Geotraverses through Higher and Tethyan zones of Lahaul and Spiti sector of N-W Himachal and adjoining part of Ladakh Himalaya Anshu K. Sinha
Sinha AK 1998. Geotraverses through Higher and Tethyan zones of Lahaul and Spiti sector of N-W Himachal and adjoining part of Ladakh Himalaya. Palaeobolanisl 47: 1-15.
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 horizomal 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 confirms 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. Key words- Geotraverses, Tectonics, Lahaul-Spiti Sector, Ladakh Himalaya.
Anshu K. Sinha, Birbal Sahni Inslilule 0/Palaeobolany, 5] Universily Road, Lucknow 226007, India.
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~ ~ ~ ~ ~ ~ ft~ ~ ~-fmij ~ ~'Vf~ ~ ~ ~ Cfll~W~~'Hhl:? ~ ~ C1cll ~ ~ ~ ~ ~ lfR:i\~~ (~) 3N~ ~ 'g I TW'l tl'R fil1.P1 ~ ~ ~ ~"lC1~ ~ ~ ~ ~~<1g'~'1V ~ ~ ~ ~ ' ~ ~ ft~ ~ ~ ~ ~e>'lfcR~ ~Q'U1~ ~ ~ g& ffifl~It1'R-~ii ~ ~ ~ ~ ~ ~ ~ ~ ~ WE have been concentrating to systematically geological informations. undertake the geotraverses in the higher region Geotraverse 1. Along the deep gorge of Satluj of northwestern Himalaya covering the higher Valley : Rampur Jeori zone of Himalayan region of Himachal Pradesh Bhabanagar Wangtu-Akpa and partly the Ladakh region of Jammu and Pooh-Khab; along Spiti River up Kashmir. For this the following geotraverses were to Khab-Chango/Sumdo (Text taken to cover the maximum topographical and figure 1 & 2) (Plate 1). 2 THE PALAEOBOTANIST LEH Choqlamsar 9S t -..,·...... 1 475km(3505Ml:f"1 Upshi(3,384M) 424km. 1/ ~_.-Area of R~se(ir: Hemis , L TIl: ~-.T anq)anq - a "'--.(...... ' -' " (5.360Ml 364km. r .~_I\~ t .'/ j ~." > ( INDIA ~~ j \./ I D I SARCHU o PA TSEO 14253M1 l38H~SURAJ TAL ~ t 0 148001.1) ",,0"" X BARALACHA PASS / _..-,-<~0 DARCHA 148301.11 SPA EYLON8 o 1340~M) TOPKO YONGMA 13350~~ 146401.11 o ?:!-<:>,o~_\. ~ ~ ;:> ,_-:~\>-t CHANDRA TA SISSU '\. >; .<, ",,_':}.~~~(42701.1) 121301.1) ~ ",,"" KHOKSAR ::,-v !14079M) • OSAR • KIATO 139641.11. ,~- - ---, (/I .KIBBER BEAS KUND v'?o;. S' ~ / l NAGAR "I" C<:';'h,1.."" ,.,G'! • 1I760M1 C' >' :'" ~ • r~'" , \:~.l~ / ~AN ' '~ ,.:1 ~~ •CHITKUL (34501.1) 1/4. 8 ROHRU '<<'t!;'~ QSPQ fT. NARKAND A (~50M1 . ~" . '..:2;J 127091.1) JUBBAL ,;\HA TKOTI • KOTKHAI 118921.1)\. 111001.11 4115251.1) Text-figure I·Location l1lap of the area of research and the ground positions of geotraverses I, II, III & IV as described in the text in the NW Himalayas of Hinl.lch.t1 Pr.ldesh & Ladakh. SINHA-GEOTRAVERSES THROUGH H1GHER AND TETHYAN ZONES OF LAHAUL AND SPlTl Geotraverse II. Chota Shigri-Kunzum La-Kaja window of basic rock (Bhat & Le Fort, 1992), the (along Chandra & Spiti rivers) gneiss and mylonites are exposed up to the higher Himachal Himalaya in Bhabanagar Hydel project site. These rocks are Lahaul and Spiti (Text-figure 1 intruded by younger leucogranite of Himalayan & 3), (PI. 1 & 2). age (Sharma et ai., 1993). If we compare the Geotraverse III. Geotraverse along Pin and crystalline of Jutogh Formation in the Shimla Parahio valleys in Spiti region of hills, it looks in the root zone of Chail and Jutogh higher Himachal Himalaya tectonic units. Further upstream of the Satluj (Text-figure 1 & 4), (PI. 1 & 2) . gorge at the right bank of Wangtu Project, there Geotraverse IV. Geological Cross-section along are intrusions of profuse leucogranite apophyses Manali-Leh highway (covering and about 300 m from the bed of the river adjacent to the Bhabeh Hydro-electric project tunnel. the higher Himachal Himalaya as we across blue blades of Rohtang Pass (3980 m) across Further, come the of Chandra and Bhaga Valley kyanite and sillimanite bearing horizons the rocks th rough Key long-J ispa here are of very high grade. There are also Baralacha Pass- Larchung La amphibolitic sills visible within the gneissic rocks. As we proceed towards the Karcham upstream Pass- Taglang La-U pshi-Leh along the Satluj gorge, massive intrusives of (Text-figure 1 & 5(i) & (ii) granitic bodies along with amphibolite sills start (PI. 1,2 & 3). appearing. Between Wangtu and Karcham, there Geological description of these areas have is a clear-cut evidence of shear zones at the village been given by several workers like Stoliczka Tapri. The crystallines of Vaikrita (Griesbach, (1865), Hayden (1904), Berthelsen (1951, 1953), 1891; Sinha, 1989) zone are gneisses and mica schist Fuchs (1982), Srikantia (1981), Bhargava (1987), horizons and massive quartzitic zone between Bhargava and Bassi (1985, 1986), Herren (1987), Karcham and Pawari villages. The crushing of the Gaetani et al. (1990), Gaetani and Garzanti (1991), rock type before Pawari is indicative of a shear Garzanti (1991,1993), Garzanti and Frethe (1991), zone of thrust along the west bank of Satluj River. Spring and Blanc (1992), Spring (1993), Spring et The interspersed zone of quartzitic and gneissic ai. (1993), Steck et ai. (1993), Vannay (1993), rocks in the vicinity ofKalpa township, the capital Vannay and Steck (1995), Harris et ai. (1993), of Kinnaur and the hamlet of Pio Rest House, Fuchs and Linner (1995,1996), Rao et ai. (1982), produces very good soil for the healthy growth Powell and Conaghan (1973), Bhat and Le Fort of apple and grape orchards of high altitude (1992), Thakur (1992), Sinha (1989,1992,1997), variety. Further upstream traverses encounter a Sinha and Upadhyay (1997), Sinha and Mishra huge crushed Akpa granitic zones. These (1997). The detail information of the above leucogranites (Sharma et aI., 1993) indicate a very geotraverses are as follows: strong evidence of emplacement of granitic bodies Geotraverse I. of the younger Himalayan Tertiary age along the Along Satluj River Gorge and upstream axial zones of high grade higher Himalayan along its tributary Spiti River (Text figures 1 crystallines (Vannay & Grasemann, 1997; Walker & 2). et ai., 1997; Weinburg, 1997). Crossing the Shali-tectonic window, we come Proceeding further upstream across the across the klippe of Chail Formation in the Nirth Moorang village, there appears a tectonized zone synform. Here the gorge of Satluj River becomes near Spilo village and a low grade metamorphic narrower and as we traverse upstream the Rampur zone of Haimanta Group sequence. These 4 THE PALAEOBOTANIST horizons, composed of low grade metamorphic believe that the stratigraphic horizons discovered phyllites and quartzitic sandstone continue up to by Griesbach (1891) and Hayden (1904) are Pooh. Beyond Pooh, again the high grade remarkably homotaxial. Further upstream along crystalline appears and at Dabling a symmetrical the Spiti River, there is a clear stratigraphic anticlinal structure is exposed in the west bank of horizon of Permo-Carboniferous rocks with the Satluj gorge. The zone between Dabling and Khab lithology of light and dark shales and sandstones. looks to be highly disturbed and magmatically Further upstream of Spiti River from the intruded by young granites (Kwatra et al., 1993). Chango-Shalker Village, we continued along There also appears a typical appearance of dykes horizons of Permo-Carboniferous belts till Thabo swarms of leucogranitic intrusives evading the Monastry (PI. 2, fig. 2). From this locality, Birbal country rock. At Khab, the Satluj enters in the Sahni and Gothan (1937), H0eg et al. (1957) and Tibetan territory in the north-east region and the the author (AKS, 1985) discovered the Lower Spiti River joins with Satluj. Along the left bank Gondwana flora. From the collection made during of Spiti River there is a marked tectonic break the year 1985 from the same horizon of Po Series with the intruding leucogranites. The line of near Thabo Monastry Gothan and Sahni (1937) dislocation is clearly visible along the right bank reported for the first time some fossils of (PI. 4 & of Spiti and Lipak rivers near Yang Thang Rest 5) Rhacopteris. From the author's collection House at Maling Village. The tectonization and Maithy (Birbal Sahni Institute of Palaeobotany, crushing of the rock continue up to Chango Lucknow) identified the following species, viz., Village with the constant falling of boulders. Rhacopteris ovata (McCoy) Walkom and Earlier in 1904 in Hayden's map this fault was Triphyllopteris lecuriana J ongmann which clearly mapped, and at 1.31 p.m. 1ST on 19th reconfirm them to be of Lower Carboniferous January, 1975 it has been reactivated triggering age (PI. 4 & 5). an earthquake of magnitude 7 on Richter scale Geotraverse II. (Singh et al., 1975). Visibly this is the zone of active fault with constant falling of big boulders on the Chota-Shigri-Kunzum-La-Kaja higher road making impossible to drive and therefore it Himachal Himalaya in Lahaul and Spiti (Text also becomes difficult to maintain the road in good figures 1 & 3) (Plates 1 & 2). condition. Interestingly, at the Leo Village in the A few traverses were taken along the right right bank of Spiti River, an exposure of the bank of Chandrabhaga River after crossing limestone of Garbyang Formation (Sinha, 1989) Rohtang Pass (3980 m) (PI. 1, fig. 1; PI. 2, fig. 3). was observed which appear similar to the The Chota Shigri Glacier comes down from the limestone horizons of Malla J ohar. The high reaches of Central crystalline consisting of comparative study of the Haimanta and Martoli high grade metamorphic of Vaikrita Formation of Spiti and MalIa Johar (Sinha, 1989) makes us to and the snout with heavy morain against the PLATE 1 1. Bird-eye view ofKulu Valley looking from South; in the background at Rohtang Pass area. the Rohtang Pass (3980 m) snow capped high grade metamorphic 4. Tectonised zone of initial Tethyan Thnlst and subsequent South Central Crystalline Vaikrita High Himalaya Range. The monsoon Tibet Detachment (STD) between pile of Phanerozoic sediments. douds are intercepted by this range and causing the northern part of Higher Himalaya, a highland desert. 5. Exposure of Haimanta group of low grade metamorphic at the base 2. Monsoon clouds looming low over the Rohtang Pass (3980 m) area of sedimentary pile of Phanerozoic sediments. and blooming high altitude flora in the foreground. 6. Wide open valley of Spiti River with the exposure of Mesozoic 3. Contorted and ptygmatically folded high grade metamorphic rocks sediments on either side of the river bank. SINHA-GEOTRA VERSES THROUGH HIGHER AND TETHYAN ZONES OF LAHAUL AND SPITI 5 t 2 1 ,_ ~ " ~ '~..'~'~'---o~-.Jt·o 'lU,"'" ..., t - '"r" - ~W'!'!"~• '.h.fti . .,..,~__.~.. • ..,r1";' ;;..:.b'-- ,"t--' ...... , . -,' . ' , ;l -.' ...:,_.' -. ~ ti.T~~_,.~}.;l,,A} .' - ~~.. ,.....w~:'""" •'!t..~ ~'4 '• ~iit • <-" ..;, .;'\... • -....-. "" . ~. ":\' '0",..,.;.1' -:. ~ ~ r . ~~p1;.~~ o.~ '-to ilL .• t.;··~"~~~ .'~ .,..,.--.' ._;. . .,~-~>:t!i1'"-'''.' ••• ~, .'L,;, ... " Wi" .•' ....,. _ '" ..1- -.. ._ ' ...... ~.:• ..J''---.'" ,.,'" .. ./ ~/" ~~ ~.~-'!I;;;.'~.;(""";';- ,'.+~• ~...... ~~?,...... ( /;.. ~~'f .' _. ~'.\~, ._ • ,- \. \. _ "Ii:.~- . '\- 3 4 5 6 PLATE 1 6 THE PALAEOBOTANIST Chhatru Rest House situated on the right bank very wide (PI. 1, fig. 6, PI. 2, fig. 1) due to the of Chandra River. Since the Project work in the fluvio-glacial action. In the KabjimaNaia flowing Chota Shigri glacier is far away stream of Chandra down SW to join Spiti, there is a very interesting Valley hence, there is a suspension rope way exposure of Permo-Carboniferous rocks with the crossing line temporarily erected across the high flexural deformation (Text-figure 3) showing an torrent stream of Chandra River. Before Batal Rest apparent disconformity but without any distinct House, there is a marked tectonic contact between tectonic deformation. This horizon is important the high grade Vaikrita crystalline rocks and the in Himalaya which has been identified as the low grade Haimanta Formation (PI. 1, fig. 5). The Hercynian gap with the missing Carboniferous shear zone shows the sense of movement from rocks. It is represented by black slates and north to south followed by gravity slump of changing lithology with conglomerates having subsequent tectonic and orogenic movement. The silicious and argillite clasts in the argillaceous shear zone (PI. 1, fig. 4), visible over a distance of matrix. At Losar down stream in the Spiti Valley about 2 km, is also intruded by younger granitic (PI. 1 & 2), a thick horizon of Triassic rocks bodies. Moving up on the road from Batal Rest represented by alternating shale, silt and limestone House, the Lower Palaeozoic sedimentary layers (Balini & Krystyn, 1997; Garzanti, 1993; sequences are continuously exposed from the Bagati, 1990) is exposed. The river occupies a Kunzum La project across Chandra River up to gorgeous nature further down stream to Kaja near Kunzum La Pass (4520 m). This is an interesting Hansa onwards through Kioto Village. The section where one can try to search for the massive Jurassic horizons (Krishna et ai., 1997) Precambrian-Cambrian boundary; the occupy the higher gorge with distinct litho uninterrupted section of Lower Palaeozoic stratigraphic character and Megalodon bearing encompasses Ordovician, Silurian and Devonian fossils (PI. 2, fig. 5). The name of Kioto limestone rocks. It is interesting to note that here we also is derived after village Kioto (Hayden, 1904). came across the algal limestone of reefal origin of Traversing down stream from Kioto Village, Upper-Ordovician and Lower Silurian Period. before the village Pangma, it has been distinctly This horizon is comparable with the younger observed that the fold pattern in the Triassic limestone of MalIa Johar area (Sinha, 1989; Sinha horizon is disharmonic (PI. 2, figs 1 & 3). There et ai., 1996). The variegated nature of the Silurian are also younger folds disturbing both the Jurassic is very prominent in the multi-colour of rocks. and Triassic horizons before reaching Pangma, the The Devonian is very typical correlatable with contact between incompetent Triassic and the the both quartzite of Kashmir and Kumaun. The massive rocks; competent Jurassic rocks show a Spiti river which starts from the Kunzum La Pass tectonic contact. It is apparent that this movement flows down to Takche where a prominent must be along the stratigraphic contact but tributory Kabjima Nala joins with the main mobilized during the Himalayan orogenic stream of Spiti. The valley of Spiti River becomes movement. In the left bank of Spiti River, before PLATE 2 I. Wide open valley of Spiti River with {he exposure of Triassic and Triassic sediments. Jurassic rocks. Photo view looking {Owards east. 4. Camp·site In Parahio River Valley with rhe exposure of Lower 2. The famous village of Thabo with monastry and in the background Palaeozoic rocks in the background. the Upper Palaeozoic rocks are exposed from where the Lower 5. Exposure of massive pyramid like thick carbonate sequence of Carboniferous plant fossils were first recovered and described by Jurassic rocks with Megalodon fossils. Gothan & Sahni (1937). 6. The intraformational conglomerate formed with Ordovician and 3. The crossing of Parahio River by rope-bridge. The exposures are of Silurian fr.lgmems of algal limestones. SINHA-GEOTRA VERSES THROUGH HIGHER AND TETHYAN ZONES OF LAHAUL AND SPITI 7 1 2 3 4 6 5 PLATE 2 8 THE PALAEOBOTANIST Ki Monastry, the Cretaceous fossils appear at part of Cambrian conglomeratic horizons various higher reaches near Kibber and Chikim between conglomeratic and upper Ordovician (Singhetal., 1995). The magnificent disharmonic Silurian limestone shales (PI. 2, fig. 6). The folding is also possible all along the left bank of siltstones are white quartzite of Devonian ending Spiti River leading to Kaja. The Kaja is the up with the occurrence of Carboniferous and township and the capital of Spiti region having Permian Kuling beds (Fuchs, 1981). Pin River, the Government offices. Further down stream between Baldar and Sagnam, flows along a white along Spiti River, about 10 km at Attargoo the valley with considerable Quaternary debris on the Pin River joins the Spiti River. In the next either sides on the banks. Mud Village has been geotraverse (Text-figure 4) description we shall the type area of Muth quartzite of Spiti since early describe our next geotraverses from this upstream days research in this area (Hayden, 1904; Goel & along Pin River towards Bhabeh Pass and Nair, 1977). In new topo-sheet it has been shown tributary of Parahio River upstream towards that the Permian horizons of Kuling shale are Thango near the junction of Sumna Nala. exposed in the Kuling Village, nevertheless it is Geotraverse III. advisable that we should stick to the earlier nomenclature described in the literature, viz., Geotraverses along Pin and Parahio valleys Muth and Kuling (Berthelsen, 1953). in Spiti region high Himachal Himalaya (Text Coming down from the Thango of Parahio figures 1 & 4) (Plate 2) River (Text-figure 4) the classical and angular Down the Pin valley from the Bhabeh Pass unconformity of Cambrian and Ordovician rocks the Vaikrita high crystalline zone is succeeded by can be seen at the cross-section of Sumna nala the Haimanta low grade metamorphics. It has (described by Hayden, 1904). This is the classical been cited in the literature that there is a gradual unconformity established in the Tethyan realm passage of metamorphic gap from Vaikrita to of Himalaya which could be compared with the Haimanta (Hayden, 1904; Berthelsen, 1953). But type area of Cambrian and Ordovician in the the recent work along the Rohtang Pass (Text Atlantic coast of Wales, U.K. (author's figure 1) (PI. 1, 2 & 3) sector and the Satluj-Spiti observation during 1991 field work of IGCP rivers cross-sections have shown that there is a project 319) (Parcha, 1996). Here in Parahio distinct tectonic break with the sense of first Valley, the Cambrian-Ordovician is basically movement from N-S followed by subsequent represented by greenish siltstone and shaly normal gravity slump known as the South Tibet horizons. There are same horizons of Malla Johar Detachment (PI. 1, fig. 5) (STD) (Herren, 1987) young limestone of reefal origin (Sinha, 1989). The from Zanskar area. As we go down along the Pin Silurian horizons are basically represented by the Valley towards Sagnam (PI. 2, figs 3 & 4) where intra-formational conglomerate at the base Pin River joins the Parahio River (Sinha, et al., succeeded by fine grain limestone, siltstone and 1997, (see Text-figure 1 & 2), there is a marked shale essentially of deep red colour. Going along Lower Palaeozoic exposure including the upper the Parahio River stream on the left bank near PLATE 3 1. A bird eyeview of Ladakh mounrain range looking towards north 4. A view of Chitkan Nala in Lad.kh Himalaya having exposures of ,weSL The Indus gorge is in the foreground. ophiolitic melange in the background. View looking towards S-E. 2. Quaternary recent bke sediments in the Lamayuru area. 5. Another exposure of ophiolitic melange in the Indus gorge. 3. The Indus River Oowing from east ro West having molassic sediments 6. The exotic blocks in the Lamayura Flysch sediments near Mulbek of Miocene age on the left bank. Indus River marks the subduction Village (Krishna et al., 1997). zone of Indian and Eurasian plates. SINHA-GEOTRA VERSES THROUGH HIGHER AND TETHYAN ZONES OF LAHAUL AND SPITI 9 1 2 3 4 ,- ~.~. ~. . ~.:-~.' -~ ...... ~ '- ~ , .' . ~--"':---._~ ..--'-;l.,.---'. .... -.-...... -.. . e.~~ ,.~",-":;....,,;,,i '~-:"-t~'~.. ~":'..;.. J..i~, I ~.' ,'..-...-.,rl.' .....,~~'''~L-''''_. -- .:..' - : .. ~-~.l'f-~,:.'., - .~~,....,._, . \i--- . _ 5 6 PLATE 3 10 THE PALAEOBOTANIST the Gechang Village (PI. 2, fig. 4), white sugary It is interesting to note that due to strong quartzite of Muth of Devonian age is exposed permafrost action and the highland desert dipping NE 45°. Over the quartzite a black shale condition, formation of soil is very meagre horizon of Kuling is present. At this point due to resulting poor vegetation growth and plantation the steep slope, the Carboniferous horizon could activity. Recently, the Forest Department of not be located. Overlain by the silty beds the Himachal Pradesh has taken up a programme to Triassic horizon appears with the massive zone plant some special species in this area with partial of disharmonically folded layers of limestone, success. black shale sandstone and siltstone all along the Geotraverse IV. west bank of Parahio River down to Sagnam Geotraverse along Manali- U pshi-Leh Village (PI. 2, fig. 3) and Pokching and Mekin at highway through Higher Himachal and the junction of the Pin Parahio rivers at Mekin Ladakh Himalaya (Text-figures 1 & 5(i) & (ii)), Village on the left bank of Parahio River. Muth (Plate 3). white sugary quartzite is exposed in the core and Climbing up from Manali towards Rohtang anticlinal structure having Permian black Kuling Pass (3980 m) a continuous metamorphic rock shale and Lipak Formation of Lower sequence is visible changing in grade from chlorite Carboniferous (Fuchs, 1982). At the exposure, the biotite schist to granito-gneissic and biotite schist, Triassic horizon overlies the Permian Kuling there is a marked change in the metamorphic shale. The lower most part of the terrace shows grade ranging up to kyanite-sillimanite (PI. 1, fig. the algal stromatolitic growth which could not 3) grade near the Kothi Village where the Rohalla be identified as definite form for the determination Nala flows down demarcating geomorphological of age of this rock. The tectonic breaks of local change in the trend of rocks. Moving upwards nature between Kuling and Chhidang-Tokbo further towards Rohtang Pass, there is a huge villages may also be seen. These faults locally magmatic intrusion of Tertiary Leuco granite (PI. disturbed the Triassic horizons and near the camp 1, fig. 4) as well as Lower Palaeozoic granite of site of Chhidang Village, there appears the massive about 500 m.y. Besides downwards from the Megalodon limestone of Kioto Formation. The Rohtang Pass an inverted sequence (Wyss, 1997) Kioto limestone and the Triassic horizons are of marbolized limestone is exposed along the left imbricately folded and faulted as we proceed down bank of Chandra River having stratigraphic stream along the west bank of Pin River. At contact with the low metamorphic grade Anargoo (3375 m) Pin River finally meets the Spiti Haimanta rocks (See Text-figure 5). In literature, River and the massive limestone horizons of this limestone has been referred as Mesozoic Kioto-Jurassic Formation crosses towards NE having ammonoid fossils (Powell & Conaghan, over the Dankar Gompa (3850 m) and possibly 1973; Stecketal., 1993). Chandra and Bhaga rivers the Cretaceous horizons on the top of the cliff in ultimately meet together and called as NW (5720 m) which marks the northern end of Chandrabhaga River. This river flowing further the geotraverse (Text-figure 4). NW received water from various tributaries and PLATE 4 The photographs are all from untouched negatives. The original specimens are preserved at the Geological Survey of India, Calcutta. 1,2 Rhacoplcris ovala McCoy Walkom (= Rh. intequilalera Fstm. non 3, 4 Rhacopleris ovala McCoy Walkom (= Rh. irltequdawra Fstm. non Goepp.). From a bed "'·ith marine fosstls (Fenestella shales), '/2 mtle Goepp.). Thabo stage, 1'1. miles S.W. of TllJbo. Spiti. Fig. 3, nat. N. N.E. of Po, Spiti. Fig. I, n.\(. size; Fig. 2 x 2. K3/294 (P.lge 196). size; Fig. 4 x 2.K3I293 (Page 198). Vl Z :r: >- I Cl [TI ~ 0 -J ;:0 >- X < ~ [TI ;:0 Vl [TI Vl -J :r: ;:0 0c:: Cl:r: :r: Ci :r: [TI &:'" ;:0 >-z @ 0 +- -J [TI :r:-J ~ -< >- Z X N ~ 0 Z [TI Vl 0 ." r' :r:>- >-c:: r' >- Z 0 Vl ." :3 12 THE PALAEOBOTANIST is named as Chenab River. Traversing along the or Lower Palaeozoic age (Fuchs & Linner, 1995). Bhaga River beyond Keylong at Jispa in the low At the junction of Sarchu plain with the Tsarap grade metamorphics of the Haimanta Formation, River, the folded rocks give a very interesting a profuse intrusion of 500 m granites as well as picture of gravity folds and thrust slides. There Tertiary granites are present. These granitic bodies also appears a huge recombent fold in the NW are definite intrusives in the Precambrian and side of the road demarcating the massive Lower Palaeozoic Tethyan realm. Upstream fossiliferous rocks ofJurassic age (Text-figure 5(ii)). Bhaga River, at Sumdo Village, there is a The narrow gorge ends up at Pang camping site. pronounced tectonic dislocation marking the From there onwards, a wide stretch of more than extension feature fault of post-orogenic regime. 10 km of More Plain starts where one can drive From Darcha Village to Patseo Rest House, fine as one wishes without following the road track. grade siltstone and shaly rocks of visibly The majestic outcrops of Palaeozoic limestone and Ordovician character are exposed. Before reaching shaly horizon appear in the northwestern flang Ordovician character from camp site Zingzing bar up to Taglang La Pass. The Permian horizons wi th limestones are exposed below 5203 m high peak. (4883 m) the red colour sedimentary horizons of Climbing up Taglang La Pass it is obviously visible Silurian age starts appearing. At the contact of that the Lower Palaeozoics are metamorphosed Ordovician and Silurian rocks on the way of because there is no metamorphic break at this Baralacha La (5606- m) there appears reefal point. Fuchs and Linner (1995, 1996) have limestone of Caradocian. At the Baralacha, there predicted that here the rocks are part of Palaeozoic is a huge lake called Suraj Tal towards the source Tethyan sequence (Pi. 3, fig. 6). Going further of Bhaga River, whereas from the adjoining area down towards Gaya and Lata villages (Pi. 3, figs 1 of Chandra Tal, the Chandra River originates and & 3), there is an exposure of Palaeozoic rock as described earlier they meet at Tandi Village sequence which is truncated by a sharp fault zone making the prominent River called Chenab which at Lata comprising monotonous sequences of flows down through Jammu area to Pakistan Indus Flysch or trench sediment horizons (Pi. 3, making a tributory to Satluj and Indus River figs 1-5). This sequence is highly disharmonically System (Text-figure 1). The traverse then follows folded till Upshi where the Indus flows coming along Yunam River down the stream from across the intrusive Ladakh granites. Then the Kenlung Village (4531 m). The Yunam River typical trench of subduction zone of the Indian meets with the Tsarap River near Tingting Khur and Eurasian plates starts (PI. 3, fig. 3). The Village. The tectonics between Baralacha La and traverse then turns -towards Leh along the right Sarchu and Sarchu plain are highly complicated bank of Indus River and all along the river the because of local overthrusting phenomena of Ladakh granite and molasse sediments are exposed Devonian quartzite and black slate of Permo (Pi. 3). Carboniferous age. The Devonian Muth quartzite If one takes further geotraverse towards north forms a huge recumbent fold (Text-figure 5(i)). (Pi. 1, fig. 1) from Leh (Weinberg, 1997) one has There is an exposure of conglomeratic horizon to cross the Khardung La Pass (5569 m) situated between Baralacha Pass and Kenlung camp-site on the granitic and andesitic magmatic rocks; there (4531 m) which perhaps belongs to the Silurian onwards starts new orogenic cycles of Karakoram PLATES The photographs are all from untouched negatives. The original specimens dre preserved at the Geological Survey of India, Calculla. I, 2 Rhacopleris ovala McCoy Walkom (= Rh. iruequilalera Fstm. non 3,4 Rhacopleris ovala McCoy Walkom (= Rh. intequi!41era Fstm. non Goepp.). From a bed with marine fossils (Fenestella shales), \/, mile Goepp.). Thabo stage, 1V. miles S.W. of Thabo. Spiti. Fig. 3, nat. N. N.E. of Po, Spiti. Fig. I, nat. size; Fig. 2 x 2. K3/294 (Page 196). size; Fig. 4 x 2.K3/293 (Page 198). SINHA-GEOTRAVERSES THROUGH HIGHER AND TETHYAN ZONES OF LAHAUL AND SPITI 13 PLATES 14 THE PALAEOBOTANIST mountain. Part of the sequence between Leh and Bhargava ON & Bassi UK 1986. Silurian reefal build ups: Spiti Khalsar belongs to the back-arc sequences Kinnaur, Himachal Himalaya, India. Facies(Erlangen) 15 : 35-52. pertaining to the Karakoram mountain range are Bhat MI & Le Fort P 1992. Sm-Nd age and petrogenesis of Rampur described. (Sinha et al., 1997; Sinha et al. 1999). metavolcanic rocks, NW Himalaya: Late Archean relics in the Himalayan belt. Precamb. Res. 56: 191-210. ACKNOWLEDGEMENT Das M, Rao KGC, Roy AL & Narayana MS 1979. Bouguer, free During the course of geological traverses air and magnetic anomalies over Northwestern Himalayas. Ceo!. Surv. India, Misc. Pub/. 41(5) : 141-148. spanning about a decade, I have been assisted in Fuchs G 1982. The geology of the Pin Valley in the Spiti, H.P., field by Drs Dileep Mishra, Kuldip Bisht, Sudeep India. Ceo!.lb. Austrian Ceo!. Surv. Vienna 124 : 325-362. Paul and Bhupendra Rawat of Wadia Institute of Fuchs G & LinneI'M 1995. Geological traverse across the Western Himalayan Geology. Shri Prabhakar Dhasmana Himalaya- a contribution to the geology of eastern Ladakh, assisted me in ably word processing the Lahaul and Chamba.j. Ceol. 138(4) : 655-665. Fuchs G & LinneI'M 1996. On the geology of the Suture Zone manuscript. Shri Khattri and his colleagues in and Tso Morari Dome in eastern Ladakh (Himalaya). j. drawing section ofWIHG ably drafted the profile. Ceo!. 139(2) : 191-207. My former research fellows, Drs Rajeev Gaetani M & Garzanti E 1991. Multicyclic history of the northern Upadhyaya and Rakesh Chandra helped me in India continental margin (North-western Himalaya). AAPC BuLLetin75(9): 1427-1446. correcting the profile for final get-up. In Birbal Gaetani M, Garzanti E & Tintori A 1990. Permo-Carboniferous Sahni Institute of Palaeobotany (BSIP), to give a stratigraphy in SE Zanskar and NW Lahaul (NW final touch to paper, the help of Late Dr ].S. Antal, Himalaya, India). EcLogaegeo!. Helv. 83(1) : 143-161. Drs Mukund Sharma & Rajanikanth is Garzanti E 1991. Stratigraphy of the Early Cretaceous Giumal appreciated. I am grateful to the editorial and Group (Zanskar Range, northern India). Riv. ita!' Paleont. Stratigr. 97(3-4) : 485-510. drafting (Shri Bajpai) staff of BSIP and Museum Garzanti E 1993. Himalayan ironstones, "Superplumes", and the for Prof. Birbal Sahni's Plant reproduction. The breakup of Gondwana. Ceology 21 : 105-108. press has done appreciable job in reproducing the Garzanti E & Frethe MP 1991. Stratigraphic succession of the profiles. Thakkhola region (central Nepal) - Comparison with the Northwestern Tethys Himalaya. Riv. ita!' Paleonl. Stratigr. REFERENCES 97(1) : 3-26. Goel RK & Nair NGK 1977. The Spiti Ordovician-Silurian Bagati TN 1990. Lithostratigraphy and facies variation in the Spiti succession. Ceo!. Mem. Soc. India 18(1) : 47-48. Basin (Tethys), Himachal Pradesh, India. j. Him. Ceo!. 1 : Gothan W & Sahni B 1937. Fossil plants from the Po-Series of 35-47. 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