. (1989) Rifting of the Gondwanaland and uplifting of the Himalayas recorded in Mesozoic and Tertiary fluvial sediments i n Nepal Himalayas, In: A. Taira and F. Masuda (Eds), Sedimentary Facies in the Active Plate Margin, Terra Pub. Co., Tokyo, pp. 723-732. Sakai, H. (1991) Gondwanas in Nepal Himalaya, In: S.K. Tandon et al. (Eds.), Sedimentary Basins of India, Gyanodaya Prakashan, Nainital, pp. 202-217. Santosh, M. and Drury, S.A. (1988) Alkali granites with PanAfrican affinities from Kerala, South India. J. Geol., v. 96, pp. 616-622. Santosh, M., Suzuki, K. and Masuda, A. (1994) Re-0s dating of molybdinites from southern India: Implications for Pan-African orogeny. J. Geol. SOC.Ind.,v. 43, pp. 585-590. Sengor, A.M.C. (1984) The Cimmeride orogenic system and tectonics of Eurasia. Geol. SOC.Amer. Special Paper 195, Boulder, 74p. Singh, Gopal, Maithy, P.K. and Bose, M.N. (1982) Upper Palaeozoic flora of Kashmir Himalaya, The Palaeobotanist, v. 30, pp. 185232. Spring, L., Bussy, F.,Vannay, J.C., Huon, S. and Cosca, M.A. (1993) Early Permian granitic dykes of alkaline affinity in the Indian High Himalaya of Upper Lahaul and SE Zanskar: Geochemical characterization and geotectonic implications, In: P.J. Treloar and M.P. Searle (Eds.) Himalayan Tectonics, Geol. SOC.,London, Sp. Pub. NO.74, pp. 251-264. Srivastava, V.K. and Casshyap, S.M. (1 983) Evolution of the preSiwalikTertiary Basin of Himachal Himalaya, J. Geol. SOC.India, V. 24, pp. 134-147. Valdiya, K.S. ( I 964) The unfossiliferous formations of the Lesser Himalaya and their correlation, Report 22nd Inern. Geol. Congr., Delhi, v. 11, pp. 15-36. Valdiya, K.S. (1969) Stromatolites of the Lesser Himalayan carbonate formations and Vindhyans, J. Geol. SOC.India,v. 10, pp. 1-25. Valdiya, K.S. (1980) Geology of the Kumaun Lesser Himalaya, Wadia Institute of Himalayan Geology, Dehradun, 29 1p. Valdiya, K.S. (1995) Proterozoic sedimentation and Pan-African geodynamic development in the Himalaya. Precam., Res., v. 74, pp. 35-55. Valdiya, K.S. (1997) Dynamic Himalaya. Universities Press, Hyderabad. Wadia, D.N. (1934) The Cambrian-Trias sequence of N.W. Kashmir, Rec. Geol. Surv. India, v. 68, pp. 121-176. Waheed, A. and Wells, N.A. (1990) Changes in palaeocurrents during the development of an obliquely convergent plate boundary, Sulaiman fold-belt, SouthwesternHimalaya, westcentral Pakistan. Sed. Geol., v. 67, pp. 237-261.
ISSN: 1342-937X
Himalaya, the Northern Frontier of East Gondwanaland K.S. Valdiya Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore - 560 064, India (Manuscript received January 9, 1997; accepted January 30,1997)
Abstract The Himalayan province, which represents the northern platform of the Peninsular India belonging to East Gondwanaland, was strongly affected by PanAfrican diastrophism 500f25 Ma ago. This brought to an end the protracted Purana cycle of sedimentation throughout the Peninsular India and the Lesser Himalaya and interrupted basin-filling in its northern Tethyan domain. But the sea returned in the Early Permian along a narrow depression formed due to rifting of the Himalayan crust in what is today the southern Lesser Himalaya. In the rift valley was deposited tillites by glaciers of the Gondwana continent under grip of refrigeration. Along with the glacigene conglomerates were emplaced diamictites generated by submarine slides triggered, presumably, by earthquakes originating from faults delimiting the rift. The diamictities are admixed with lava, agglomerate and tuff, indicating widespread volcanism in the rift valley. The rifting culminated in the breaking away of the Tibetan part of the Himalaya in the Late Permian and formation of Neotethys between the Gondwanaland and the Cimmerian microcontinent embodying Tibet, Iran and Turkey. Rivers of the northern Peninsular India flowed in the northerly directions since the Middle Proterozoic through Early Eocene. In the Late Eocene there was a drastic drainage reversal to south and southeast when the Himalaya emerged in the northern front of the Gondwanaland.
Key words: Pan-African diastrophism, rift-related volcanism, Neotethys, drainage reversal, emergence of Himalaya.
Northern Submergent Platform The Vindhyan Basin of the Purana temporal span extends northward (Fig. 1) embodying in its broad expanse the 13000m thick succession of sedimentary rocks of the Lesser Himalaya (Krishnan and Swaminath, 1959; Valdiya, 1969). The Purana span stretches from the early Middle Proterozoic to the end of Early Cambrian (Valdiya, 1995). The sedimentary successions of the cratonic-interior basins such as Chhattisgarh, Pakhal, Cuddapah, Bhima and Kaladgi of the mainland Indian Gondwana are homotaxial with the Lesser Himalayan sedimentary rocks divisible into the Rautgara, Deoban, Mandhali formations and their equivalents (Valdiya, 1964, 1969, 1995). The homotaxis is evident from strong analogies of lithological sequences, basic volcanism contemporaneous with terrigenous sedimentation and characteristics and zonation of stromatolite assemblages in the carbonates of the Lesser Himalayan, Vindhyan and Aravalli regions. Indeed the Himalayan province represents the northern submergent platform (Fig. 1 ) of the Peninsular India belonging to East Gondwanaland.
End of Purana Era: Pan-African Upheaval The protracted Purana cycle of sedimentation ended towards the close of the Early Cambrian throughout the Peninsular India
and the Lesser Himalayan domains, but there was a pronounced interruption in basin-filling in the Tethyan realm in the northern margin. The sea thus vacated the Indian subcontinent completely. The whole of the Gondwanic India was evidently lifted up above sea water, presumably as a consequence of a large-scale diastrophism. This crustal movement is manifested in the emplacement of 500 f25 Ma old (Cambro-Ordovician) granites occurring extensively in the Lower Proterozoic metamorphic rock successions throughout the Himalaya, including the northern upwarped front close to the India-Asia junction. It is this tectonothermal event that put an end to nearly 1600 Ma long cycle of sedimentation (Valdiya, 1995). It is recognized as the Pan-African orogeny in the Gondwanaland. The Pan-African granites possibly belong to the 10,000 km long girdle of Cambro-Ordovician granites embracing Afghanistan, Himalaya, Australia and Antarctica (Le Fort et al., 1986) which formed the supercontinent Gondwanaland (Fig. 2). The Peninsular Indian part of the Gondwanaland did not escape the impacts of the Pan-African orogeny. In southwestern Rajasthan there was an intrusion of 510 f 10 Ma granite at Sendra (Gangopadhyay and Lahiri, 1986), and southern Kerala witnessed major invasion of alkali granite and syenite 750 to 450 Ma ago (Santosh and Drury, 1988). Molybdenites within the alkali granite at Ambalavayal give more precise age of 567
Fig.1.
Puma Sea, embracing the Vindhyan, Delhi and Manvar basins, extended north to encompass the Himalayan province (From Valdiya, 1997).The Himalaya province was indeed the northern platform of the Gondwanic Indian Shield.
HFF- H i m a l a y a n F r o n t a l F a u I t , M B T - M a i n Boundary T h r u s t , M C T - M a i n C e n t r a l T h r u s t .
G r a n i t e s of H i m alaya
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
-
4
5
Y
MAIN CENTRAL THRUST
,
....- - .
AG E ( M.y.)
.h
U . f r l s i c volcanism =Himalayan
front
Fig. 2. 500 f 25 Ma old granites of thc 1 Iimalayan province (After Valdiya, 1995)presumably belonged to the 10,000km long girdle of Pan-African granites of the supercontinental Gondwana (After LeFort et al., 1986).
Ma (Santosh et a]., 1994) to this tectonothermal event in southern India, which caused widespread granulite metamorphism around 550 Ma south of the Palghat-Cauvery Shear Zone (Menon and Santosh, 1995), and the formation of incipient charnockite around 550 15 Ma at Ponmudi (Choudhary et a]., 1992). The whole of the Indian part of the East Gondwanaland thus experienced a tectonothermal phenomenon of great moment and consequence.
*
Return of the Sea: Hercynian Diastrophism The sea returned in the Early Permian along a narrow elongatedepression that was formed due to subsidenceor rifting down of the crust along what is today the Outer (Southern) Gondwana Researcli. V I , No. 1, 1997
Lesser Himalaya (Valdiya, 1995).It was a graben of sorts, and stretched from the Salt Range in northern Pakistan through Pir- Panjal in Kashmir to eastern Arunachal Pradesh. The incursion of the sea took place in the Central India also (Fig. 3) through Rajhara in Bihar, Manendragarh-Umariain Madhya Pradesh and Bap and Badhaura in western Rajasthan. In the Peninsular India grabens were formed in the belts now occupied by the rivers Damodar, Mahanadi, Godavari and Narmada. The rifting is related to the extension (stretching) of the Indian Shield. In these rift valleys of the Outer Lesser Himalaya and Central India were deposited tillites - the Talchir Boulder Beds. The debris were dumped by glaciers of the Gondwana continent under grip of severe glaciation. The boulder conglomerate at
6
K.S. VALDIYA
irmada
Marine incursion (mixed sediments)
Fig. 3. Marine incursion in southern belt of the Himalaya in the Early Permian took place possibly through rift valleys in the Indian Shield (After Chatterjee and Hotton, 1986).
Tobra in the Salt Range (Pakistan) as well as at Bap and Badhaura in Marwar, contain clasts of Malani Rhyolite and Erinpura Granite (Gee, 1989). Obviously, the glaciers then covering the Aravalli extended northward as far as the Salt Range more than 600 km away. The marine shales associated with tillites contain, among other fossils, such cold-loving animals as Eurydesma and Deltopecten all along the basins. The contribution of the melt water from glaciers was reponsible for the cooling of sea water. In the Lesser Himalayan domain along with tillites and greywackes were emplaced diamictites generated by submarine slides and resultant turbidity currents (Jain, 1981;
Dhital, 1992), presumably triggered by earthquakes originating in faults that delimit the rift valley. The diamictites are admixed with agglomerate and tuff in the upper part (Fig. 4) indicating onset of explosive volcanism along the lines of rifting. These grabens of the Peninsular India as well as Outer Lesser Himalaya were gradually filled up with terrigenous sediments brought by rivers and streams which had become very active after the melting away of the ice cover. The rivers flowed in the NW, N and NE directions (Casshyap and Tewari, 1981; Sakai, 1991). Evidently, the continental margin of the Gondwanic Indian Shield continued to slope northwards in even the Late Palaeozoic and Early Mesozoic (Valdiya, 1997) as it used to all through the Proterozoic and Palaeozoic eras. The rivers spread sheets of sand, silt and clay on their flood plains, and buried forests of Gangamopteris and Glossopteris flora in swamps and oxbow lakes where they grew luxuriantly. The burial of the plants gave rise to rich seams of coal, as seen in Central India and in the Eastern Himalaya east of the Arun river.
Volcanism and Rifting of Himalayan Province Volcanoes became active all along the Outer Lesser Himalaya in the Early Permian. The lavas welled out possibly through deep faults formed due to rifting of frontal part of the Indian crust (Baud et al., 1984; Bhat, 1987). Consequently, a chain of volcanoes - represented by the Panjal Volcanics formed. It stretched from Shahbazgarha in northern Pakistan (Pogue et al., 1992) through Pir Panjal in Kashmir (Wadia, 1934),Bhaderwah-Chamba in western Himachal, the DugaddaRathwadhab belt in southern Garhwal (Middlemiss, 1885; Valdiya, 1980), the Tansen Hills in southcentral Nepal (Sakai,
Productus Limestone Zewan Formation
Late Permian
-. -.-. . -.- .- . -
_.-.-
-
Nishatbagh Formation (Gangamopteris B e d )
v
v
Early Permian
v
Agglomeratic S l a t e Tobra Conglomerate (Glacial)
mityEa r ly Carboniferous
F e n e s t e l l a Shale Syringothyris L s t .
t: ' : : : I
: :' :' : :'
1
14
-I
Fig. 4. Glacial tillite, colluvial diamictite and volcanic agglomerate interbedded and interfingering with marine sediments of Early Permian age and with basaltic lava as typically seen in the Pir Panjal, Kashmir (From Valdiya, 1997).
Gondwana Research, V l , No. I , 1997
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
1989, 1991), Barahkshetra in southeastern Nepal (Bashyal, 1980),Rangit Valley in southern Sikkim and Bhutan (Acharyya, 1973) to Igo-Jirdo in eastern Arunachal (Jain, 1981). The 284 k 1 Ma old dykes of alkali granite cutting through the sedimentary succession in southcentral Zanskar and adjoining Lahaul in the Tethyan domain (Spring et al., 1993)demonstrate that the Himalayan crust had indeed stretched in the Early Permian, leading to the development of the rift valley. Volcanic activities continued intermittently through Late Triassic in the Pir Panjal and Zanskar to Early Cretaceous in the Sindhu valley in Ladakh, the southern slope of Annapurnan and Sagarmatha in northern Nepal and in the Tansen Hills in southcentral Nepal.
Breaking Away of Northern Front The fissuring of the Himalayan province accompanied by volcanism and marine incursion along the grabens imply that the Gondwanic Indian Shield was once again overtaken by a powerful crustal movement, leading eventually to the breaking away of the northern part of the continent. Tibetan landmass along with Iran and Turkey -forming what has been described as the Cimmerian microcontinent - broke away and a new sea known as Neotethys emerged between the Indian Gondwana and the Cimmeria (Sengor, 1984). This sea was linked with
7
the Mediterranean Tethys (Fig. 5). Early separation of Tibet from mainland Gondwanic India explains the common ocurrence in the sediments of flora of Cathaysian affinity in Kashmir and southern Tibet (Singh et al., 1982).
Drastic Reversal of Drainage The Late Cretaceous plant fossils in the Taltung section of the Tansen Hills in southcentral Nepal strikingly resemble the fossil flora of the Rajmahal Hills in eastern Bihar (Sakai, 1989). It seems that the northward-flowing rivers that drained the upland of Santhal Pargana carried plant debris along with sediments and deposits not only in the Taltung area but also in the far northern tract - in Kagbeni, Kangpa and Lingshi basins (Fig. 6) in the Tethyan shore (Valdiya, 1997). The rivers of northern Peninsular India continued to flow in the northerly and northwesterly directions until Eocene 63 to 40 Ma ago. Then there was a drastic drainage reversal to the southeast and south (Valdiya, 1997). In the Hi’machal sector (Fig. 7) the rivers started flowing southwards (Srivastava and Casshyap, 1983) and in the Pakistan sector eastwards (Waheed and Wells, 1990). Obviously, by the Late Eocene time an orogen called Himalaya had emerged in the northern front of the Gondwanaland and started growing higher and higher (Valdiya, 1997).
ate Permian Fig. 5. Breaking away of the Tibetan microcontinent from the Indian Gondwanaland opened up a seaway called ‘Neotethys’ in the Later Permian (Based on Sengor, 1984).
Gondwana Research, V l , No. I , 1997
8
K.S. VALDIYA
Saga r m a t h a Lhotse 1 I Everest Limestone
Chobuk
Everest Petitese
E v e r e s t Pelites
Lachi F m ( Permian)
MBT
P a lp a
Phari F m (Jurassic)
Ta n sen
m 1000 0
Taltung f luvial sediments
P I with Aulis volca nics
r]
1 . 1---
Bansi( AmiIe)(PaIaeocene) Subathu( Bbainskoti) ( M i d d l e Eocene)
Murree (Dumri)
d?b
S isne d i a m i c t i t e s ( Lr P e r m i a n )
\
Flora transported NWjN,NE
Fig. 6 . Later Cretaceous rivers draining the Rajmahal Hills (eastern Bihar) in the Peninsular Indian Shield flowed northwards and deposited plant debris along with sediments in the distal Tethyan realm (From Valdiya, 1997, based on various sources). Gondwana Research, V I , No. I , 1997
HIMALAYA, THE NORTHERN FRONTIER OF EAST GONDWANALAND
Fig. 7. Drastic reversal of drainage in the Later Eocene. The northward and northwestward flowing rivers gave way to south- and southwest-flowing rivers and streams as the Himalaya emerged from the cradle of the sea (From Valdiya, 1997).
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