C&N&DIA.N AOURNAL OF EXPLORAITION GEOPHYSICS ““L, 30. NO, 2 ,DECEMBER 19941, P, 103~114

PETROLEUM GEOLOGY OF ’

OR. FRIEDENREICH*, O.L. SLIN$, U.M.S. PRADHAN~ AND R.B. SHRESTHA~

ARSTRACT 3.0 PROCEDURF. The project was a team effort consisting of Alconsult Magnetic.gravity and seisn1ic surveys, exIcnSi”e geological field mapping programs. StrUCtUlaland straiigraphic studies and professionals in the fields of geology, geophysics (seismic, prtr”le”m grochrmicill in”esligati”nshave her” carried““I in ,hr gravity), sedimentology, petrography and photogeology Trrai plains and the adjacent Siwalik Belt of southernNepal along with petroleum geochemists from the Geological sincethe lxc 1970s.This work. which hashem recentlyincorp ratedinto a comprehensiveevaluation. suggesrs that the countrylhas Survey of Canada and geologists from the Petroleum mrac,iYe petroleumpor,ihihties. Rockswith iignificam xn”rCe Exploration Promotion Project of Nepal. The work done by potential havebeen samplcd from oumops.and lhcmal modelling the team consisted of: a) reviewing all petroleum-related ruggcstshat, ill theprDspecli”r pm 01Ncpd ,hescpotential S,~“ICC rocksare in the oil andgas gmeration . Effective resewoirr information on Nepal and environs: b) collecting and analyr- Emcxpeccml to beloud in IhCt,.owcr Siwalik. S”rkhCI amI Condrana ing oil and gas seep samples; c) conducting field traverses sandrtoncsand in the carhonatci of the I.akharpata~Vindhyan throughout southern Nepal to collect samples for geochemi- G*O”p. cal and petrographic analyses; d) field mapping (structure) in Enpl”rati”n “pp”nunities in the Trrai include Stl”Cl”lrSilSS”Ci~ selected critical areas; e) studying the sedimentology 01 atedwith blind thrusts.hascment~con,rollcd drape and bull ~b’uc- potential reservoir rocks; and f) reviewing and interpreting twes, stratigraphic pinch-outs and suhcroptrapr. Major folds and thrustsin theSiwalik Fold Belt arelikely to providestr~ctwal traps. all the existing Nepal geophysical data. Ddling dcplh* to ohjeclivcs arc hm 150010 5000 mctrc* in the Teraiand from 25011fo 4000rncms in the Siwalik FoldBell. 4.0 DATA BASE

The data base included all previous work in which the PEPP/DMG was involved. This data included: a) more than 1.0 INTRonUCTloN IO years of geological field mapping (Schroeder, 19X I ; This paper is based on the recently completed Nepal Source Shrestha and Shrestha. 1983); b) a regional aeromagnetic and Seal Study conducted by Alconsult International Ltd. survey (CCC. 1980); c) a photogeological study (Hunting (AIL) and the Nepal Petroleum Exploration Promotion Project/ Geology and Geophysics Ltd., 1984); d) results of several Department of Mines and Geology (PEPP/DMG) HMG of geochemical investigations (Kay&ha, 1989): e) information Nepal (Slind, 1993). Geochemical sample collecting, labora- from the Shell Biratnagar I well; and f) basic field data and tory analysis, interpretation and modelling was conducted by interpretations from four geophysical surveys: 1983. I984 the Geochemistry Section of the Institute of Sedimentary and World BankKGG 1250 km reflection seismic program Petroleum Geology (ISPG) of the Geological Survey of (Harris, 19X4), 1987.1988 PClAClAirborne 1651 km retlec- Canada. The study operated under the overall direction of tion seismic and gravity program (Friedenreich and Slind. Petro-Canada International Management Services (PCTMS) for 1989), 1988-1989 Shell Nepal 1940 km (615 km used in this the Canadian International Development Agency. interpretation) reflection seismic program, 194 l-1993 French Government/CGG 422 km retlection seismic program. 2.0 OtSJECTtVE STUDY 5.0 GEoCnAPHICAL/GEoLoCICAI. SETTING The main objective of the study was to better understand the petroleum geology of Nepal and to define its oil and gas The , an independent country lying potential by combining existing data with new information between to the south and to the north (Figure I), acquired during the course of the study. is 800 km long from east to west and ranges in width from

‘Presented at the CSEGKSPG Joint Convention, Calgary. Alhem, May I I. 1994. Manuscript received hy the Editor October 17. 1W4; wised manuscripr received January 23, 19% 2AI~~n~~It lntrmationai Ltd.. 450.5X1 6th Avenue SW.. Calgary. Alhem T2P US2 ?HMG Nepal Petroleum Exploration Promorion Project. Dcpartmcnt of Mines and Geology. Kathmandu. Nrpai Thanks are given fo Psrro-Canada lnterna&mal Management Services. prqject managers for Canadian International Developmcnl Agmcy. and IO Lhc Pclmlcum Exploration Promotion Project ofthe Departmcm of Mines and Geology of His Majesty’s G,ovcmmen~ d Nepal Cur lhcir a~sisuncc in prcpring rhis paper.

ClECi 103 DccvlllbcrIV94 O.R. FKIEDENREICH. 0.L SLLND, U.M.S. PRADHAN and R.B. SHRESTHA

130 to 230 km. The country is naturally separated into four Group) thrust to the south (Parkash et al., 1980; Herail et al., major geographical/geological zones that parallel its long 1986). Gravity measurements and detailed field mapping indi- dimension (Frank and Fuchs, 1970; Mitchell, 1979; StRcklin, cate that the cores of at least some of these structures contain 1980; Windley, 1983). Each zone has its own characteristic pre-Siwalik rocks that are considered to be hydrocarbon explo- and structure and these zones are, from south to ration objectives (Friedenreich and Slind, 1989; Ebner, 1989). north, described below (Figures 2.3). The Siwalik Fold Belt and the are a pat of the fore- land of the (Parkash et al., 1980). They have 5.1 Terai some similarities with the foothills and western plains of The Terai is the Nepal portion of the Indo-Gangetic Plain Alberta and British Columbia and are the main areas of that extends from the Indian Shield in the south to the petroleum interest in Nepal. Siwalik Fold Belt to the north. The Plain is a few hundred metres above sea level and is underlain by a thick, relatively 5.3 Lesser Himal flat-lying sequence of Mid to Late Tertiary (Siwalik The Lesser Himal is a wide, stratigraphically and strut- Group) which unconformably overlies subbasins of early turally complex zone that lies immediately north of the Tertiary to sediments (Surkhet, Gondwana and Siwalik Fold Belt and is separated from it by the south-verging Vindhyan Groups) and igneous and metamorphic rocks of main boundaty (MBT). The majority of the Lesser Himal the Indian Shield (Agrawal, 1977; Acharyya and Ray, 1982; is composed of thrust sheets and of metasediments and Raivemun et al., 1983). The only deep well in Nepal (Shell igneous rock of the Midland Super Group. The Group is of Nepal B.V. Biratnagar 1, TD 3530 m in 1989) was drilled in little hydrocarbon exploration interest, although the oil and gas the far eastern part of the Terai. seeps of the Dailekh area occur within the Midland Group (CPIT, !973). These seeps are interpreted to have been gener- 5.2 Siwalik Fold Belt ated in sediments below the nappes (Figure 2). The Siwalik Fold Belt is from 5 to 45 km wide and rises abruptly from the Terai along the (MFT). It 5.4 Higher Himal consists of a series of ridges and valleys composed of thick The Higher Himal, which contains the spectacular peaks beds of folded and fault-repeated Tertiary molasse (Siwalik of the Great Himalayan Range, Everest, Annapuma, etc., is

- 80” 82” 84” 86”

30”

200km I I S-N: Approx. Location of Schematic Cross-Section Fig. 2

!6’ 0 : Biralnagar - 1 Well

82’ 84” 86’ 88” I I I I Fig. 1. Geological map of Nepal.

CIEC 104 December IV94 PETROLEUM CEOLOCY “t- PvEPAL thrust southward over the Lesser Himal by the main central not adequately dated, but is intcrprcted to be older than thrust (MCT; Figures I, 2). The zone is composed of a basal Carboniferous and to range well into the (Frank slab of metamorphic Proterozoic rocks overlain by a con- and Fuchs, 1970; StGcklin, 1980). formable sequence of to Tethyan sedi- Duilekh Group ~ The Dailekh Group, the lower part of ments (Bordet et al., 1981). Gas seeps occur in the upper the Midland Super Group, is made up of , garnetifer- Tethyan of northern central Nepal near the village of ous , feldspathic , volcanics and stroma- Muktinath (Figures 1.2). tolitic dolomites (Figures 2, 7). These rocks have been raised to the low green facies in the centre of the Midlands 6.0 STRATICRAPHY and the metamorphic grade increases in successive thrust sheets to the north (Mitchell, 1979; Bordet et al., 1981). The The following discussion concentrates only on those rock rocks of the Dailekh Group are not considered to bc cxplo- units that have a direct bearing on hydrocarbon exploration ration objectives. (Figure 3). Lakharpata Group ~ The Lakharpata Group occupies the Vindhyun Super Group ~ Vindhyan sediments, equiva- lent to those of the great Vindhyan Basin of Northern India, upper part of the Midland Super Group and, although not are interpreted to extend beneath the Ta% and Siwalik Fold firmly dated, is interpreted to be of Late Precambrian to Late Belt. The Vindhyan is reponed to have a maximum thickness Paleozoic ages (Stiicklin, 1980: Shrestha and Shrestha, of 5250 m (Agrawal, 1977; Srivastava et al., 1983) although 1983). It is unconformably overlain by frequently organic at least 12 000 m of pre-Tertiary seismic reflections have dark and of the Gondwana and Surkhet been observed under the Terai. The Vindhyen, which is con- Groups. This Group and its Vindhyan equivalent are an sidered to be a major hydrocarbon exploration objective, important exploration objective. consists of an unmetamorphosed sequence of stromatolitic The Group contains the following formations and mem- , and . Although dating is difficult, bers: the Vindhyan is considered to be equivalent to at least a part Sangram Fm: Greenish grey to black splintery shale, con- of the Lakharpata Group of the Lesser Himal. taining zones of relatively rich organic intervals (up to 9% Midland Super Group - The Midland Super Group, TOC); some shales being burned for fuel; major potential which encompasses most of the rocks of the Lesser Himal, is source rock:

tINDIA-+-NEPAL +.-----CHINA-

m ALLtJWUM SURKHET GP GRANITE m SIWALIK FM LAKHARPATA GP OPHlOLlTE

m GONDWANA GP m b;$@&,C ROCKS m VOLCANICS SEEPS “INDHYAN GP TETHYAN SEDIMENTS * HIGH GRADE BASEMENT METAMORPHIC ROCKS MFT MAN FRONTAL THRUST MET MAN BOUNDARY THRUST MCT MAIN CENTRALTHRUST MMT MA!NMANTLE THRUST

Fig. 2. Schematic cross-section through central Nepal

CIEG 105 Drcrmbr ,994 TERAI AND MAtNT;;;;y LESSER HIMAL SIWALIK FOLD BELT I PLIOCENE ;$$gi.z; UPPER v LOWER SURKHET GROUP (SW UPPER CRETACEOUS LOWER -k GONDWANA CRETACEOUS (GD) UPPER PALEOZOIC -I- UPPER (7) UPPER PALEOZOIC MtOCENE

LAKHdRPATA PALEOZOIC CRETACEOUS -GONDWANA TaOUP’ UPPER UNDIFFERENTIATED w

“INDHYAN - SOURCE ROCb . DIAMICTITE

UPPER . PROTEROZOIC

Fig. 3. Stratigraphic zonations of central-southern Nepal. Ramkot Fm. Pink to grey sandstone and purple to grey fauna. The formation has a few intervals that contain up to shale 850 m thick; 10% TOC and is considered an important potential source Gawar Fm. Limestone and dolomite with abundant stro- rock. The Taltung Formation disconformably overlies this matolites and algal mats and becomes more shaly and sandy Sinse and is comprised of conglomerate sandstone shale. upwards; reaches a maximum thickness of 1700 m and is Gondwana sediments are considered an exploration objec- considered an exploration objective; tive in Nepal. They probably occur in small pockets beneath Khara Fm. Dark grey, microcrystalline limestone and the base Siwaliks (Figures 8, 9) in the eastern Nepal Terai, shale; possibly in the Gandak depression in the Birganj and Katwa Fm. Dark grey to black shales with minor stroma- Lumbini areas and could be caught up in smaller thrust slabs tolitic dolomite; a potential source rock; beneath the Siwalik Fold Belt and main boundary thrusts. Am Fm. Dense dolomite with lesser amounts of sandstone Good reservoir rocks were not seen in outcrop hut several and shale; restricted to south-central part of Nepal; a poten- organically rich intervals have been mapped. The lower coal- tial subcrop reservoir. hearing Gondwana could be both a source and reservoir for Gondwana Group (Late Carboniferous to Early gas and the marine Upper Gondwana may be a potential oil Cretaceous) ~ The Gondwana is a group of rocks occurring source rock. in basins on the lndian Craton (unconformably below the Surkhet Group (Late Cretaceous to Early Miocene) - The base of the Siwalik Group of the Terai) and in the southern Surkhet Group occurs in the southern, central and western part thrust sheets of the Lesser Himal. The thickness of the Group of the Lesser Himal where it unconformably overlies in eastern and central Nepal, which is quite variable, is Lakharpata or Gondwana rocks. The Group attains a maximum approximately 1000 m in the ridges immediately above the thickness of 1200 m and is separated into the Melpani, Swat MBT in central Nepal and is interpreted from seismic analy- and Suntar Formations (Sakai, 1983). The Group is correlated sis to be at least that thick in the basins of the Terai (Bashyal, with the oil and gas producing formations of the Assam and 1980; Sakai, 1985; Datta et al., 1983). The Group is sepa- Potwar basins (Rangarao, 1983) and with the “Unnamed rated into two formations. The Sisne Formation uncon- Formation” of Northern India (Schroeder, 1981) sediments. formably overlies the L&harp& Group and is composed of The Swat Formation is composed mainly of shale that diamictite and shale and contains late Paleozoic marine contains intervals with greater than 2% TOC and some of the

CEG 106 DIsElnkr lYY4 Mrlpani organic shnlcs have 20%, TOC. In the Danp Valley, southern Nepal. Seismic control in eastern Nepal is quits the porosity of a distinct Melpani sandslonc is filled with dense (appnximatcly 2 km x 4 km). This xca is character- solid hydrocarbon Wind, IYY~J. ired by many bassment~contn,llcd structures offsettin@ srdi- Siwdik GIW[I (Late Miocene to Pliocene) ~ The Siwalik ment-filled suhbasins and erabcns beneath the Siwalik Group is a thick section of fresh-water molasse. sxposcd in a molasse. The grid (IO km x IS km) of rcconnaissancc s&s- ssties of fault slices that make up the Siwalik Fold Belt and lit mic lines covering the halance of the Terai has identified beneath the alluvial deposits of the Tcrai (Delcaillau, 19x6). se~cral gculogical settines which hnvc the potential for The Group is up to 4500 m thick and is scpxated into three f& hydnxarhon pnxpccts. Thcsc include structured traps rclatcd mntions: Lower Siwalik (LS), Middle Siwalik (MS1 and MS2) and Upper Siwalik (US). The lower part of the Group i\ con- to normal faulting involving prc-Siwalik formations and posed of fine-grained sandstones containing shale intcl-vals (IS thrusting involving the Siwaliks (Fi@w 4): subcrop traps and MS I ) and becomes cot~rsfr @nrd upwards (MS2 and involving pre-Siwalik sequcnccs (Figure 51: and structural US). Petroleum ohjcctives are expected to he restricted Iu the trap\ associated with blind ti~lds in front of the Siwalik Fold lower part of the Group where thcrc is an effective combination Belt (Figures 6. 7). The location\ of seismic lines show11 in of potential sandstone rcscr~oirs and shale se&s. Fipures 4. 5 and 6 are shown on Figure 8. The hasc Siwdik seismic marker (Figures 4, 5, 6) is an 7.0 GEoPHYStCs important reflection in the Tel-ai region. It rcprcsents an Geophysical exploration methods, rcflcction seismic. oncunlbunity that separates the Siwaliks (mid-Miwxnc and jiravitv and magnctics, combined with surface mapping and younger) fri~nt older strata (L~wel- Miucenc to Precambrian). hasin analysis. have cstahlished the subsurlhcc fmmewo~-k uf Figum 8 and Y reprcxnt structural maps of this marker in

N

F ig. 4. Migrated Line 59 in eastern Terai. showing two stages of thrusting (see Figure 8 for location) (‘1i, i 107 ,kr,l,,rr, ,,,I,

“,R. FRIEDBNREICH. 0.L SI.,ND. I,.M.S. PKADHAN and R.B. SHKCSTHA

TERAI SIWALIK FOLD BELT ” LESSER HIMAL

SCALE: H = V 10km

Fig. 7. Structure cross-section along tine 31. the eastern and western Terai, respectively. The unconfor- seeps is interpreted to c”me from a conventional s”urce rock mity lies between 3500 and 4600 m below the Terai plain beneath the nappes and rocks with source potential have been which is approximately 100 m above sea level (al.). There is sampled from the Lakhqaw, Gondwana and Surkhrt Groups. no dominant east-west gradient to the base Siwalik marker; Thermal modelling suggests that potential source rocks in the however, the dipping of the marker toward the Siwalik Fold prospective part of Nepal are in the marginally mature-f”l--oil Belt is very apparent. t” late-in-the-gas generation window. Nine seismic and gravity traverses cross the Siwalik Fold Belt and identify major folds and thrust faults that may con- 9.0 R~sliwom tain substantial thicknesses of potentially prospective pre- Siwalik rocks. Line 89 (Figures 9, IO) cr”sses a large Siwalik Studies of outcrop samples and analysts of Shell fold and demonstrates good reflections on the flanks of the Biratnagar I indicate that effective reservoirs and seals are structure but there is no coherent date in the core. Gravity likely to be found in the Lower Siwalik, Surkhet and measurements along this line show a substantial 25 mgal Gondwana sandstones and shales. Outcrop studies have not anomaly above regional f”r the traverse. Model studies show identified large areas of carbonate reservoir development in (using densities derived by methods described by Gardner et the Lakharpata/Vindhyan Group, although it is expected that al., 1974) that the anomaly is caused by highier) density rocks the unconformity at the base of the Siwalik molarsc will pro- being involved in the core of the structure. These model den- vide a large number of attractive carbonate as well as cl&c sities are comparable with those of the prospective pre- exploration objectives. Siwalik (Lakharpata) dolomite (Figures I I, 12). From the above, it is apparent that the gravity method may 10.0 DRILIJNG be very beneficial and cost-effective in c”ncert with seismic Nepal is virtually unexplored. The country’s only well was surveys in delineating hydrocarbon prospects in the southern drilled on a seismically defined, basement-controlled put of Nepal. anomaly in the far eastern part of the country near Biratnagar. The well was abandoned at 3530 m after pene- 8.0 GEocHEMtsTtw trating 3143 m of typical Siwalik molnsse and 387 m of A considerable amount of geochemical work has now been arkose and shale that was interpreted to be of Eocene or completed on rocks from Nepal. The oil from the Dailekh younger age. No hydrocarbons were reawered, although

C)H(; 110 Derrnlh.,~,w* PCTROLF,UM clxxocY or NEPA,

a LESSERHIMAL SEaJENCES 1 m SWAM FOLDBELT ii 28N m SiWALlK MOLASSE Con,o”is in m bsi

!7N

0 50 km

Line 59: See Figure 4 Line 52: See Figure 5 Line 31: See Figures 6 & 7

83E 84E 85E 86E 87E

Fig. 8. Eastern Terai. structure map 01 Base Siwalik unconformity and location of Lines 31, 52 and 59, small amounts of background (mud) gas were encountered in Compagnir GenCriilr de Geophysiqur (CCC). 19x0, Fin>,, report airborne rnagnetomcter survey Nepal: Unpubl. Rep. for the Nepal Dept. of Miner the lower part of the Middle Siwalik. and Geulogy. 91p. “nlld, N.R.. Milru, ND. and “undyopndhyay. 19x3. KeCem trends in the 11.0 OPPOHTUNITIW study 01 Gondwaoa hasins of Peninrula and extra-Peninsuliir IwJia: Femlrum Ahi2 Journal, Exploration opportunities in the Terai consist of structures Uelcaillau, B.. 14Rh. Dynanlique et e”“l”ti”n morph”.structurale d” piemont associutcd with blind thrusts, bascmcnt-controlled structures, frwml de I‘Himalaya: ies Siwaliks du Ncpvl oriental: R&w dc Ciulugiu stratigraphic pinch-outs and subcrop traps. Major folds and Dynamiquc a de GCographic Phyriquc. Paris. 27. Fast. 5, 3 19~337. thrusts in the Siwalik Fold Belt are likely to provide strut- Ehner. E.J.. IVXO, Grwity survey. acquisition, pmcc*sing and intrrprclalion mport. Terai and Siwalik Fold Hclt, Kingdom of Nepal: ELS Consulting. turally controlled traps containing Lakharpata to Siwalik Oct. ,9x’). reservoirs. Drilling depths to objectives are from 3500 to Frank. W. and Fuchs. G.R.. 1970. Geological investigations in West Nepai 5000 mctrcs in the Tcrai and from 2500 to 4000 metres in and their signilicancr Cur Ihr geology oi Ihr Himdayas: Geolugische the Siwelik Fold Belt. I

(IK 111 I>rwlilhrr i’l’,.l 81E 82E 83E 84E

m LESSER HIMAL SEQUENCES 29N. 1 2222x,, m SiWALlK FOLO BELT j: SWAM MCILASSE Contours I” mlt’s,

Lx 896s Figures 10, 11 & 12

8iE 82E 83E 84E

Fig. 9. Western Terai, structure map of Base Siwalik unconformity and location of Line 89 (Siwalik Fold Belt traverse)

Mitchell. A.H.C.. 197’).G”idCS 10 nmai pro,,inces in the Central Himalaya Sltkklin. 1.. 1980. Geology of Nrpal and ttr rcgmn:~lIriimr: J. Geol. Sot. Coili5ion Reli: ,hc Ya,“r “i rrgionai stratigiaphic C”rrelati”ni and ,cc,ollic Lmdon 137. 1-34. anidogics:Gcdogiual Society of China. Mcm. 3. 167~(94. Windlcy. R.F.. 19x3. hlem,>qJhism nnd teCtOlliC1of ttlc Himalaya: J. Cd Parka\h. 8.. Shama R.P. and Roy. A.K., IW,, The Siwalik GW”,, sot. hndon 140, 84%X05. ~rdaire, iediments shed hy colli\ion ur conlincnlal plate*: Sedillient. Gml. 25, 127-15’). Raivrrman. V,. Kuntr, S.V. and Mukhcrjca, A.. 1’183.Basin geometry. REFEKENCESFOK GENERAL READWC Ccnwoic redi,,,snrutio,~ anil hydrucarhon pmspccts ill Nor,h wes,er,, Dspnrtmentof Mines and~;cology Nepill CDMGh IWi, Nepal:exploration Himlayu and lndo-Cia”gcric Rein,: Pclrolcum Asia humal 6. no. 4. h,- oppurtuniries:Bmchurc. 42. ~, 1990.Exploration opportunih in Nepal:Bmchure. Riing*rm. A.. 14x3. Geology an* hydrucarh”” pdcnlial Of>/pan of Assam- Ankan Basin and its adjwcm rcgim. in Pelloliirruui basins of India: ~( 19w.The King&,“7 <>l Nepal. expl”rati”” opponunities. Brochure. Prtroleum Ah Juumal 6. 127-158. Ganrser..!.. 1%9.Geology o/the Himulayas: Wiley Inlcrscicncc. Lundon. S&i. H.. IUS5 Gedogy of the Kali Gandaki Sup Group: Mm kc. Sci.. NewYwk. Kyushu Clniv.,Ser. 13.C;col.. WI. XXV. nu. 3.137-397. Karunilkaran.C.;and Rm A.R..IWh. Slatu, UI cxpluraiion hi hydmcarbon Schrocdcr.J.W., 1’181,A rrpun 0” petrolmm cxploralion “1 Nepal: Unpubl. in lhc Himalayxregion contributions lo rlratigraphyimd slru~tw~: Rep. Ibr ,hc Nepd Dspartment nf Miner and Gculugy. 74p. HimalayanGculugy Seminar. Sec. 111, New Delhi. Mis Puhl.Gcol. Sure. S,,rcs,,,;,. S.8. and Shrerthn. J.K. 1’)83. The gr”lugical cnap of westem Ilidiil,IW’). 41 (5) Mh. Crnlral Nepal: His Majesty.\ Guvclnmral. Ministry of Industry. Moinar.P. ilndTupponnier. I’,. 1477.‘The collthion hcluccn Indiii and Depsrlmcnl d Mines and Geology. Lnmcbour, Kathmundu. Curasi;i:Scientific American236. no 4.2W I Shd. O.L.. 1w3, Nqxll. sourceand Xii\ Wd\. hydri,carh

c,,:ci 112 “rcc>l>hcrWil

O.K. FKIEIxaKEICII. O,L, SLlNLl LI.M.S. WADHAN :ind K.B. SHKESTHA

SW NE LVMBlNl PLAiN SOMESHWAR RAPTI “ALLEY MAHABHARAT RANGE (ES,) LEKH

LEGEND

PLEiSTOCENERECENT ChRBONlFEROUS TO LOWER CAETACEO”S MIOCENE PLIOCENE SCALE: H =” GD GONDWANA GP su “PER SIWN.lK 0 5 k”, A THRUSTFAULTS SM MlDDLESIWRUK SL LOWERSIWMK PRECAMBRIAN 70 G G SEISMICMARKERS PAEOLOIC X CRETACtOUS MlOCENE “IN “INOHYAN GP x SEiSMlCREFLECT LK LAKHARPATA GP SURKHET GROUP SN SUNTAR MB1 MAIN BOUNDARY THRUST SW SWAT MFT, MAIN FHON~reL lHHUST

Fig. 11. Structure cross-section along Line 89.

OBSERVED GRAVITY c 720 CALCULATED GRAVITY 3 .-g E 710 x > 9 a 700

690 0 5 10 15 20 25 km

0 F r 2 f $ 4 0 6

0 5 10 15 20 25 30 SCALE H=V km

Fig. 12. Model study for Line 89 (Siwalik Fold Belt traverse).

(lMi 114 “UCC,l’k,~,‘,‘W