Sedimentology, petrography and tectonic significance of the shelf, flysch and molasse clastic deposits across the Indus Suture Zone, Ladakh, NW India

Sedimentary Geology, 40 (1984) 249-286

249

Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

S E D I M E N T O L O G Y , P E T R O G R A P H Y A N D T E C T O N I C SIGNIFICANCE OF T H E SHELF, FLYSCH A N D M O L A S S E CLASTIC D E P O S I T S A C R O S S THE I N D U S S U T U R E ZONE, LADAKH, N W INDIA

M.E. BROOKFIELD and C.P. ANDREWS-SPEED *

Department of Land Resource Science, Guelph University, Guelph, Ont. NIG 2W1 (Canada) Minex, P.O. Box 30090, Lusaka (Zambia) (Received January 3, 1983; revised and accepted January 3, 1984)

ABSTRACT Brookfield, M.E. and Andrews-Speed, C.P., 1984. Sedimentology, petrography and tectonic significance of the shelf, flysch and molasse clastic deposits across the Indus Suture Zone, Lodakh, NW India. Sediment. Geol., 40: 249-286. In the Ladakh area of India, a passive Triassic to Lower Cretaceous continental margin is indicated by Indian-shield-derived clastics on the shelf and Atlantic-type turbidites off the continental margin. Mid-Cretaceous initiation of ocean closing is reflected in Pacific-type flysch and associated island arc volcanics, which were initially emplaced over the northern Indian continental margin in late Cretaceous times--resulting in the formation of a fore-deep in which flysch and minor continental molasse accumulated briefly during the late Cretaceous. These transient uplifts were, however, rapidly destroyed for by the latest Cretaceous to latest Palaeocene, uniform carbonate sediments were being laid down over the area. With the early Eocene, the development of a second fore-deep, this time filled with very thick flysch and molasse sediment, indicates a major uplift of the northern Indian margin, which we attribute to the development of an Andean-type magmatic arc on the northern edge of the Indian plate. Uplift and molasse sedimentation in this fore-deep continued through the Oligocene and Miocene, when the collision of India and Asia caused extensive deformation of all the sequences and the shift of molasse sedimentation southwards to the Himalaya foothills and Indo-Gangetic plain.

INTRODUCTION

The Indus Sutue Zone marks the collision between India and Asia which took place during the Tertiary (Fig. 1). As in other mountain belts, the timing and nature of deformation can partly be worked out by analysing the clastic sequences which were shed off the Indian and Asian margins during their history. Unfortunately, for many years there have been confused and contradictory interpretations of the * Present address: BP Petroleum Development (UK) Ltd., Farburn Industrial Estate, Dyce, Aberdeen AB2 0PB, Scotland.

0037-0738/84/$03.00

© 1984 Elsevier Science Publishers B.V.

250 Mesozoic-Tertiary clastic units of the Indus Suture Zone. Much of this confusion is due to the application of the Swiss terms "flysch" and "molasse" to these units. We intend to describe the main clastic units of the Indus Suture Zone, infer their depositional environment and tectonic significance, and comment on the application of the terms "flysch" and "molasse". We contend that these terms are quite reasonable when used to characterize thick sequences and are particularly useful in the Indus Suture Zone, because the clastics have close analogies both in depositional environment and tectonic setting to the Swiss sequences.

Concept of flysch and molasse The term "Flysch" (capital letter) was introduced by Studer in 1827 to describe a formation of dark grey shales and intercalated sandstones which overlies an Upper Jurassic formation: it means " a shaly rock" (HsiL 1970). The general term "flysch" (small letter) has gradually come to be used for thick sequences of re-deposited deep-water clastics (Rupke, 1978); a use we accept and recommend here. "Flysch" (capital letter) should be restricted to such sequences in the Alps (HsiL 1970) of Cretaceous-Tertiary age (cf. Matter et al., 1980). In Switzerland, "Molasse" (capital letter) consists of terrigenous clastic formations derived from the rising Alps during the Tertiary: it is thus a lithostratigraphic term of presumably supergroup rank (Triampy, 1980). Environments represented are alluvial fans, gently sloping flood-plains with meandering and braided rivers, lakes and swamps; marine to brackish water environments of current-swept seas, paralic deltas and tidal flats. The general term "molasse" has been used in a lithological sense for thick successions of sandstones and conglomerates. Mitchell and Reading (1978) applied the term "molasse" to any thick succession of continental deposits consisting in part of sandstone and conglomerate which are formed as a result of mountain building. However, this definition leaves out the deltaic and shallow marine units found in the Swiss "Molasse". Though Matter et al. (1980) carefully left "molasse" undefined, we take it here to refer to thick post-orogenic successorbasin or foreland-basin continental to shallow marine clastics, sometimes with deep-water "flyschoid" turbidite units. Both terms "flysch" and "molasse" are very useful in characterizing the overall tectonic environment and overall sedimentary regime. We further distinguish Atlantic-type flysch, characteristic of passive continental margins, from Pacific-type flysch typical of subduction-related settings (Mitchell and Reading, 1978). "Oceanic" (or pre-flysch) refers to thin sequences of deep-water limestones, cherts and clays, often associated with ophiolites.

Petrographic methods and concepts Apart from field counts of pebbles, we collected mostly the coarsest sandstones possible, since these give representative grain compositions for petrographic analysis

25l and the grains can readily be identified in thin section. During transport, mechanically strong grains are enriched at the expense of rock fragments and felspar. Thus finer-grained sandstones tend to be texturally more mature than coarser grained ones (Odum et al., 1976). Unfortunately some sedimentary units, particularly the flysch units, have marked effect on the proportion of lithic grains when comparing conglomerates with interbedded sandstones. On the ternary grain composition diagrams, since we are primarily interested in maturity, Q on the QFL diagram includes both monocrystalline and polycrystalline silica, dominantly quartz. L includes limestone as well an unstable rock fragments. We include such rocks as micaceous quartzite in the L per cent, since these are readily broken down to separate quartz grains. We have used the petrographic provenance concepts of Dickinson and Suczek (1979) in order to interpret the tectonic environment in which the sediments were deposited.

Tectonic setting The Indus Suture Zone, which lies north of the High Himalaya, has been widely recognized as being the site of an ocean which separated the Indian continent from Asia in pre-Tertiary times (Gansser, 1977, 1980). Only in the northwestern area of Pakistan and India are the suture zones and continental margins on either side exposed outside China and Tibet. In the Ladakh area, clastics associated with both the opening and closing stages are exposed (Fig. 1). We distinguish three major tectonic divisions in this area: the Tethyan Zone (the northern margin of the Indian continent), the magmatic arc and suture zones of the Indus-Tsangpo suture (divided into the Indus Zone, the Ladakh Batholith Zone and the Shyok Zone), and the southern margin of the Asian continent with its marginal Upper Tertiary magmatic a r c - - t h e Karakorum mountains. In this paper we concentrate on the clastic units of the Tethyan Zone, and of the Indus and Ladakh Batholith Zones. From south ~o north, these units and their clastic deposits are as follows (Table I): (1) The Tethyan Zone, with an autochthonous shelf sequence including: the Guimal sandstone (Lower Cretaceous), Kangi La flysch (Upper Cretaceous), Upper Maastrichtian quartz arenites, and ?Basal Eocene clastics. (2) The Indus Zone, consisting of several thrust sheets: (a) The Lamayuru unit, containing the Lamayuru flysch (Triassic-Jurassic); (b) The Dras unit, with the Dras Volcanics and Nindam flysch (Cretaceous); (c) The Khalsi unit, with the Khalsi limestone overlain by the Khalsi flysch (Cretaceous); (d) The Miru unit, consisting of an early Tertiary (?Palaeocene to Eocene) shelf, flysch and molasse clastic sequence--the Basal clastics, Jurutze marls, Jurutze flysch, Stok Kangri molasse and Kongmaru La molasse--which is unconformably overlain

252 by a very thick late Tertiary (?Oligocene to Miocene) m o l a s s e - - t h e Rumbok, Zinchon, N i m u and H e m i s molasse. (3) The Ladakh Batholith Zone, with a u t o c h t h o n o u s molasse, the Upshi molasse and W a k k a Chu molasse. The relationships of these units are shown on the cross-sections of Fig. 2. We think that the allochthonous Triassic to Cretaceous flysch of the Indus Zone was derived from b e y o n d the northern edge of the Indian shield by late Cretaceous to early Tertiary thrusting and that these thrust sheets were at least partially emplaced

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prior to the intrusion

of the Ladakh

elsewhere (Andrews-Speed

batholith.

and Brookfield,

Justification

f o r t h i s v i e w is p r e s e n t e d

1982).

TETHYAN ZONE North

of

Cambrian mainly

the

crystalline

to Eocene

axis

sedimentary

of the

Himalaya,

this

rocks has no major

consists of shales, carbonates

and quartzites

fossiliferous

angular

deposited

sequence

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on an intermittently

TABLE I Formations distinguished and their possible or probable age Age

Tethyan zone

Indus zone

Miocene . . . .

? .

Ladakh batholith

Nimu Grits .

.

.

.

.

.

.

.

.

? . . . . . .

Wakka Chumolasse *

Zinchon molasse . . . . . .

.9 .

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

Hemis conglomerate * R u m b o k molasse

Oligocene

Kongmaru La Red molasse Stok Kangri Conglomerate Eocene Jurutze flysch * Jurutze marls Basal clastics

Basal ?Eocene clastics Carbonates * Palaeocene Carbonates * Upper Cretaceous

Kangi La flysch * Chikkim limestone * Guimal sandstone *

Lower Cretaceous

.

.

.

.

.

.

.

.

.

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.

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.

.

?...........

Dras volcanics * .

.

.

? .

.

.

.

.

.

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Nindam flysch . . . . . .

Jurassic

.

...........

? . . . . . .

Spiti shale

.....

Mainly carbonates and quartzites *

Lamayuru flysch *

Triassic * Some fossil control on age.

?.....

.

.

.

.

.

.

.

.

of and

.......

Upshi molasse

255

subsiding continental shelf (Gansser, 1964). Near Rangdum, on the southern edge of the Zanskar range (Fig. 1), six predominantly sandy units of Mesozoic and Cenozoic age have been noted. The four Cretaceous to Palaeogene clastic units are of greatest interest for any regional interpretation and are described below (Fig. 3).

? Eocene clastics

v a r i c o l o u r e d fine-gr. sandstones & siltstones. late Maastrichtian to

Limestone and marl

Palaeocene

Quartz-aren ite

Limestone and

limestone & marl

late

very mature qtz-areni te

Upper Maastrlchtian

very fossiliferous limestone & marl

marl

?Campanian to Kangi La Lower

flysch

Fine-grained graded calcareous sandstones and calcareous shales and silty sha!es.

Maastrichtian

Chikkim limestone

Turonian Santonian ...........

Guimal

Lower

sandstone

Cretaceous

Spitl shale 'Upper Dogger'

Middle-Upper Jurassic

Black, silty shale. Calcareous ssts and shale.

Upper Triassic oTd-Jurassic

Thickly bedded

T 100 m.

1

f

Thickly bedded dense & nodular limestone.

Kioto limestone -

Fine to coarse grained quartzose sandstones (arkosic wackes) with shale interbeds towards the top.

limestone.

Fig. 3. Mesozoic to Cenozoic stratigraphic section of Tethyan zone at Rangdum (from Fuchs, 1979; Gaetani et al., 1980; and authors' observations).

256

Guimal sandstones

The Guimal sandstones outcrop in many parts of the Tethyan Himalya; Fuchs (1979) assigned 250 m of sandstone and shale north of Rangdum to this unit. In the upper part of the unit, dark shale is interbedded with sandstone, which is generally fine and medium grained and in beds less than 50 cm thick. The sandstone beds are ungraded; the only clearly visible structure we saw is sporadic parallel lamination throughout many beds. Lower down in the unit, the proportion of sandstone increases as does the thickness of individual beds which reaches 1.0-1.5 m. The felspar is dominantly potassium felspar which includes both perthitic and cross-hatched twinned varieties. The quartz grains show considerably undulosity and strain lamellae; but this reflects deformation and not source terrain, as shown by the well-developed mortar texture and preferred orientation of many of the grains. The Q F L plot for the Guimal sandstones (Fig. 4) indicates a continental source terrane. The presence of glauconite and phosphate suggest a shallow marine environment. The poor sorting indicates that the sandstones were not deposited in a high-energy coastal zone where winnowing would have resulted in a high degree of maturity (Johnson, 1978).

O Guimat sandstone (8)

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L

GUIMAL S S T . Qp/Q P/F LslL LvlL Matrix

0.1 0.2 0 0.5? detrital 15-40%

(~,\

\

P

KANGI LA FLYSCH 0 0 1.0 0 detrital 10-30%

/

/

? EOCENE SANDSTONES 0.2-0.5 0,1-0,3 1,0 0 detrital 20-40%

Fig. 4. P e t r o g r a p h y of Mesozoic to Cenozoic clastic units of T e t h y a n Zone. Q = total quartz; Qp = p o l y c r y s t a l l i n e quartz; Q,,, = m o n o c r y s t a l l i n e quartz; F = total felspar; P = plagioclase felspar; K = p o t a s s i u m felspar; L = total lithic g r a i n s (including limestone); L s = s e d i m e n t a r y lithic grains; L,. = v o l c a n i c lithic grains.

257 Kangi La flysch This unit consists of about 400 m of thinly bedded, calcareous, graded and bioturbated, very fine-grained sandstones, alternating with bluish, silty, calcareous shales (Fuchs, 1979). Gaetani et al. (1983) recorded probably Upper Campanian foraminifera and ammonites from near the top. In the Rangdum-Kangi La section, the sandstones become thicker bedded and coarser grained upwards, though remaining fine grained. The individual sandstone beds are graded, generally about 5 cm thick at the base of the section, thickening up to 0.5 1.0 m at the top. Apart from parallel lamination and heavy small-scale bioturbation, there are no sedimentary structures present. Some graded beds have concentrations of small fossils at their bases, only crinoid stems being so far determinable. These sediments would be classified as distal turbidites of Facies D (Walker and Mutti, 1973), but their heavy bioturbation and stratigraphic position between deep shelf (Chikkim limestone) and shallow shelf (Maastrichtian limestones) deposits indicate a shelf environment. They closely resemble shelf storm deposits (Kreisa, 1981). Samples collected from base to top of the section are all mature lithic greywackes, containing only traces of felspar but abundant small limestone grains (Fig. 4). The abundance of carbonate grains and the rarity of felspar, igneous and metamorphic grains suggest a source from exposed limestone terrain. Petrographically the Kangi La flysch most closely resembles sediments of foreland uplift provenance (Dickinson and Suczek, 1979) and in particular what they considered the most characteristic rocks of this provenance--rocks with moderately high quartz contents, strikingly low felspar content, and often high proportions of recycled detrital carbonate grains from exposed limestone. Upper Maastrichtian arenites This arenite, 10 m thick unit, extends over 100 km 2 with a constant thickness and was interpreted by Gaetani et al. (1980) to be a shoal complex. Our two samples (kindly supplied by M. Gaetani), consist of fine to medium grained, well-sorted quartzites, with recrystallized sericitic matrices. The grains are almost entirely strained quartz, but the rocks are overcompacted, with metamorphic grain boundaries, and thus the straining is secondary like the Guimal Sandstones. Nevertheless, abundant zircon and tourmaline indicate an igneous rather than a metamorphic source. ?Basal Eocene clastics Overlying the Upper Maastrichtian to late Palaeocene carbonates is a thick unit of red, green and grey, alternating fine-grained sandstones, siltstones and shales,

258

reminiscent of the basal Eocene clastics of Rumbok, to the east (p. 269). The sandstones consist of finely festoon cross-laminated and parallel-laminated fine-grained, well-sorted lithic arenites and greywackes, with angular to sub-angular grains. Limestone grains are very abundant, between 10 and 55%. Potassium felspar varies between 13 and 25% of the grains and greatly exceeds plagioclase (Fig. 4). Chert is much more abundant than in the previous two units analysed and varies between 5 and 20% of the grains: in addition, there are traces of clinopyroxene, spilite, kyanite gneiss, zircon and sphene. The matrix is a sericite-replaced detrital one, consisting dominantly of poorly sorted phyllosilicates. All this suggests a source richer in metamorphic and igneous rocks than that of the Kangi La flysch, which these ?basal Eocene clastics otherwise resemble. On Dickinson and Suczek's (1979) plots, the ?basal Eocene sandstones most closely resemble their "recycled orogen provenance with mixed contributions from foreland uplifts and collision orogen units." The abundance of chert may suggest a significant contribution from melange terrains, such as those associated with the Indus Zone to the north. Nevertheless, the low plagioclase/total felspar ratio is more typical of uplifted basement. The source of the ?basal Eocene sandstones is thus enigmatic, but appears to have included a sedimentary foreland uplift, collision orogen units (maybe melange) and uplifted basement.

Interpretation The Guimal sandstones represent the first major coarse clastic influx into the Tethyan Himalaya during the Mesozoic. The Upper Triassic and Middle Jurassic sandy units are much thinner, 70-80 m and 7-10 m thick, respectively, in Zanskar (Fuchs, 1979). Unlike the Guimal sandstone, these units are very mature quartz arenites, with almost no unstable minerals, and are typical of shallow shelf environments with extensive reworking; the Triassic sandstones are in fact white orthoquartzites. In the Lower Cretaceous to ?basal Eocene section north of Rangdum clastic rocks dominate the section. None of these are typical turbidites; the evidence collected so far indicates that they are all shelf sediments. Nevertheless, there is indication of a change in source terrance between the Guimal sandstones and the Kangi La flysch. Although critical evidence has been overprinted, the petrography of the Guimal sandstones suggests a continental granitoid or possibly high-grade metamorphic source. In contrast, the Kangi La flysch and ?basal Eocene clastics have petrographies more characteristic of foreland uplifts and collision orogen units. In view of the proposed late Cretaceous-Eocene emplacement of the Indus zone ophiolitic melanges (Brookfield and Reynolds, 1981; Searle, 1983), and the evidence for foreland uplifts in Pakistan to the west (Wells, 1983), it seems reasonable to consider the Kangi La flysch and ?basal Eocene

259

sandstones as having been deposited in a fore-deep, lying between the Indian shelf and the foreland uplifts and melanges to the north. INDUS ZONE

This complex zone lies between the Tethyan sequence to the south and the Ladakh batholith to the north. There appear to be four major tectonic units separated by major faults. Due to the lack of detailed work in the Ladakh area, the relationship of these tectonic units is not precisely known. Our observations lead to the interpretation of Fig. 2, in which the Dras and Lamayuru units lie tectonically above the Khalsi and Miru units. We studied these units in two main areas: between Lamayuru and Nurla, and between Leh and the Markha valley (Fig. 1).

Lamayuru unit This unit is named after the monastery of Lamayuru, between Leh and Kargil, and is mostly composed of flysch called the Lamayuru flysch. Frank et al. (1977) separated a Lamayuru and a Namika La flysch, but we do not consider these sufficiently distinct to warrant two names; furthermore they are of the same Triassic-Jurassic age (Sterne, 1979; Brookfield and Westermann, 1982).

Lamayuru flysch Near Lamayuru and on the northern edge of the Spongtang Klippe, this flysch consists of calcareous and non-calcareous shale alternating with thinly bedded fine-grained, frequently graded sandstones. Also present are thin limestones, large exotic blocks of Triassic to Jurassic limestone (Bassoullet et al., 1978b, 1981, 1983) and serpentinite breccia and m61ange (Fig. 5). Although the flysch is variable, the sandstone beds are rarely thicker than 5 cm. They contain various combinations of incomplete b - e and c - e Bouma sequences (Fig. 6). Most of the Lamayuru flysch is a distal turbidite facies D sequence (Walker and Mutti, 1973), which is interpreted as having been deposited on a basin plain (Mutti, 1977). The frequency of light coloured calcareous shales may indicate a hemipelagic origin. On the QFL plot (Fig. 7), all these sandstones lie in the field of continental block provenance (Dickinson and Suczek, 1979), and other aspects of their petrography are consistent with this. However, the fine-grained nature of the sandstones makes this conclusion tentative. The abundance of calcite in both the sandstones and shales indicate a carbonate-rich depositional environment. The sandstones from the Spongtang Klippe are similar in grain size and texture, but compositionally are quartz wackes (Fig. 7). Nearly the whole matrix is calcite, much of which may be recrystallized from detrital carbonate grains.

260

8

North

Lamayuru~

15 14

l~~~South

~

~Ik~ ~ I L ~ I ~ ~X," T~To~YEAN

13

about I Kin. L

|

Arrowsshowway-up of beds.

Fig. 5. Field sketch of Lamayuru flysch units south of Lamayuru. I = Highly sheared shale and thin fine-grained sandstones: 100 m; 2 = ophiolitic melange: large blocks of serpentinized hartzburgite in a serpentinite breccia: about 100 m; 3 = alternating fine-grained sandstone and shale: 800 m: 4 = serpentinite breccia: 10 m; 5 = thinly bedded grey-black fissile shale with carbonate concretions, passing north into thinly bedded fine-grained sandstone and shale: highly contorted: 2000 m; 6 = black fissile shale alternating with thin calcareous micaceous fine grained sandstone: very badly shattered and folded to the north: 500 m; 7 = very shattered limestone and shale: poorly exposed; 8 = large limestone exotic, of Upper Triassic and mid-Jurassic age (Bassou]]et et al., 1981 ); 9 = thinly bedded sandstone and shale; calcareous: 2500 m; 10 = fissile shale: 400 m; Jl = thickly bedded sandstones and shales passing down into thinly bedded sandstone and shale: ?g00 m; 12 = fissile papery shale: 300 m; 13 = Alternating thinly bedded fine-grained sandstone and shale: 71000 m (this is type Lamayuru flysch of Frank et al., 1977, with Upper Triassic bivalves): 14 = thinly bedded sandstones, alternating with thick grey-black shale: ?m; 1.5 = ophiolitic melange: contact with Dras unit.

The difference in composition between these two sets of sandstones is probably not significant and may indicate that they were at different stratigraphic levels within the Lamayuru flysch. Thus, the Lamayuru flysch was deposited along a passive continental margin. The turbidites were deposited on a basin plain and also possibly on the outer part of a deep-sea fan. The exotic blocks of limestone are interpreted as olistoliths which have slid northwards off the Tethyan carbonate shelf and have been tectonically incorporated within the flysch during both deposition and emplacement (Bassoullet et al., 1983). In gross composition, the Lamayuru flysch resembles the Ayios Photos Group of Cyprus, which has been interpreted as having been deposited on a late Triassic to early Jurassic passive continental margin (Robertson and Woodcock, 1979). Dras unit

This unit is named after the village of Dras in western Ladakh (Fig. 1). It includes rocks which have been referred to as the Dras volcanics (Frank et al., 1977), the Nindam unit (Bassoullet et al., 1978a), and the Dras flysch (Fuchs, 1977, 1979). We simply use the term Dras volcanics for the predominantly volcanic part of the unit, mostly confined to the western part of Ladak, and the term Nindam flysch for the mostly volcaniclastic flysch section which occurs in the eastern areas.

261

Fig. 6. Lamayuru flysch, below Prinkiti La, about 3 km south of Lamayuru. Thickest bed is 5 cm thick. Q

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01.0 9 (mean 07) 10 05 05 detrital 2540~ An25 49

Fig. 7. Petrography of Indus zone flysch units. Legend as for Fig. 4.

KHALSI FLYSCH Khals,.Nurla Shingo 0 10 10 detrlta13050% An25-35

0 10 05 05 detrdaJ 50.70% An30 35

262 I

i

Southwest

Northeast

ta.~yuru

,~

DRAS UNIT

(Nindam f I y s c h )

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MIRU

MELANGE

UN1T

UNI T

Fig. 8. Section along the Yapole gorge between Lamayuru and the Indus river. 14 = Lamayuru flysch;

= ophiolitic melange: chert, flysch, serpentinite in serpentinite matrix. Nindam flysch. 16 = Greenish, purplish and greyish graded volcaniclastic sandstones, siltstones and shales: occasional coarse tufts, and green aphanitic lavas; 17 = thinly laminated green, purple, lilac and red graded porcellaneous tuffaceous siltstone and argillites: becoming thicker and coarser to the south; 18 = thinly bedded graded fine-grained felspathic sandstones (5-20 cm thick) alternating with thin grey-black shales and containing several exotic limestone blocks; passing southwards into thicker bedded graded felspathic sandstones up to 2 m thick. Ophiolitic melange. 19 = Sheared serpentinite; 20 = aphanitic volcanics (?Dras volcanics); 21 = ophiolitic melange. Khalsi unit. 22 ~ Highly sheared interleaved fine-grained fossiliferous limestone and shale, with ophiolitic melange beds with blocks of chert, flysch and volcanics. Miru Unit. 23 = Molasse. Interbedded coarse pebbly sandstones and siltstones and shales. Typical braided stream deposits. 15

A r o u n d Kargil a n d Dras, the D r a s unit consists m a i n l y of island arc andesitic a n d b a s a l t i c lavas, pillow lavas a n d tufts ( F r a n k et al., 1977; a u t h o r s ' observations), m e t a m o r p h o s e d to greenschist facies. As the w i d t h of e x p o s u r e of the Dras unit increases to the southeast, the p r o p o r t i o n of s e d i m e n t a r y rock increases; b y the time L a m a y u r u is reached very few volcanic flows occur in the sections. Nindam

flysch

N o r t h of L a m a y u r a most of the N i n d a m flysch consists of thinly b e d d e d flysch with varying p r o p o r t i o n s of unit varying p r o p o r t i o n s of tuff a n d lava (Fig. 8). The top of the section consists of a l t e r n a t i n g thinly b e d d e d and thickly b e d d e d tufts, volcaniclastic sandstones, shales a n d m i n o r lavas. Proceeding n o r t h w a r d s along the Y a p o l a river gorge, successively lower beds of the N i n d a m flysch are exposed. The s e d i m e n t s b e c o m e t h i n n e r b e d d e d , finer-grained with few p y r o c l a s t i c units a n d finally pass t r a n s i t i o n a l l y d o w n w a r d s into thinly b e d d e d flysch r e s e m b l i n g the L a m a y u r u flysch, though p e t r o g r a p h i c a l l y distinctive in its felspar c o n t e n t (Fig. 7). T h e s a n d s t o n e beds in the N i n d a m flysch are very variable. In unit 16, three facies are recognizable a n d show similarities to the t u r b i d i t e facies C, D a n d E (Mutti, 1977; Fig. 9A). U n i t 17 consists of very fine grained g r a d e d p o r c e l l a n e o u s tufts, of facies G, d e p o s i t e d from very dilute suspensions or s i m p l y by settling ash. Unit 18 consists of facies D, though with a few thicker s a n d s t o n e beds of facies C. However, unit 18 consists m o s t l y of classical thinly b e d d e d g r a d e d fine-grained s a n d s t o n e s a l t e r n a t i n g with shales (Fig. 9B). T h e y are typical distal, basin plain deposits.

263

Most of the Nindam flysch has similar characteristics to the above sections. It is mainly distal turbidites with subsidiary proximal turbidites and rare beds of channel origin. Thus the fan which fed them is not present in the preserved part of the Dras unit, at least in areas studied so far. All samples are poorly sorted felspathic greywackes in which the maximum grain size ranges between coarse and fine sand. The grains are sub-angular to subrounded, with the majority of lithic grains being mafic and intermediate volcanics, with minor silicic volcanics, sandstone, chert and argillite. Much of the matrix is argillaceous, but a certain proportion is "pseudomatrix" formed by the breakdown of lithic grains and unstable minerals. Chlorite and calcite are common secondary minerals. The composition of the lithic clasts, the predominance of felspar over quartz and the abundance of potassium felspar indicate that most of the Nindam flysch was derived from a volcanic terrain of mafic to intermediate composition. The wide range of composition on the QFL plot (Fig. 7) in part reflects the variation in maximum grain size in the samples studied. Only the coarsest greywackes lie in or near the field of magmatic arc provenance of Dickinson and Suczek (1979). Few greywacke suites are as plagioclase-rich as the Nindam flysch; though they are similar in composition to some of the greywackes of the Cretaceous Uyak Complex of Kodiak Island, Alaska, which have been interpreted as having been deposited in an oceanic trench adjacent to an active volcanic are (Connelly, 1978). Thus, the petrographic composition of the sandstones, the petrographic and chemical composition of the Dras volcanics and the interfingering of the Dras

Fig. 9. A. Nindam flysch, unit 16: thickest bed is 3 m thick. B. Nindam flysch, unit 18, base: thickest bed is 3 cm thick.

264 volcanics and N i n d a m flysch strongly suggest that the Nindam flysch was derived from an island arc of mafic to intermediate composition and that the Dras volcanics formed part of this arc. The very low quartz content and dominance of plagioclase suggests an immature island arc.

Khalsi unit This thrust sheet lies between ophiolitic melange on the south and molasse on the north (Fig. 10). Most of the unit is composed of interbedded coarse pebbly turbidite sandstones and shales, which we call the Khalsi flysch. This is the " I n d u s flysch" of Frank et al. (1977) and Fuchs (1979).

Khalsi flysch This flysch outcrops between Nurla and Khalsi and extends eastwards as far as Omlung in the Markha valley (Fig. 1). At Khalsi, it consists of turbidite fan conglomerates, interbedded with pelagic shales and thin graded sandstones and siltstones. Here, the flysch conformably overlies the Khalsi limestone, a shelf limestone of Aptian to Lower Albian age (Bassoullet et al., 1983), and is thus mid-Cretaceous and younger in age. At Shingo, the Khalsi flysch is finer grained and consists predominantly of thinly bedded calcareous fine-grained sandstone and calcareous shale, very similar in appearance to the Lamayuru flysch and the Eocene Jurutze flysch (p. 270): nevertheless its stratigraphic position above the Khalsi limestone and especially its distinctive petrography make it easily recognizable. Between Nurla and Khalsi, the Khalsi flysch consists of thickening and coarsening upward sequences of grey calcareous shales, thinly bedded conglomerate, conglomeratic sandstone and graded conglomerates. The massive conglomerates are tabular and grain-supported, with well-rounded pebbles up to 0.2 m in diameter in a matrix of poorly sorted argillaceous volcaniclastic green silty sandstone. The conglomerates are frequently graded and show pebble imbrication and channelling. The presence of belemnites in interbedded shales indicates marine conditions (Fuchs, 1979). These conglomerates are typical resedimented deposits inferred to be deposited on the upper parts of submarine fans (Walker, 1978). The three thickening and coarsening-upward sequences of the Khalsi flysch (Fig. 10) closely resemble the deposits of prograding deep-sea fans, in particular of prograding suprafan lobes on the middle parts of such fans (Normark, 1978; Walker, 1978; Nilsen and Abbott, 1981). The shale and thin sandstone units represent outer fan a n d / o r overbank deposits which were gradually buried by the advancing lobes. At Shingo, the Khalsi flysch consists of fine-grained calcareous sandstones which are parallel laminated, frequently graded, up to 10 cm thick, but often multiply stacked to a thickness of 2 m. There seems no regularity in these facies D sediments, which are probably deposited in a basin plain environment: they thus seem to

265 represent a more distal facies of the Khalsi flysch at Nurla and Khalsi. The conglomerates at Nurla and Khalsi contain rounded pebbles, whose characteristic composition is: 30% biomicrite limestone (Khalsi limestone), 40% intermediate volcanic and hypabyssal rocks (dominantly andesitic), 10% basalt, and 20% of miscellaneous rocks, dominantly red chert, vein quartz and acid intrusives. The conglomerate matrices and sandstones consist of very immature plagioclasedominated felspathic greywackes (Fig. 7) in which zoned plagioclase forms between 60 and 90% of the grains; quartz is rare or absent. Hornblende, clinopyroxene and biotite range up to 10%; potassium felspar is absent and olivine forms up to 1% of the grains. The matrices are very poorly sorted silty argillite, dominated by phyllosilicates many of which appear to have formed by the breakdown of unstable grains. The fine-grained greywackes at Shingo are the same, except for the presence of traces of plagioclase-bearing cherts. The Khalsi flysch at Nurla-Khalsi and Shingo form a nice deep-sea fan to basin plain assemblage (cf. Hsi3 et al., 1980). The rapid change from the shallow-water Khalsi limestone to the deep submarine fan environment of the Khalsi flysch suggests the collapse of a shallow shelf environment. The roundness of the pebbles and their composition suggest derivation from shallow-water gravel bars or beaches adjacent to a source including oceanic and island arc material, probably the Dras volcanics which are roughly the same age.

Miru unit

This unit lies almost entirely east of the Zanskar river (Pal and Mathur, 1977) and forms a huge anticlinorium of Tertiary, predominantly molasse, sediments. It gradually appears below the southeasterly trending thrust marking the northern edge of the Khalsi unit (Fig. 1t). Eocene shelf and flysch sediments form the core of the anticline from the Zanskar river eastwards to Miru. On the south these Eocene sediments pass gradually upwards into younger molasse, which is overthrust by the Khalsi unit (Brookfield, 1983). North of the anticlinorium axis, the Eocene sediments are unconformably overlain by a very thick younger Tertiary molasse sequence (Fig. 12), petrographically less mature than that south of the axis. A distinct break thus occurs between a core and southern flank sequence and a northern flank sequence. The core and southern flank sequence consists of a shelf-flysch-molasse transition, comprising the Basal clastics, Jurutze marls, Jurutze flysch, Stok Kangri Conglomerates and Kongmaru La molasse. The northern flank sequence is entirely thick continental molasse, comprising the Rumbok molasse, Zinchon molasse, Nimu Grits and Hemis Conglomerate (Table I). The core and southern flank sequence (Fig. 13) is intricately folded and faulted, especially at its base.

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Basal clastics At Rumbok, these consist of at least 400 m of red and yellow, very well sorted calcareous feldspathic and lithic greywackes and arenites, interbedded with sandy shales. The sandstones are usually parallel laminated and low-angle cross-laminated, in beds up to 2 m thick, sometimes stacked to 10 m. Interbedded thin sandstones and shales have mudcracks. Dainelli (1933-34) recorded bivalves and gastropods, including oysters, from the upper part of this sequence. These features suggest a marginal marine environment, possibly a lagoon.

270 To the west, in the Zanskar river gorge between Choksti and Sumdah Doh, Sterne (1979) described a facies change in these basal sediments: from south to north, in the cores of three successive anticlines, there was a change from maroon siltstones to grey, green and red sandstones to large cobble conglomerates containing "granitic" clasts which were interbedded with grey, green and brown sandstones. These sediments underlay the Jurutze marls and nummulitic limestone. The northward coarsening content of "granite" pebbles and the petrography of the sandstone suggest that this basal sequence was deposited in a marginal marine to terrestrial environment at the southern margin of a source mainly composed of sedimentary and igneous r o c k s - - p r o b a b l y the melanges and Dras unit of the Indus Zone. Jurutze marls These were first described by Dainelli (1933-1934) and named by Sterne (1979) and consist of about 400 m of alternating brownish, fine-grained calcareous sandstones, calcareous shales and thin bioclastic limestones. The limestones contain foraminifera of Middle Eocene (Lutetian) age (Dainelli, 1933-1934). Interbedded sandstones and shales contain abundant marine bivalves and gastropods, together with poorly preserved echinoids (Dainelli, 1933 1934; Sterne, 1979). At Jurutze, the marls pass up into the overlying Jurutze flysch: but, to the south the main mass of the Jurutze flysch is of Lower Eocene age. There must therefore be a lateral facies change of the basal clastics, and probably the Jurutze marls, into flysch. The sandstones are fine-grained, well sorted and planar to low-angle crosslaminated in multiple units up to 5 m thick; mudcracks and clay pebbles are common. Like the basal clastics, the Jurutze marls are marginal marine shallow-water sediments, but with a free connection to the open ocean, as shown by the foraminifera. Petrographically, the basal clastics and Jurutze marls are similar. In both, the sandstones are lithic and felspathic greywackes and arenites. Although the samples plot across the continental block and recycled orogen provenances of Dickinson and Suczek (1979), the recycled orogen provenance is, to a certain extent, indicated by the variety of trace grains found. These include olivine, spinel, epidote, sphene, zircon, dacite and spilite. Jurutze flysch This unit consists of thinly bedded, fine grained, calcareous lithic and quartz greywackes, alternating with thinly laminated calcareous shales and rare, thin foraminiferal limestones (Fig, 13). It has suffered intense polyphase deformation, thus the estimated thickness of 3000 m may be very inaccurate. South of Jurutze, the flysch transitionally overlies the Jurutze marls and passes gradually upwards into the Stok Kangri molasse. A large thrust sheet of Jurutze flysch to the south of this, however, yielded (surprisingly!) foraminifera of ?mid-Ilerdian to ?early Cuisian (i.e.

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Fig. 14. Petrography of the Eocene sections in the core and southern flank of the Miru anticlinorium. Legend as in Fig. 4. mid-Ypresian or early Eocene) age (Brookfield and Premoli-Silva, in prep.). Some of the flysch is therefore older than the Jurutze marls and possibly equivalent to the basal clastics. The sandstones are all fine-grained and finely laminated (Fig. 15A). Occasionally, small-scale cross-laminated sandstones show parting lineation and sole marks, and all may be classified as distal turbidites of facies D. Petrographically the samples are all arkosic and lithic wackes, with most of the lithic grains being limestone (Fig. 14), like the Basal clastics and Jurutze marls. Chert grains contain plagioclase microlites and there are rare basalt grains. The samples resemble deposits derived from the uplifted basement and foreland uplift provenances of Dickinson and Suczek (1979), but are slightly more mature than the Basal clastics of Jurutze marls, in keeping with their presumably more distal depositional environment.

Stok Kangri Conglomerates and Kongmaru La molasse These transitionally overlie the Jurutze flysch south of Rumbok, though we have not studied the transition in any detail. They are presumably late Eocene in age or younger. The Stok Kangri Conglomerates show a progressive change (Fig. 16) from large channels with epsilon cross-stratification and thick overbank deposits, typical of meandering streams (16A), through irregular fining-upwards cycles typical of braided

272

Fig. 15. A. Relatively thick-bedded Jurutze flysch at Chogdo. B, Central part of Stok Kangri molasse, 2 km north of Kongmaru La. Conglomeratic sandstone units are low-angle cross-bedded and 5 m thick. ( D o n j e k t y p e - - M i a l l , 1977) streams (Figs. 16B a n d 15B), into typical p r o x i m a l b r a i d e d s t r e a m of alluvial fan d e p o s i t s (16C; cf. H e w a r d , 1978). T h e s a n d s t o n e s are all lithic arenites a n d lithic wackes, in which limestone forms up to 85% of the grains. M a n y of the l i m e s t o n e grains c o n t a i n a b u n d a n t p l a g i o c l a s e felspar a n d small ? C r e t a c e o u s foraminifera, a n d were p r e s u m a b l y derived f r o m the C r e t a c e o u s K h a l s i L i m e s t o n e , or i n t e r b e d s in the K h a l s i flysch. D e s p i t e the c o a r s e n i n g - u p w a r d n a t u r e

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of the sequence, the sandstones become progressively more mature upwards (Fig. 14). This is reflected in a decreasing L v / L ratio, an increasing L s / L ratio and a decline in feldspar content. There is also a slight increase in metamorphic grains, though these are in such small amounts (less than 5%) that not much reliance can be placed on this. The upper part of the Stok Kangri Conglomerates represent a climax in tectonic uplift, since the overlying molasse--the Kongmaru La molasse--is much finer grained. The Kongmaru La molasse apparently conformably overlies the Stok Kangri Conglomerates and consists of brownish, fine-grained, well-sorted, channellized, festoon-cross-bedded sandstones with intraformational clay clasts, alternating with red siltstones, shales and thin, fine-grained sandstones. The sequence closely resembles the classical Devonian meandering stream fluviatile sequences described by Allen (1965). Baud et al. (1981) noted gastropods, bird tracks, plant and crustacean

274 remains and rain prints in the sediments. The sandstones are mature lithic and quartz arenites, closely resembling the sandstones of the Stok Kangri Conglomerates (Fig. 14). We interpret the Kongmaru La molasse to have been laid down by large, predominantly meandering streams in an alluvial plain some distance from the uplifts to the north. If plotted without their limestone grains, all these sediments fall in the recycled orogenic provenance of Dickinson and Suczek (1979). Only the two samples from the lowest beds of the Stok Kangri Conglomerates plot in the magmatic arc provenance. We consider that the sediments were derived from foreland uplifts of the Khalsi and Dras units backed by the developing Ladakh batholiths (which are partly late Eocene in age--Brookfield and Reynolds, 1981; Sharma et al., 1981). The increasing maturity of the sequence upwards, suggests that the foreland uplifts sealed off the Ladakh batholith source. The petrographic maturity of the above two molasse sequences is in strong contrast to the immaturity of the molasse units on the northern side of the anticlinorium, which unconformably overlie the Jurutze flysch and overlying mature molasse at Rumbok. The northern flank molasse sequence is an enormously thick sequence, apparently unconformable on the Eocene flysch, and thrusts northwards over the Ladakh Unit to the north (Figs. 11 and 12). It consists of complex, intricately folded and faulted molasse, in which stratigraphic relationships of the different units have not so far been accurately determined. Furthermore, apart from ?Oligocene plants from the Hemis Conglomerate (Sah and Sharma 1980) no diagnostic fossils have yet been found. The stratigraphic position of the molasse, unconformable on Eocene sediments and overlain by Pliocene valley gravels, indicates an Oligocene to Miocene age. We describe the molasse units from south to north, which is probably the stratigraphic sequence, and have given the units informal names, some of which have already been proposed by others.

Rumbok molasse This consists of alternating red and green, fine to medium grained felspathic sandstones and shales, overlain by medium-bedded, coarse to medium-grained, green felspathic sandstones and conglomeratic sandstones with interbeds of thin greenish siltstone and silty shale. North of Rumbok, the total thickness is about 300 m. To the east, at Chogdo, the lowermost red section is absent and the upper part rests on flysch correlated with the Jurutze flysch. Sandstones form about 70% of the section, are massive and tabular, generally in 1 m thick beds often multiply stacked to 5 m. Small-scale festoon cross-lamination occurs in some lensitic beds, but parallel lamination is more characteristic. The nature of the stratification and bed thickness, together with the few sedimentary structures recorded suggest deposition by small proximal braided streams.

275 Q

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Fig. 17. Petrography of the ?post-Eocenemolasse on the northern flank of the Miru anticlinorium. Legend as in Fig. 4. Petrographically the sandstones are arkosic arenites (Fig. 17) containing up to 20% of chert grains, and rare limestone grains. Strained and unstrained quartz grains are about equal in proportion. Potassium felspar is greater than or equal to plagioclase, and there are traces of muscovite, epidote, sphene and zircon. Zinchon molasse

This molasse is a distinctive unit, named after the village of Zinchon and consists of grey, green and occasionally red silty shales, interbedded with planar, tabular and festoon cross-bedded lithic and felspathic sandstones (Figs. 18 and 19A). Conglomerates are rare. The beds are arranged cyclically. Moderately well-sorted, low-angle cross-bedded conglomeratic sandstones with rounded pebbles, pass upwards into festoon crossbedded lithic sandstones, then into shales and silstones with thin graded fine-grained sandstones. Each cycle, where complete, is between 5 and 50 m thick. These cycles are typical of high-sinuousity large streams, probably with braided channels, with extensive floodplains. The Zinchon molasse contains a pebble suite predominantly derived from the Ladakh batholith complex to the north, though with minor pebbles derived from the Indus Zone units to the west. A typical pebble assemblage is: 55% acid volcanics, 20% quartz-diorite, 10% greywacke, and 5% limestone. The limestone grains contain Eocene foraminifera: the abundance of Eocene limestone clasts distinguishes the Zinchon molasse from the Nimu Grits and Hemis Conglomerate to the north.

276

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B

Gravel

I

Y Fig. 18. Typical sections of the ?post-Eocene molasse on the northern flank of the Miru anticlinorium.

Fig. 19. A. Zinchon molasse, south of Chogdo. Thickest sandstone is 5 m thick. B. Mimu Grits, north of Chogdo. Thinner sandstones in centre are 1-2 m thick.

277 The sandstones are feldspathic greywackes and quartz wackes (Fig. 17). They consist of sub-angular to rounded grains, with strained and unstrained quartz grains approximately equal in proportion, abundant micrite limestone grains (up to 30% of the grains) and traces of plagioclase, basalt, epidote, muscovite, sphene and zircon. The sandstones are moderately to poorly sorted with detrital matrix of silt and clay, cemented by calcite. Nimu Grits These were named by Sterne (1979) from Nimu village. The Nimu Grits consist of over 1500 m of thick tabular and festoon cross-bedded coarse conglomerates, granular low angle tabular and festoon cross-bedded sandstones silty shales and siltstones, with thin graded fine-grained sandstones (Figs. 18 and 19B). The conglomerates and sandstones become thinner and finer-grained upwards. These sediments are well-exposed on the northern side of the Indus at its junction with the Zamskar river and grade downwards into the Zinchon molasse with increasing thickness of carbonaceous silty shales and the disappearance of thick conglomerates. Cross-bedding indicates southwesterly to southeasterly current flow. Although similar to the Zinchon molasse in their pebble composition, the sandstones are much less mature, consisting of arkosic wackes (Fig. 17). They differ from the Hemis Conglomerate in their abundance of quartz diorite pebbles. The Nimu Grits represent deposits of large braided streams with extensive floodplains. Their petrography indicates that they were derived mostly from the Ladakh batholith. Hemis Conglomerate Named by Frank et al. (1977), this unit is at least 2000 m thick and probably Oligocene in age (Sah and Sharma, 1980). It consists of regular alternations of thick conglomerate, sandstone and shale (Fig. 20), in two contrasting sedimentary sequences separated by a fault at Hemis monastery. Near the monastery, the first sequence (Fig. 18A) consists of at least 1000 m of thick-bedded, well-sorted, tabular, horizontal to low-angle cross-bedded and festoon cross-bedded, granular relatively well-sorted coarse- to medium-grained sandstones. The dominant current flow is between north and northeast. This sequence, composed dominantly of Gm gravel is characteristic of proximal braided streams (Rust, 1979) of Scott type (Miall, 1977), representing a low ratio of mean particle size to water depth. Upstream from the monastery, the second sequence consists of over 1000 m of thick, fining upward cycles (Fig. 18B) characteristic of distal braided rivers (Rust, 1979). The pebble compositions indicate derivation both from the Ladakh batholith unit and the Indus zone. A typical pebble assemblage consists of about 60% granodiorite, quartz diorite, tonalite and diorite; 20% of basic to intermediate rocks, mostly basalt,

278

spilite, andesite and dacite; 10% red and grey chert; and 10% greywacke sandstone, together with minor agglomerate limestone and argillite. The sandstones are predominantly arkoses, with a few lithic arenites (Fig. 17). Quartz grains are mostly strained. Potassium felspar is about equal to plagioclase and is perthitic or microcline. Chert ranges up to 10% and there are traces of microlitic and epidotized basalt, granophyre, quartzite, cherty limestone, greywacke sandstone, siltstone, biotite, epidote, olivine and glaucophane. The Hemis Conglomerate thus appears to have been laid down by proximal shallow, and distal, large (up to 10 m deep) braided streams flowing north and northeast, and draining both the Indus Zone and the Ladakh Batholith Zone.

Interpretation of the Miru anticlinorium sequence The sequence on the southern flank and core of the anticlinorium represents the filling of a fore-deep in front of uplifts to the north. The ?latest Paleocene or ?earliest Eocene to latest Eocene phase, represented by the lateral passage from shallow marine shelf to deep shelf deposits and upwards into molasse, is attributed to the development of foreland uplifts at the northern margin of the Indian plate, possibly due to the initial emplacement of the Indus Zone units. The younger, coarser post-Eocene molasse on the northern flank of the anticlinorium represents detritus from much more extensive uplifts, and includes detritus derived from both the Indus and Ladakh batholith units, with current directions from both north and south. This post-Eocene molasse seems to have been deposited by very large streams flowing laterally in front of uplifts on both north and south, and interfingered with large alluvial fans coming off these uplifts. We attribute this to final emplacement of the Indus Zone units in the late Eocene and the development of the Ladakh batholith complex to the north as a major magmatic arc on the northern edge of the Indian plate (cf. Andrews-Speed and Brookfield, 1982). The sequence in this fore-deep, from shelf to flysch to molasse, can be likened to the development of other fore-deeps in the geological record, in particular: the Appalachian fore-deep in the Devonian, the Alpine fore-deep in the early Tertiary and the Canadian Rocky Mountain fore-deep in the Cretaceous. L A D A K H BAT HOL ITH Z O N E

This consists of an acid to intermediate magmatic arc, with small remnants of autochthonous molasse resting unconformably along its southern, faulted, margin

Fig. 20. Hemis Conglomerate, near Hemis. A. Large-scale cross-bedded conglomerate on top of floodplain siltstones, shales and thin sandstones: bar scale is 5 m long. B. Thickly bedded orthoconglomerates: bar scale is 5 m long. C. Detail of orthoconglomerate: bar scale is 10 cm long. Note variety of pebble compositions, but dominated by basic volcanics and leucocratic quartz-diorites. D. Low-angle crosslaminated and cross-bedded sandstones and conglomerates, forming couplets: ?longitudinal bars. Pen is 15 cm long.

279

280

Fig. 21. Upshi molasse. A. General view; dotted line marks contact with Ladakh batholith. B. Fine-grained arkoses and siltstones at contact with Ladakh batholith; bar scale is 5 m long; C, Debris flow conglomerates at top of B sequence. D. Coarsening-upwards cycles; above B sequence; bar scale is 10 m tong. E. Tabular cross-bedding in arkoses of D.

with the Indus zone. Much of this molasse is analogous to the Tertiary molasse of the Miru anticlinorium and has been described in detail elsewhere (Brookfield and Andrews-Speed, in press). At Upshi, west of Leh, however, a fine alluvial fan sequence can be related to uplift of the Ladakh Batholith Zone and has no equivalents or analogies in the Miru sequence.

Upshi molasse First noted by Frank et al. (1977), this unit consists of conglomeratic granular arkose, pebbly sandstone and sandy silty shale (Fig. 21) arranged in thick, coarsening upwards sequences up to 20 m thick (Fig. 22). The beds dip steeply south and rest unconformably on an irregular surface of the Ladakh batholith. No fossils are recorded: a lignite layer seen in the banks of the Indus river may provide an age (we

281 could not gain access to this locality). However, the Upshi molasse is probably post-Oligocene, since the Ladakh batholith has been dated as late Eocene to Oligocene (Brookfield and Reynolds, 1981; Sharma et al., 1981). Stacked coarsening-upwards cycles of this type are typical of alluvial fans. The apparent absence of debris flows and the thinness of the cycles suggest relatively Maximum grain size Silt/ Clay I Sand ]Gravel m

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Fan head incised channel with debris flows

Fig. 22. Section of Upshi molasse, near Upshi.

282 Q

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Wakka Chu molasse

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WAKKA CHU MOLASSE Qp/Q PIF

Ls/L LvlL Matrix

UPSHI M O L A S S E 0.1-0.2 (mean 0.13) 0.3-0,4 (mean 0.35)

UNIT 1 0-0,05 (mean 0.02) 0.82-0.93 (mean 0.88)

UNIT 2 002-0.12 (mean 003) 079-0.92 (mean 0.89)

UNIT 4 0-02 (mean 0,06) 06-0.97 (mean 0.84)

0 1.0 detrital: carbonate 10-15% 12-19%

0 1.0 detrital 9-28%

0 t0 detrital 5-11%

0 10 detrital 10-20%

Plagioclase

Qp/Q PIK Ls/L Lv/L Matrix

UNIT 5(a) UNIT 5(b) 0.1.0.5 (mean 0.4) 0.3-0.6 (mean 0,4) 0.4-0,5 (mean 0.44) 0.3-0,4 (mean 0.38) 0-0.4 (mean 0.1) 0-0.1 (mean 0.02) 0.1-1.0 (mean 0.6) 0-1,0 (mean 0.8) detrital 2*23% (mean 9} detrital 3-19% (mean 9) (mean 11)

Plagioclase

An20_40

An20.40

UNIT 6 05-06 (mean 0.57) 04.0.5 (mean 0.63) 0.0.4 (mean 0.27) 06.0.8 (mean 0.67) carbonate 3-15% An20.40

Fig. 23. Petrography of Upshi molasse, and Wakka Chu molasse at Kargil. Legend as in Fig. 4.

"wet" conditions. The thinning-upwards of the cycles suggest retreat of the fan which gave rise to them over the course of time. The overlying beds along the Indus river (which we could not examine closely) consist of tabular bedded fine-grained to coarse grained arkosic sandstones suggestive of sand bed ephemeral stream deposits. The pebbles and boulders consist entirely of rounded exfoliated granodiorite with minor diorite, derived from the Ladakh batholith to the north. The sandstones are all coarse, moderately sorted arkoses (Fig. 23). Further west, in the Kargil area, the Wakka Chu molasse (Brookfield and Andrews-Speed, in press) consists of ephemeral stream deposits (unit 1), passing up into meandering stream, deltaic and lacustrine deposits (units 2-4), which in turn are overlain by Miocene ephemeral stream, meandering stream and alluvial fan deposits (units 5 and 6). Petrographically, these autochthonous molasse sediments closely resemble the Miru anticlinorium sequence (Fig. 23); though slightly greater immaturity is in keeping with their proximity to the Ladakh batholith and Indus Zone sources. CONCLUSIONS

There is little sign of any immature clastics on the northern Indian plate margin (Tethyan Zone) before the latest Palaeocene. The Tethyan Mesozoic sequence

283 consists dominantly of mature clastics and carbonates. Nevertheless, there are indications of a source change between the Lower Cretaceous Guimal sandstones and the Upper Cretaceous Kangi La flysch. The former indicates a southerly derivation from the Indian Shield; the latter from basement uplifts with limestone cover to the north. The first sign of ophiolitic melange derived material is in the .'?Eocene molasse on the southern side of the Miru anticlinorium. This suggests that the late Cretaceous initial emplacement of the ophiolitic melanges indicated by radiometric dating (Brookfield and Reynolds, 1981; Desio and Shams, 1980) did not form sub-aerial uplifts, though, from the Upper Cretaceous to ?Lower Eocene petrographies of the Kangi La flysch, .'?Basal Eocene clastics and Eocene shelf and flysch deposits, it did lead to deformation and uplift of the northern Indian continental margin, and a little detritus from the Dras and Khalsi units. The onset of ophiolitic-derived detritus in the ?Eocene molasse, together with the radiometric evidence for the start of development of the Ladakh batholith complex in the late Eocene, suggest that by this time uplift of the already assembled Lamayuru, Dras and Khalsi allochthons was taking place. Since ophiolitic and Dras volcanic detritus only occurs abundantly in the ?Eocene molasse and since the Spongtang Klippe lies on an Eocene sequence in the Tethyan zone, we suggest that the development of the Ladakh Andean arc led to southward gravity spreading of already assembled Indus Zone allochthons (Lamayuru, Dras and Khalsi units) and the Spongtang Klippe, due to uplift of the Ladakh batholith complex starting in the late Eocene-early Oligocene. This uplift also caused deformation of the Eocene shelf-flysch-molasse sequence of the Miru anticlinorium which is unconformably overlain by younger molasse. The younger Tertiary molasse of the Miru anticlinorium and Ladakh batholith complex of post late Eocene age forms a complex of alluvial fan, braided stream and meandering stream deposits which were derived both from the Zanskar Range to the south and the Ladakh Batholith Zone to the north, as well as from Indus Zone units already tectonically emplaced. This molasse seems to represent deposition in a successor basin lying between the Indian plate to the south and the rising Ladakh batholith unit to the north. It most closely resembles the back arc basins of the Andes and the foredeeps of the Canadian Rocky mountains and Alps, as well as the present foredeep in front of the rising Himalaya. The increasing content of detritus, from both the Ladakh batholith and the Indus Zone units in the younger Tertiary molasse, suggests telescoping of the fore-deep in Oligocene to Miocene times, due to progressive southward thrusting and particularly to uplift of the Himalaya along the Main Central Thrust in the Miocene. By post-Miocene times, this uplift had led to extensive northward backthrusting of all units north of the Himalaya. Evidence for the younger Miocene phases are to the north, along the Shyok melange and Karakorum zones, which are beyond the scope of this paper (Brookfield, 1981).

284 ACKNOWLEDGEMENTS Field work by M.E.B. was funded by N.S.E.R.C. (Canada) and by the National G e o g r a p h i c Society. H e wishes to a c k n o w l e d g e the assistance of M a r k Spurgeon, R o b e r t F o r t u n e a n d m a n y o t h e r s w h o h e l p e d w i t h c a r r y i n g r o c k s at d i f f e r e n t t i m e s , as well as t h e g r e a t h o s p i t a l i t y o f v i l l a g e r s a n d t h e i r f a m i l i e s w h o g a v e s h e l t e r a n d f o o d , b o t h in L a d a k h a n d B a l t i s t a n . REFERENCES Allen, J.R.L., 1965. Fining upwards cycles in alluvial successions. Geol. J., 4: 229-246. Andrews-Speed, C.P. and Brookfield, M.E., 1982. Middle Palaeozoic to Cenozoic geology and tectonic evolution of the northwestern Himalaya. Tectonophysics, 82: 253-275. Bassoullet, J.P., Colchen, M., Marcoux, J. and Mascle, J., 1978a. Une transversale de la zone de l'Indus de Khalsi h Photaksar, Himalaya du Ladakh. C.R. Acad. Sci. Paris, Ser. D, 287: 563-566. Bassoullet, J.P., Colchen, M., Guex, J., Lys, M., Marcoux, J. and Mascle, G., 1978b. Permien terminal n6ritique, Scythian p61agique et volcanisme sous-marin, indices de processus tectono-s6dimentaires distensifs h la limite Permien-Trias dans un bloc exotique de la suture de l'Indus (Himalaya du Ladakh). C.R. Acad. Sci., Set. D, 287: 675-676. Bassoullet, J.P., Colchen, M., Marcoux, J. and Mascle, G., 1980. L'6difice de nappes du Zanskar (Ladakh, Himalaya). C.R. Acad. Sci., Ser. D, 290: 389-392. Bassoullet, J.P., Colchen, M., Marcoux, J. and Mascle, G., 1981. Les masses calcaires du flysch Triasico-Jurassique de Lamayuru (Zone de la suture de l'Indus, Himalaya du Ladakh): Klippes s6dimentaires et 616ments de plate-forme remanies. Riv. ltal. Paleontol., 86:825 844. Bassoullet, J.P. et al., 1983. Geological observations on the Indus Suture zone, Ladakh. Contrib. Himalayan Geol., 2, in press. Baud, A., Arne, B., Bugnon, P., Crisinel, A., Dolivo, E., Escher, A., Hammerschlag, J.C., Marthaler, M., Masson, H., Stech, A. and Tieche, J.C., 1981. Le contact Gondwana-Peri Gondwana dans le Zanskar oriental (Ladakh Himalaya). Inst. Mus. Geol., Universit6 de Lausanne, 32 pp., 18 figs. Baud, A. et al., 1983. Geological observations in eastern Ladakh. Contrib. Himalayan Geol., 2, in press. Brookfield, M.E., 1981. Metamorphic distributions and events in the Ladakh Range, Indus Suture Zone and Karakorum Mountains. In: P.S. Saklani (Editor), Metamorphic Tectonites of the Himalaya. Today and Tomorrow's, New Delhi, pp. 1-14. Brookfield, M.E., 1983. Reconnaissance geology of the area between Leh and the Markha valley, Ladakh. Contrib. Himalayan Geol., 2, in press. Brookfield, M.E. and Andrews-Speed, C.P., in press. Sedimentology of the Wakka Chu Molasse (Tertiary), Kargil, Ladakh, N.W. India. Geol. Rundsch. Brookfield, M.E. and Premoli-Silva, I., in prep. Eocene foraminifera from the lower Tertiary section around Rumbok, Ladakh, N.W. India and their palaeogeographical significance. Brookfield, M.E. and Reynolds, P.H., 1981. Late Cretaceous emplacement of the Indus Suture Zone ophiolitic melanges and an Eocene-Oligocene magmatic arc on the northern edge of the Indian plate. Earth Planet. Sci. Lett., 55: 157-162. Brookfield, M.E. and Westermann, G.E.G., 1982. Mesozoic ammonites from the Spong valley, Zanskar, Ladakh, N.W. India. J. Geol. Soc. India, 23: 263-6. Connelly, W., 1978. Uyak Complex, Kodiak Islands, Alaska: a Cretaceous subduction complex. Geol. Soc. Am. Bull., 89:755 769. Dainelli, G., 1933-1934. La Serie dei Terreni: Sped. Ital. de Filippi nel' Himalaya, Caracorum e Turchestan cinese (1913-1914), Ser. 2, Result. Geol. Geogr., 2 (1), 458 pp.

285

Desio, A. and Shams, F.A., 1980. The age of the blueschists and the I n d u s - K o h i s t a n Suture Line, N.W. Pakistan. Accad. Naz. Lincei, Rome; Class. Sci. Fis. Mat. Nat., Atti Rend., 68: 74-79. Dickinson, W.R., 1970. Interpreting detrital modes of greywacke and arkose. J. Sediment. Petrol., 40: 695-707. Dickinson, W.R. and Suczek, C.A., 1979. Plate tectonics and sandstone composition. Bull. Am. Assoc. Pet. Geol., 63: 2164-2182. Frank, W., Gansser, A. and Trommsdorf, V., 1977. Geological observations in the Ladakh area (Himalayas), a preliminary report. Schweiz. Mineral. Petrogr. Mitt., 5 7 : 8 9 113. Fuchs, G., 1977. Traverse of Zanskar from the Indus to the Valley of K a s h m i r - - a preliminary note. Jahrb. Geol. Bundesanst., 120:219 229. Fuchs, G., 1979. On the geology of western Ladakh. Jahrb. Geol. Bundesanst., 122: 513-540. Gaetani, M., Nicora, A. and Premoli-Silva, I., 1980. Uppermost Cretaceous and Paleocene in the Zanskar Range ( L a d a k h - - H i m a l a y a ) . Riv. Ital. Paleontol., 86: 127-166. Gaetani, M. et al., 1983. Late Cretaceous to Palaeocene foraminifera from Ladakh, N.W. India. Bull. Ital. Paleontol., in press. Gansser, A., 1964. Geology of the Himalayas. Wiley-Interscience, London, 289 pp. Gansser, A., 1977. The great suture zone between Himalaya and T i b e t - - a preliminary account. Colloq. Int. C.N.R.S., 268, Ecologie et Gbologie de l'Himalaya, pp. 181-191. Gansser, A., 1980. The significance of the Himalayan Suture Zone. Tectonophysics, 62: 37-52. Heward, A.P., 1978. Alluvial fan sequence and megasequence models: with examples from Westphalian D - S t e p h a n i a n B coalfields, Northern Spain. Can. Soc. Petrol. Geol. Mem.~ 5: 669-702. HsiL K.J., 1970. The meaning of the word flysch - a short historical search. Geol. Soc. Can., Spec. Pap., 7: 1-11. Hsu, K.J., Kelts, K. and Valentine, J,W., 1980. Resedimented facies in Ventura Basin, California, and a model of longitudinal transport of turbidity currents. Bull. Am. Assoc. Pet. Geol., 64: 1034-1051. Johnson, H.D., 1978. Shallow siliciclastic seas. In: H.G. Reading (Editor), Sedimentary Environments and Facies. Elsevier, New York, N.Y., pp. 207-258. Kreisa, R.D., 1981. Storm-generated sedimentary structures in subtidal marine facies with examples from the Middle and Upper Ordovician of southwestern Virginia. J. Sediment. Petrol., 51 : 823 848. Matter, A., Homewood, P., Caron, C., Rigassi, D., Van Stuijvenberg, J., Weidmann, A. and Winkler, W., 1980. Flysch and Molasse of Western and Central Switzerland. 26th Int. Geol. Congr. Guideb., G10, pp. 261-293. Miall, A.D., 1977. A review of the braided-river depositional environment. Earth-Sci. Rev., 13: 1-62. Mitchell, A.H.G. and Reading, H.G., 1978. Sedimentation and tectonics. In: H.G. Reading (Editor), Sedimentary Environments and Facies. Elsevier, New York (N.Y.), pp, 439-476. Mutti, E., 1977. Distinctive thin-bedded turbidite facies and related depositional environments in the Eocene Hecho group (south-central Pyrenees, Spain). Sedimentology, 24: 107-131. Nilsen, T.H. and Abbott, P.L., 1981. Paleogeography and sedimentology of Upper Cretaceous turbidites, San Diego, California. Bull. Am. Assoc. Pet. Geol., 65: 1256-1284. Normark, W.R., 1978. Fan valleys, channels, and depositional lobes on modern submarine fans: characters for recognition of sandy turbidite environments. Bull. Am. Assoc. Pet. Geol., 62:912 931. Odum, I.E., Doe, T.W. and Dott Jr., R.H., 1976. Nature of feldspar-grain size relations in some quartz-rich sandstones. J. Sediment. Petrol., 46: 862-870. Pal, D, and Mathur, N.S., 1977. Some observations on stratigraphy and structure of Indus Flysch, Ladakh region. Himalayan Geol., 7: 464-478. Robertson, A.H.F. and Woodcock, N.H., 1979. Mamonia complex, southwest Cyprus: evolution and emplacement of a Mesozoic continental margin. Geol. Soc. Am. Bull., 90: 651-665. Rupke, N.A., 1978. Deep clastic seas. In: H.G. Reading (Editor), Sedimentary Environments and Facies. Elsevier, New York, N.Y., pp. 372-415.

286

Rust, B.R., 1979. Coarse alluvial deposits. In: R.G. Walker (Editor), Facies Models. Geol. Assoc. Can., Ont., pp. 9-21. Sah, S.C.D. and Sharma, K.K., 1980. Fossil Palm from Hemis Conglomerate of Ladakh and its significance on the age of the beds. XI Himalayan Geol. Sere. Dehradun, 1980, p. 22 (abstract). Searle, M.P., 1983. Stratigraphy, structure and evolution of the T i b e t a n - T e t h y s zone in Zanskar and the Indus suture zone in the Ladakh Himalaya. Trans. R. Soc. Edinburgh, Earth Sci., 73: 205-219. Sharma, K.K., Sharma, O.P., Choubey, Vinay M. and Nagpaul, K.K., 1981. Age of the Ladakh-Deosai granite batholith, Trans-Himalaya. Curr. Sci., 50: 819-821. Sterne, E.J., 1979. Report on geological traverses across the l n d u s - T s a n g p o Suture Zone in Ladakh, northern India. B.A. (Hon.) Thesis, Harvard Univ., Cambridge, Mass., 66 pp (unpublished). Triampy, R., 1980. An outline of the geology of Switzerland. 26th Int. Geol. Congr. Guideb., G-10, pp. 1-104. Walker, R.G., 1978. Deep-water sandstone facies and ancient submarine fans: models for exploration for stratigraphic traps. Bull. Am. Assoc. Pet. Geol., 62: 932-966. Walker, R.G. and Mutti, E., 1973. Turbidite facies and facies associations. In: G.V. Middleton and A.H. Bouma (Editors), Turbidites and Deep-water Sedimentation. S.E.P.M., Pac. Sect., Short Course, Anaheim, Calif., pp. 119-157. Wells, N.A., 1983. Transient streams in sand-poor redbeds: early-Middle Eocene Kuldana Formation of northern Pakistan. Int. Assoc. Sedimentol. Spec. Publ., 6: 393-403.