the quaternary glacial history of nanga...

*Corresponding author. Tel.: 909-787-3434; fax: 909-787-4324.E-mail address: [email protected] (L.A. Owen).

Quaternary International 65/66 (2000) 63}79

The Quaternary glacial history of Nanga Parbat

Lewis A. Owen!,*, Christine H. Scott", Edward Derbyshire#!Department of Earth Sciences, University of California, Riverside, CA 92521-0423, USA

"Department of Geography, University of Leicester, Leicester LE1 7RH, UK#Department of Geography, Royal Holloway, University of London, Egham Surrey, TW20 0EX, UK

Abstract

During one or more times throughout the Quaternary, an extensive glacier system occupied the valleys of the Nanga Parbat massif.Glacial landforms in the Astor valley provide evidence for two separate glacial advances with ice advancing more than 15 kmdown-valley from the present ice fronts. Elsewhere in the massif, geomorphic and sedimentological evidence provide evidence fora less extensive glaciation, where glaciers advanced no more than 12 km beyond their present positions. Intense erosion and massmovement has destroyed any depositional evidence for earlier Pleistocene glaciations. However, truncated spurs, hanging valleys,steep valley sides and over-deepened trunk valleys provide evidence of an earlier, more extensive glaciation. Small moraines near thesnouts of the present glaciers provide evidence for at least three limited glacial advances that post-date the extensive valley glaciersystem. On the basis of geomorphology, sedimentology and relative weathering characteristics glacial landforms are correlated acrossthe Nanga Parbat massif. Furthermore, the age of the maximum extent of valley glaciation is tentatively assigned to early in the lastglacial cycle with two late Pleistocene readvances or periods of stagnation followed by three periods of limited glacial advance duringthe Holocene. ( 2000 Elsevier Science Ltd and INQUA. All rights reserved.

1. Introduction

Nanga Parbat is a relatively isolated massif at thewestern end of the Great Himalaya (Fig. 1). It comprisesa series of high peaks ('8000 m) that are bounded bythe Main Mantle Thrust. Although it has attracted muchattention from structural geologists, relatively little workhas been undertaken on the glacial geology. The valleysradiating from the Nanga Parbat Massif contain exten-sive accumulations of Quaternary glaciogenic sediments.Previous glacial geologic work has concentrated on theRakhiot valley (Sloan et al., 1998) and the middle Indusvalley, north of the Nanga Parbat massif (Owen, 1988,1989; Shroder et al., 1989, 1993; Richards et al., 2000a,b).Research into the genesis of thick sedimentary depositsin other northwest Himalayan regions such as SwatKohistan (Porter, 1970), the Hunza valley (Derbyshireet al., 1984), the Gilgit-middle Indus region (Owen,1988; Shroder et al., 1989), Kashmir (Holmes, 1988)and Lahul (Owen et al., 1996, 1997; Sharma and Owen,1996) has attributed these sediments to a series ofQuaternary glacial #uctuations. This research has led

to the development of various stratigraphical frame-works for the Himalaya, as summarized in Fig. 1.Although these stratigraphical models do not correlate indetail, they present a broad picture of Quaternaryhistory, involving major ice advances throughout thePleistocene, with progressively smaller advances towardsthe present. This paper summarizes the "eld evidence forQuaternary glaciations around Nanga Parbat. It pro-vides a framework for the chronology of glaciation in thisregion, but one that needs to be rigorously constrainedusing absolute dating techniques.

2. Methods

Four valleys, the middle Astor, the Rupal, the Rakhiotand the Rama, were chosen for detailed study (Fig. 2).Finsterwalder's 1 : 50,000 scale topographic map wasused as a base for geomorphic mapping, and glaciallandforms and sediments were mapped using the stan-dard techniques of Derbyshire et al. (1984) and Owen(1988, 1991). Using the methods of Owen (1994), greatcare was taken in distinguishing between glacial andnon-glacial diamicts in this region because of the wide-spread mass movement and rapid resedimentation ofdeposits. Standard sedimentary logging techniques were

1040-6182/00/$20.00 ( 2000 Elsevier Science Ltd and INQUA. All rights reserved.PII: S 1 0 4 0 - 6 1 8 2 ( 9 9 ) 0 0 0 3 7 - 3

Fig. 1. Relative chronologies and dates for glaciations in Northern Pakistan. (a) OSL dates and relative chronologies for Northern Pakistan afterRichards et al. (2000a), (b) Hunza valley after Derbyshire et al. (1984), (c) Lahul Himalaya after Owen et al. (1997), (d) Garhwal Himalaya after Sharmaand Owen (1996) and (e) Khumbu Himal after Richards et al. (2000b) (NP"Nanga Parbat).

used (Tucker, 1982; Eyles et al., 1983) on sections wheredirect measurement was possible. On many faces wheredirect measurement was rendered impossible by landownership constraints, or extremely di$cult terrain,photogrammetric techniques were used to determine ver-tical distances, supplemented by "eld sketches. Care wastaken in the construction of sedimentary logs to includeany lateral variation along with vertical variation. Thisallowed the facies to be interpreted using the methodsdescribed by Eyles et al. (1983) and Shaw (1986). Sedi-ments consisting of grains coarser than 5 mm in diameterwere classi"ed in the "eld on the basis of particle size(Wentworth, 1922). Particle shape was estimated usingZingg's (1935) and Powers' (1953) visual comparisoncharts. Particle size distributions were determined in thelaboratory on selected samples by a combination of wetand dry sieving (British Standards Institute, 1975). Orien-tated blocks of sediment were prepared and their micro-fabrics were studied in the scanning electron microscope(SEM) using the methods of McGown and Derbyshire(1977).

Relative dating was used to arrive at a temporal subdi-vision of the sedimentary units, based on the premise thatrock weathering, soil development and biological growthare time dependent. Where e!ects of non-temporal fac-tors such as altitude are minimized, any di!erences inrelative dating can be used as a re#ection of age. Thetechniques used in this study follow those used by Porter(1970) in Swat Kohistan, the International KarakoramProject (Derbyshire et al., 1984) in the Hunza valley,Holmes (1988) in Kashmir, and Shiraiwa and Watanabe(1991) in the Langtang Valley, Nepal. This study useda multi-parameter approach which increases the quantityand the quality of the data and strengthens the conclusions.

Morphostratigraphy and the principle of superposi-tion (Porter, 1970; Derbyshire et al., 1984; Owen, 1988;Shiraiwa and Watanabe, 1991) were used to distinguishbetween sedimentary units and to form an outline chro-nology. Rock varnish was used as an indicator of therelative age of a particular surface using the index de-veloped by Derbyshire et al. (1984). Clast weathering wasused successfully by Shiraiwa and Watanabe (1991) to

64 L.A. Owen et al. / Quaternary International 65/66 (2000) 63}79

Fig. 2. Location of the detailed study areas in the Nanga Parbat massif.

Fig. 3. Geomorphological map of the Astor valley.

distinguish between sedimentary units of di!erent ages.Using their criteria, weathering ratios in the form of thenumber of unweathered : jointed : disintegrated clastswere obtained by measuring 50 clast samples at the rockvarnish sampling sites in the Rakhiot and Lower RupalValleys. A second value of clast weathering within sedi-mentary units was obtained by measuring the percentageof clasts which are #aked and split and those which arepitted. Although found to be an unsatisfactory techniqueby Porter (1970) in Swat Kohistan, such measurementswere used successfully by Derbyshire et al. (1984) in theHunza valley. Following the criteria of the latter authors,values for the percentages of #aked and split boulders,and pitted boulders were also obtained from the rockvarnish sampling sites in the Rakhiot and Lower RupalValleys.

3. Middle Astor valley

The geomorphology and sedimentology of the middleAstor valley is shown in Fig. 3. Evidence of glacial ero-sion and deposition is present at two altitudes on thevalley sides (Fig. 3). The highest evidence on the valleysides is a clear break in slope, which can be identi"ed atapproximately 300 m above the valley #oor. This feature,although intermittent throughout the valley, forms

a well-de"ned high-level bench which can be seen aboveKine Das (2900 m), Danal (2900 m) and Finah (2600 m)on the east side of the valley and at Astor (2600 m), Idgah(2800 m), and at Parshing (2900 m) and Partabgarh(2700 m) on the west side (Fig. 3). It can be traced asa break in slope down the Astor valley to Harchu, 9 kmnorth of Astor. At Kine Das, Partabgah and Idgah,compact bouldery diamictons are present on the benches.These poorly sorted deposits appear, on the basis of "eldobservations, to be meltout till. They contain large angu-lar clasts which exhibit edge rounding within a predomi-nantly "ne-grained matrix. Particle size analysis of theKine Das deposit (Fig. 4A) shows that, whilst mostof the material is texturally similar, there are localizedareas within the massive structure where "ne silts andclays have been depleted. SEM analysis shows the micro-fabric to exhibit irregularly orientated sub-vertical`pseudoshearsa (Table 1), which are likely to be the result

L.A. Owen et al. / Quaternary International 65/66 (2000) 63}79 65

Fig. 4. Particle size distribution envelopes for glacial and lacustrinedeposits in the middle Astor valley, (A) valley side deposits and(B) valley #oor deposits.

of irregular settling of material (e.g. Owen, 1991). Thiscombination of evidence con"rms the initial "eld identi-"cation of the material on these benches as meltout till.The post-maximal rock varnish present on the surfaces ofthe large boulders within these deposits, following thecriteria of Derbyshire et al. (1984), suggests they are ofconsiderable age.

A second series of terrace deposits, 100 m above the#oor of the Astor valley, consist of poorly sorted diamic-ton (Fig. 3). These can be seen at Danal (2743 m), Finah(2342 m), Kine Das (2400 m), Guricot (2351 m) andKhirim (2550 m), but cannot be traced beyond Astor. Inthe "eld these appear to be tills, containing many large(with long axes of up to 40 cm) and medium sized clastswith rounded edges, within a silt-rich to sandy matrix.The presence of some localized and crude sub-horizontallayering within the massive structure of these units sug-gests they may be of meltout origin. Particle size analysisof the matrix suggests that the material is poorly sortedwith localized areas where silt and clay particle sizes areless abundant (Fig. 4). Microfabric analysis under the

SEM reveals the alignment of clays within this till, form-ing pseudoshears (Table 1), which are documented fea-tures of downwasting (Owen, 1991). Again this is inagreement with the identi"cation of these deposits asmeltout tills (Owen, 1991).

At Gehrak, a low terrace of glacial sediments forms aninlier within valley side deposits (Fig. 3). These depositsare overlain by colluvial sediments (Fig. 5), the contactbetween the two materials being sharp. The colluviumconsists of poorly sorted massive and strati"ed diamic-tons with similar particle size characteristic to meltouttills. The clasts within the colluvial deposits are disposedsub-horizontally and are more angular in shape thanthose of the underlying meltout till, which is more com-pact and poorly sorted, and contains clasts with roundededges. It exhibits no strati"cation.

A material texturally similar to the tills forming theselower terrace deposits was found at Kine Das (2400 m). Ithas a well de"ned ridge morphology and lies approxi-mately 100 m above the valley #oor, and is over 500 mlong. Its "nes-rich matrix and large clasts suggest a gla-cial origin, but its distinctive morphology is not consis-tent with the meltout process. Particle size analysis ofmatrix samples showed the material to be texturallyuniform, with no signi"cant localized sorting within thedeposit. Large exposed boulders within this lateral mo-raine show advanced surface weathering with post-maxi-mal rock varnish.

The presence of glaciogenic deposits at two distinctlevels on the sides of the middle Astor valley suggests twostages of glaciation. For the ice to have extended into theAstor valley, the glacier from the Rupal valley must haveadvanced considerably. It appears most likely that thiswas at a time in the Pleistocene when temperatures weresu$ciently low to support such a large ice mass at suchrelatively low altitudes. The weathering state of the surfa-ces of the large boulders (post-maximal), by analogy withthe Hunza valley (Derbyshire et al., 1984), suggests an ageperhaps as old as the Middle Pleistocene. The evidence ofextensive and intense erosion and reworking of gla-ciogenic debris from valley side locations to the valley#oor is also consistent with such an age estimate.

As well as the valley side deposits, accumulations ofdiamictons exist as a hummocky, chaotic assemblage oflow mounds and depressions across the #oor of themiddle Astor valley. Their hummocky topography givesthe appearance of till produced by local glacial stagna-tion (Hoppe, 1952; Benn, 1990). In some places thesepoorly sorted deposits are visible in sections resultingfrom dissection by the Astor River.

In these sections, the identi"cation of boulder beds(formed by the depletion of "ne matrix), small scale andlocalized strati"cation of deposits, depletion of "nes andalso accumulation of "nes suggest that this material isa meltout till. The deposits are generally massive witha sandy matrix (Fig. 4B), but with many localized areas of


Table 1Microfabric for glacial and non-glacial diamicton in Nanga Parbat study areas

Sample location Shearing Strati"cation Packing Fabric Grain features

Kine Das highterrace meltout till

Pseudoshears *irregular orientation

None Open, localizedcompact zones

Di!use

Kine Das lowterrace meltout till

Pseudoshears *irregular orientation

Localized micro-lamines of sift

Open, localizedcompact zones

Di!use

Gehrak till Localized pseudoshears None Open, localizedcompact zones

Di!use

Gehrak debris#ow

Widespread-downslope dip

Present in parallelto debris surface

Open and porous Di!use

Astor valleyhummocky till

Many irregularpseudoshears

Localized micro-lamines of sift


Di!use some verticallydisposed silts

Rampur basaltill

Widespread withup-valley dip

Pseudolaminae-aligned with shears

Overconsolidated,localized open zones

High grainanisotrophy

Localisedbridges ofcemented grains

Churit basal till Widespread withup-valley dip

Pseudolaminae-aligned with shears

Overconsolidated,localized open zones

High grainanisotrophy

Edge crushingof grains

Churit meltouttill

Pseudoshears * irregularorientation, subvertical

None Open, localizedcompact zones

Di!use Edge crushingof grains

Tarshing meltouttill

Pseudoshears * irregularorientation and dip

Microlaminae,some deformed


Di!use

Tato high terracemeltout till

Pseudoshears * irregularorientation and dip



Di!use Localisedbridges ofcementedgrains

Tato hummockytill

Pseudoshears * subverticaland irregular orientation



Di!use, some verticallydisposed silts

Fugtoury meltouttill

Irregular pseudoshears& some down-valleyshear structures

Microlaminaeof silt



Localisedbridges ofcemented grains

Astor meltout till Irregular pseudoshears& some down-valleyshear structures

Microlaminaeof silt,some deformed


Di!use

Rama terrace 1meltout till





Rama terrace 2meltout till





Fig. 5. Section through a debris fan at Gehrak in the middle Astor valley showing a glacial deposit at its base and particle size results for samples A}D.The locations of samples A}D are shown on the section. Lithofacies codes after Eyles et al. (1983).


Fig. 6. Section through a hummock on the #oor of the middle Astorvalley. Lithofacies codes after Eyles et al. (1983) (Dmm * massivematrix-supported diamicton; Dms * strati"ed matrix-supported dia-micton; Dcm * massive clast-supported diamicton; Dcs * strati"edclast-supported diamicton).

Fig. 7. Geomorphological map of the Rupal valley.

"nes depletion or accumulation, as shown in Fig. 6. Atthe microscopic scale, the fabric appears to be di!usewith large numbers of pseudoshears having many di!er-ent orientations and dips (Table 1). This evidence sup-ports the initial identi"cation of the material as a meltouttill (Owen, 1991), but suggests that it has been subjectedto widespread resedimentation during deposition be-cause of the highly localized internal strati"cation andsorting within an otherwise massive diamicton (Haldor-sen and Shaw, 1982). These hummocky tills are thusconsidered to be the product of ice wastage during the"nal glacial retreat up the Astor valley.

Following the retreat of the ice, non-glacial geomor-phological processes reworked and resedimented manyof the glacial deposits, incorporating them within debrisfans and other slope deposits, and in some places almost

completely removing them. Evidence for resedimentationand redeposition from the valley side benches down tothe valley #oor in the form of debris #ows and slides iswidespread, some benches being surrounded by a drapeof redeposited material (e.g. at Astor). The redepositedmaterial is similar to the deposits found on the benches inrespect of particle size, clast lithology and degree of clastweathering and edge rounding. However, its directionalfabric exhibits a marked di!erence, as it has a well-developed mean dip towards the valley #oor, and a meanorientation at right angles to the main valley in which itwas redeposited.

4. Rupal valley

The Rupal valley runs along the south side of themassif (Figs. 2 and 7). There are several glaciers in itstributary valleys to the north, and the Rupal glacier liesat its head, some 24 km up-valley. Large accumulationsof both glacial and non-glacial sediments have been ex-posed by downcutting of the Rupal River. Four mor-phostratigraphic units have been recognised in the formof terraces Tl to T4, and at least four distinct sedimentaryunits can be identi"ed. Fig. 8 summarizes the evidence forthese morphostratigraphic and sedimentary units, ob-served along sections from Tarshing to the easternmostend of the valley. Each terrace will be described in turn.

4.1. Rampur terrace (¹1)

At the base of the terrace at Rampur, 2 to 6 m abovethe present river level, an overconsolidated and poorly


Fig. 8. (A) Longitudinal pro"le and deposits of the Rupal valley between Tarshing and Rampur, (B) vertical sedimentary pro"les through diamictondeposits in the Rupal valley. Lithofacies codes after Eyles et al. (1983) (Dmm * massive matrix-supported diamicton; Dms * strati"ed matrix-supported diamicton; Dcm* massive clast-supported diamicton; Dcs* strati"ed clast-supported diamicton; Fl * silts with "ne lamination oftenwith minor "ne sand and very small ripples; Sg* sand with graded bedding; Sh* sand with horizontal planar bedding; Gt* gravels with troughcross-bedding; (r) * evidence of resedimentation; (s) * sheared).

sorted material of uncertain thickness is present (Fig. 8).It contains a high proportion of sub-rounded clasts andappears to have a much "ner matrix than any otherdeposits exposed in the sediment series. Localized shear-ing can be observed. On the basis of these textural char-acteristics, the rounded shape of its clasts and its positionat the base of the sediment series, this material wasclassi"ed in the "eld as a basal deformation till. SEMobservation revealed shearing of the tightly packedmatrix and edge crushing of single particles (Table 1) alsoconsistent with a subglacial origin (Owen, 1991). Particlesize analysis showed it to be far "ner than any of theother samples collected from this valley (Fig. 9), the highsilt content being characteristic of deformation and/orlodgement till. This deformation till was probably laid

down during a period when the Rupal glacier was moreextensive than at present.

Above the deformation till, massive units of poorlysorted diamicton are present down the length of theRampur terrace, varying in thickness between 35 and70 m (Fig. 8). These were interpreted in the "eld as tillsassociated with ice wastage up-valley, an interpretationbased on the presence of some edge-rounding of the largesubangular clasts and the "nes-rich matrix supportingthese clasts. At the lower end of the valley, localizedboulder beds exhibiting crude and sub-horizontal bed-ding are widespread within the glacial diamicton and, toa lesser extent, localized sand bodies are also present. Thesand bodies can be seen in the upper 10 to 20 m of thevertical pro"le of the Rampur deposits shown in Fig. 8B.


Fig. 9. Particle size distribution envelopes for glacial deposits in theRupal valley.

Fig. 10. Relative dating of terraces and moraines along the Rupalvalley between Tarshing and Rampur.

Sorting of material was interpreted in the "eld as evi-dence of large scale reworking of the till, following icewastage. Samples of matrix were collected from the tillsfor particle size and microfabric analysis. The results ofthe particle size analysis (Fig. 9) show the reworked tillsto be coarse and generally depleted of "nes, with con-siderable grain size variability. The clasts within theboulder beds show the best developed fabrics. This com-bination of characteristics suggests #uvial reworking.

The top 5 to 10 m of the valley sections at the lowerend of the Rampur terrace, as shown at the top of theRampur vertical pro"le in Fig. 8B, contain colluvialdeposits derived from the valley sides. These are poorlysorted diamictons with a "ne-grained matrix. They canbe distinguished from the glacially derived materials,however, on the basis of their distinct surface morpho-logy. This consists of debris fans and #ows from thevalley sides, the contained clasts being angular and sub-angular, and their directional properties being consistent(Owen and Derbyshire, 1989). Debris #ows in this regionhave well de"ned leveed channels at the surface anda clearly bedded internal structure, with dips parallel tothe depositional slope (Owen, 1988). Clasts within the

debris #ows tend to be more angular than glacially de-rived clasts, with little evidence of edge rounding. Thesedistinctions become less valid where debris #ows andother slope processes incorporate glacially derived ma-terials, but, in most cases, they served to discriminate theglacial from the non-glacial diamictons.

Relative dating of the clasts on the surface of thesereworked tills using the rock varnish index method, aswell as percentages of split and pitted clasts, indicatesthat they are more weathered, and so may be older thanany tills further up the valley (Fig. 10). The similarity inclast weathering values for the tills below Churit andRampur suggest that they are of similar age, and that thestagnation period resulting in their deposition wasbroadly synchronous.


4.2. Churit and Zaipur terraces (¹2)

These terraces comprise the most extensive valley-"llunit in the Rupal valley, stretching for 1.3 km down-valley and having thicknesses of between 50 and 100 m(Fig. 8A). In the "eld this unit was classi"ed as a predomi-nantly glacial diamicton, with colluvial deposits at itssurface, as shown in the vertical pro"les C and D inFig. 8B. At its base is an overconsolidated and poorlysorted material, containing sub-rounded clasts in a "nes-rich matrix (less extensive but similar to that identi"ed asa deformation till in the Rampur unit). Localized evi-dence of shearing within this diamicton is shown at thebase of the vertical pro"le D in Fig. 8B. On the basis of its"eld characteristics, this material is also classi"ed asa basal deformation till. Its particle size is texturallysimilar to the basal tills at Rampur (Fig. 9), and the highsilt content is characteristic of a basal till (Boulton, 1978).The microfabric of this deposit has a tightly packed andoverconsolidated matrix, with some localized dilationjoints (Table 1), both being recognized features of lodge-ment tills (Owen, 1991). These results support a sub-glacial origin for this till. It is suggested that it isa product of the same glacial advance that produced thebasal deposits at Rampur.

A massive and poorly sorted glacial diamicton be-tween 50 and 90 m thick is present above the previouslydescribed sediment (pro"les C and D in Fig. 8B). Itcontains large angular clasts in a "nes-rich matrix, theclasts showing signs of edge rounding. Sorting ofmaterial appears to be highly localized with somesmall boulder beds and pockets of "nes-rich sedimentsrevealed in the sections. Particle size analysis of samplesof the matrix con"rms its uniformly massive nature.Observation of the microfabric using the SEM providesresults in accord with this, with many irregular`pseudoshearsa and deformed laminations being present(Table 1), indicating irregular settling of material (Owen,1991).

At the lower (eastern) end of both the Churit andZaipur terraces, the surface drops steeply down to theRampur terrace, as shown by the vertical and convexbreaks in slope in Fig. 7. At the downstream end of theZaipur terrace this decline in surface elevation is step-like. Down-valley of these steps, the end of the Zaipurunit contains a strati"ed bouldery diamicton exposedwithin the uppermost 5 to 10 m of the meltout till (pro"leE in Fig. 8B). These boulders are found more than 1 kmdownstream of the Zaipur unit. These deposits evidenceof bedding and the "ne matrix has been depleted (Fig.8B), evidence consistent with #uvial activity across thesurface of the meltout deposits immediately belowChurit. Together with the large increase in terrace heightacross the valley at Churit and Zaipur, this suggests thata still-stand took place near to Churit and Zaipur duringglacier retreat.

Colluvial deposits, 5}8 m thick, derived from the valleysides, occur at the top of the Churit and Zaipur terraces,as shown at the top of vertical pro"les C and D in Fig.8B. These were distinguished in the "eld on the basis ofthe angularity of the contained clasts, and obvious bed-ding with dips parallel to the depositional slope (e.g. deJong and Rappol, 1983; Owen and Derbyshire, 1989).

Relative dating of the clasts on the surface of themeltout tills shows that the Churit and Zaipur tills havesimilar degrees of surface weathering. However, the clastslower down the valley are slightly more weathered thatthose towards the head of the valley. This slight down-valley increase in relative weathering in the tills can beseen in Fig. 10. The similarity of the weathering valueswithin the Churit and Zaipur tills suggests that the epi-sode of stagnation during which these deposits formedwas one of extensive, general down-wasting. Fig. 10 alsoshows that the clasts of the Churit and Zaipur tills appearto be less weathered than those down-valley at Rampur,but more weathered than those up-valley at Tarshing.These results are in agreement with the interpretation ofthese deposits as meltout tills lain down during a generalglacier retreat.

4.3. Tarshing terrace (¹3)

This distinct terrace is present above the Churit andZaipur terraces. It is 0.8 km in length and up to 110 mthick (Fig. 7). It appears to have sedimentary character-istics similar to the meltout deposits identi"ed at Churit,being a massive glacial diamicton with a "ne matrixcontaining large angular clasts with sub-rounded edges(Fig. 8B). The particle size distribution envelopes for thematrix samples from Tarshing shown in Fig. 9B aresimilar to the envelopes for the matrix samples from theChurit meltout till shown in Fig. 9A. Some localized"nes-rich deposits and boulder beds are present in theTarshing deposits. The directional fabric of the boulderbeds indicates local resedimentation (cf. Dowdeswell et al.,1985). The microfabric of this material is directionallydi!use (Table 1), which is another characteristic indica-tive of meltout till (Owen, 1991). Fabric analysis fromtwo well sorted deposits within the main body of the tillindicate strong localized orientations and dips, sugges-ting that these are localized mass movement deposits(Lawson, 1979a, b; Owen, 1991). These results supportthe "eld identi"cation of this diamicton as a till formedby meltout and subject to resedimentation by localizedmass movement. Relative dating measures applied to theTarshing unit show that all materials within it are ofa similar age, with the clasts having a consistent degree ofweathering throughout (Fig. 10). This degree of weather-ing is less than that seen in the tills down valley, so thatthe Tarshing unit is probably younger than both theChurit and Rampur units, having been formed by a dis-tinct and more recent period of meltout.


Fig. 11. Vertical exposure through Nahake terrace in the Rupal valley.

Evidence for a second glacial still-stand is also presentat Nahake, at the downstream end of the Tarshing ter-race. Here, "ne lacustrine sediments, strati"ed sand de-posits and channel "lls occur, within the top 10 m of themeltout till (Fig. 11). A vertical pro"le through thesedeposits (Fig. 8B) shows the interstrati"cation of theserelatively thin (0.5}4 m thick) deposits at the top of themassive till unit. These well-sorted deposits were classi-"ed in the "eld as glacio#uvial in origin. They indicateconsiderable glacio#uvial activity in an active proglacialenvironment, subsequent to the deposition of the sub-jacent tills. The repeated interstrati"cation of glacial dia-micton and waterlain sediments implies sedimentation inan ice-marginal setting (Boulton, 1977) and thus theglacier snout must have been close to Nahake. Somesediment sequences within channel "lls are almost 4 mthick. A period of glacier front stability appears to haveoccurred close to Nahake and may represent a still-standduring glacier recession, although no evidence of thelength of such a still-stand is available.

Active slope processes in the current non-glacial envi-ronment have deposited colluvial materials from the val-ley sides at the top of the Tarshing and Nahake units, ascan be seen in the upper part of vertical pro"les A andB in Fig. 8B. These have the distinctive surface morpho-logy and sedimentary characteristics (for example, coarseand variable grain size distributions and angular shapedclasts) indicative of debris #ow deposits (de Jong andRappol, 1983; Owen, 1991).

4.4. Lateral moraine ridges (¹4)

A series of prominent lateral moraines is presentaround the present margin of the Chungphar glacier,

with distinct ridge forms that appear to be superimposedupon the Tarshing meltout till terrace (Fig. 7). Relativedating of the moraines shows that the clasts on the innerlateral are less weathered, and therefore younger, thanthose of the outer lateral moraines (Fig. 10). These rela-tive ages are con"rmed by the fact that erosion andresedimentation of material on the crests of the outermoraines are greater than those found on the inner. Rockvarnish on boulders in these moraines is very poorlydeveloped, suggesting that these deposits are theyoungest in the valley. This degree of rock varnish devel-opment is comparable to that found on Holocene de-posits in the adjacent Karakoram region (Derbyshireet al., 1984) and the age of these moraines may, therefore,be reasonably assigned to the Holocene.

In summary, it is apparent that all of the glacial de-posits examined in the Rupal valley were laid downduring the wastage and retreat of the Rupal glacier to itspresent position. Fig. 12 shows a four-phase model forthe development of the observed sedimentary sequences.In this model, the retreat of the Rupal glacier up-valleyproduces the meltout tills which form the Rampur ter-race (Stage I). A still-stand in this retreat occurs at Churitto produce a change in surface topography, with meltouttills forming in an ice-contact position at Churit andglacial meltwater reworking the Rampur tills (Stage II).Further glacier retreat to Nahake produces meltout tillswhich form the Churit and Zaipur terraces, with a sub-sequent still-stand at Nahake producing glacio#uvialsediments (Stage III). Further glacier retreat, fromNahake, produces meltout tills at Tarshing which form inan ice contact position (Stage IV). The distinct changesin surface morphology down the Rupal valley, alongwith the glacio#uvial sediment features, suggest two


Fig. 12. Schematic development for the deposits in Rupal valley: (I)Glacier retreat up-valley produces meltout tills. (II) Still-stand atChurit, Rampur tills are reworked by glacier meltwater. Meltout tillsform in ice-contact position at Churit. (III) Glacier retreat to still-standat Nahake produces meltout tills along valley. Glacio#uvial sedimentsaccumulate at Nahake. (IV) Glacier retreat forms meltout till at Tarsh-ing. Colluvial diamictons deposited from valley sides down the length ofthe valley.

still-stands during glacier retreat, the "rst being at Churitand the second at Nahake. Available evidence is insu$-cient to demonstrate whether the stages in sedimentaccumulation represent still-stands punctuating a gen-eral glacial retreat or short-term advances of the glacier.However, the evidence presented, implying synchronousice wastage within each terrace unit, suggests that a pro-cess of ice wastage and retreat punctuated by still-standsis more probable.

5. Rakhiot valley

The upper part of the Rakhiot valley has truncatedspurs, hanging valleys, steep valley sides and an over-deepened trunk valley indicating that glacier levels atsome time in the past must have been at least 650 mhigher than those of the present day. Trimlines of thisearlier glaciation cannot be identi"ed easily because thecontemporary slope processes have resulted in a wide-spread covering of scree and slope debris (Fig. 13). The

narrow river gorge, with its precipitous slopes beginning2 km north of Tato, retains no evidence of either a high-level surface or of till deposits. However, evidence oflarge-scale glacial activity in the past occurs in the formof tills, traceable along the valley to a point 1.5 km northof Tato (Fig. 13). These can be divided into four mor-phologically distinct units termed Tl and T2 at Tato, T3at Fugtoury and T4 at Bael.

5.1. Tato high terrace (¹1)

This accumulation of glacial diamictons, 200 m abovethe valley #oor, represents the most northerly evidencefor glaciation in the Rakhiot valley. The deposits occur asa narrow unit extending over a distance of 2.5 km (Fig.13). On the basis of their poor sorting, their large angularclasts with signs of edge rounding and their "ne matrix,these deposits were classi"ed in the "eld as glacial dia-mictons. They are dissected at their down-valley limitand there is evidence of extensive erosion in the form ofearth columns along their exposed faces. Localized boul-der beds occur within these massive units. There is somewith crude down-valley strati"cation, with interstrati"edpockets of "nes-depleted gravel. Particle size (Fig. 14)and microfabric analysis revealed that, whilst the major-ity of this till is massive and poorly sorted, there arelocalized areas of "ne sediment depletion and accumula-tion (Fig. 14). These characteristics are similar to the ice-contact fan deposits of Owen and Derbyshire (1989) inthe Karakoram region, the localized sorting being evi-dence of glacio#uvial activity and the fabric being in accordwith sediment deposition by meltout and mass movementprocesses (Owen, 1991). Thus, this deposit is interpretedas an ice-contact diamicton which must have been depos-ited at a time when the glacier terminus lay at Tato.

5.2. Lower Tato unit (¹2)

On the Rakhiot valley #oor there are thick hummockydiamictons dissected by the Rakhiot River that have theappearance of a till produced by local glacial stagnation.They are poorly sorted and contain large angular andsub-angular clasts with signs of edge rounding withina "ne-grained matrix. There are localized concentrationsof large clasts and some "nes-rich pockets (observed inthe river sections). This is consistent with classi"cation ofthis deposit as a meltout till (Haldorsen and Shaw, 1982;Derbyshire et al., 1985). Particle size analyses show thedeposits to be texturally massive, similar particle sizedistributions pertaining throughout the unit (Fig. 14).This is probably a meltout till similar to those describedby Owen (1991) in the Karakoram Mountains.

The degree of weathering of the surfaces of the largeclasts within both these units at Tato indicates similaradvanced stages of weathering, with the boulders dis-playing post-maximal rock varnish and high percentages


Fig. 13. Geomorphological map of the Rakhiot valley.

Fig. 14. Particle size distribution envelopes for glacial deposits in theRakhiot valley.

of pitting and splitting (Fig. 15). This suggests that theseunits are of comparable age, being the oldest glacialdeposits in the Rakhiot Valley.

5.3. Fugtoury terrace (¹3)

This unit is situated 2 km south and upstream of Tatowhere it forms a distinct high terrace, 250 m above thevalley #oor (Fig. 13). It extends part of the way across thevalley but is dissected by the Rakhiot River to producesteep cli!s with earth columns. It appears to be com-posed entirely of glacial material as it is poorly sorted,and contains angular clasts up to 2 m in length withina "nes-rich matrix.

Localized boulder beds up to 5 m in length, exhibitingcrude down-slope strati"cation, are exposed in the earthcolumn cli!s throughout the unit. Localized strati"ed

sandy deposits are also present and these were inter-preted in the "eld on the basis of their well-sorted andbedded structures as being low-energy glacio#uvial sedi-ments. The sediment is texturally massive and poorlysorted. Where strati"cation exists it is locally variable,with clast fabrics subparallel to it, strongly suggestingthat this is an ice-contact deposit. As such, it was laiddown when the ice front was close to Fugtoury.

Relative dating measures were applied to the largerclasts at the surface of this unit. The strong brown rockvarnish, and the degree of splitting and pitting of boul-ders (Fig. 15) are similar throughout the whole unit,indicating that all deposits within the unit are of similarage. The degree of weathering of the boulders is markedlyless than those observed around Tato. For this reason,the Fugtoury terrace is considered to be younger than theTato units, and thus represent a distinct stage of glacialdeposition following retreat of the ice from Tato. As inthe Tarshing valley, the available evidence is not su$-cient to show whether the Fugtoury terrace was formedduring a readvance of the glacier or by a still-standpunctuating general glacial retreat.

5.4. Bael unit (¹4)

This unit exists on both sides of the valley as a "llbetween the glacier and the valley sides. It appears in the"eld to be composed of glacial material, overlain on thevalley sides by colluvial debris #ows. These debris #owdeposits have distinctive morphologies, with channelsand levees descending from the valley slopes to form fanson the surface of the glacial material (Fig. 13). The dia-micton was classi"ed as glacial in the "eld on the basis ofits poorly sorted texture with large angular clasts sup-ported in a "ne matrix. The clasts are less angular than


Fig. 15. Relative dating of terraces and moraines along the Rakhiot valley between Bael and Tato.

those of the debris #ow deposits. Particle size analysis ofsamples of matrix from within the till con"rmed it to betexturally massive with a rather narrow size distribution.Relative dating measures were applied to the clasts onthe surface of this lateral moraine, down the length of theunit. The results shown in Fig. 15 indicate that theseclasts are in the same weathering state throughout thedeposit, suggesting that this lateral moraine is all of oneage. These results also suggest that the moraine isyounger that the glacial deposits at Fugtoury and Tato(Fig. 15).

5.5. Contemporary lateral moraines (¹5)

Large, clearly de"ned lateral moraines extend allaround the present Rakhiot Glacier margin as an insetsequence paralleling the glacier. This clearly de"ned mo-rainic series suggests an episodic retreat of the glacier.The clasts within the moraine are angular and are con-tained within a "nes-rich matrix. Post-depositionalweathering and reworking of the outer lateral moraineshas reduced their formerly sharp crests to low, roundedridges. Large clasts on the surface of these outer morainesexhibit a moderate pale brown rock varnish, whilst thoseof the inner moraines have a slight pale yellow varnishconsistent with the fact that they are among the youngestglacial deposits in the Rakhiot valley.

In summary, the available evidence from the Rakhiotvalley suggests that the deposits are the product of twodistinct periods of relative stability of the glacier terminusduring its recession: at Tato and Fugtoury. A schematic

model of the development of the observed sedimentarysequences, incorporating two still-stands during retreat,is shown in Fig. 16. Stage I of this model represents thestill-stand of the glacier at Tato with characteristic ice-contact material. Stage II shows glacier retreat producingmeltout tills from ice wastage along the valley #oor untilthe next still-stand at Fugtoury where ice-contact mater-ial again accumulated. Further ice wastage in stage IIIoccurred until the glacier reached its present position,large lateral moraines being associated with punctu-ations in the general retreat. It must be reiterated, how-ever, that the observed evidence does not allow a cleardistinction to be made between two still-stand positionsor two short but distinct advances.

6. Rama valley

The Rama valley trends NE}SW with the Sachenglacier at its head. Three main terraces are present(Fig. 17) and will be described in detail.

6.1. The astor terrace (¹1)

At Astor, in the lower part of the valley, a cone shapeddeposit 1.5 km across at its lower end, 1.5 km in lengthand over 250 m thick, rises above the Astor valley #oor.This was interpreted in the "eld as a glacial depositformed in an ice-contact position, as it could be seen toexhibit features described in such deposits by previousworkers (Owen and Derbyshire, 1989). These include


Fig. 16. Schematic development of Rakhiot valley. (I) Still-stand of ice at Tato gives rise to accumulation of ice-contact material at northern end ofvalley. (II) Glacier retreat up-valley to Fugtoury produces meltout deposits along valley #oor, second still-stand gives rise to accumulation ofice-contact material at Fugtoury. (III) Further glacier retreat up-valley punctuated by minor still-stand/readvances producing large lateral moraines.Deposits dissected by Rakhiot glacier meltwater.

Fig. 17. Geomorphological map of Rama valley.

massive and crudely (meter-thick) strati"ed diamictoninterstrati"ed with glacio#uvial sands and gravels(Fig. 18). The diamictons contain large angular clastswithin a "nes-rich matrix. Particle size analysis shows theglacial diamicton to be generally massive in texture,but with localized areas in which grain size is very vari-able (Fig. 19). Microfabric analysis of the matrix showsthe di!use nature of the fabric with localized areas ofstrong orientation (Table 1). These characteristics areconsistent with an ice-contact origin for these fans. Assuch, they mark a former ice terminus in the vicinity ofAstor.

6.2. Rama terrace levels (¹2) and (¹3)

Up valley from Astor two distinct terrace levels can beseen (Fig. 17). These appear to be composed of tills, beingpoorly sorted and containing large angular clasts set ina "ne matrix, characteristics consistent with an originfrom local ice wastage, associated with glacial retreat.Throughout these deposits, no signi"cant textural dis-tinctions were observed between the terrace units. Par-ticle size analysis revealed that the glacial sediments arevery similar throughout, but that material taken frombreaks in slope between the terrace levels (the base of the


Fig. 18. Vertical sedimentary logs through deposits of the Astor ice-contact fan. Lithofacies coding after Eyles et al. (1983). (Dmm* mass-ive matrix-supported diamicton; Dms * strati"ed matrix-supporteddiamicton; Dcm * massive clast-supported diamicton; Dcs * strat-i"ed clast-supported diamicton; Dmg* graded matrix-supported dia-micton; Fl* silts with "ne lamination often with minor "ne sand andvery small ripples; Sh * sand with horizontal planar bedding; Gt* gravels with trough cross-bedding; Gm * massive clast-supportedgravel; (r) * evidence of resedimentation; (s) * sheared).

Fig. 19. Particle size distribution envelopes for glacial deposits in theRama valley.

terrace risers) show greater variability than those withinthe terraces. At the microscopic scale, pseudoshears arepresent with highly variable orientations and dips(Table 1), features which are consistent with melt-out (Owen, 1991) and typical of ice-front deposits(Derbyshire et al., 1985; Boulton, 1986). The lack of goodsections prevented further and more intensive investiga-tion of this series of glacial deposits. Around the presentterminus, a new terrace level can be seen in the process offormation as an end moraine, rising 50 m above the

Rama glacial terrace (Fig. 17). This ice-contact end mo-raine can be considered as an analogue of the Ramavalley terraces. The terraces probably formed by meltoutduring a glacier retreat which was punctuated by periodsof still-stand, during which ice-contact deposition wasconcentrated over a short valley reach. This sequence ofevents could well have produced the distinctive terracelevels which can be seen along the valley, the steep breaksin slope marking successive positions of the glacier snout.If this interpretation is correct, the Rama valley depositsprobably represent at least two periods of ice stagnation.

7. Discussions and conclusions

Evidence from the Nanga Parbat region as a wholeindicates that, at one or more times in the Pleistocene, anextensive glacier system occupied the valleys of the massifwith ice fronts more than 15 km down-valley of theirpresent positions. The only "rm evidence of distinctPleistocene glacial advances lies in the glacial landformsof the Astor valley where two separate glacial advancestook place. Extension of ice into this valley would haverequired a substantial lowering of regional temperaturesin line with Pleistocene events in other parts of thenorthwest Himalaya. Elsewhere in the massif, glacialevidence suggests less extensive glaciation with snoutpositions no more than 12 km beyond those of the pres-ent. Although it appears that the depositional evidence ofearlier Pleistocene glaciations in these high valleys hasbeen destroyed by subsequent glacial and slope activity,erosional evidence of extensive glaciation in the form oftruncated spurs, hanging valleys, steep valley sides andover-deepened trunk valleys is present. Trimline evidenceis vague because of the intense slope processes that havepersisted to the present day.

The evidence presented in this study clearly shows thatthe deposits present in the high valleys of the NangaParbat Massif mark a waning series of glacier fronts, theglaciers becoming more topographically constrainedwith time, leading to the present extreme example of thisstate. Distinct ice front accumulations, marking eitherstill-stands or pulsed advances, are clear in the glacialdeposits within the high valleys. The intermediate glacialdeposits owe their origin to glacier stagnation and down-wasting. In all valleys the lowermost deposits mark theoutermost ice-front position and thus are the oldest.A comparison between the relative dating results fromthe Rupal and Rakhiot valleys, which lie opposite sides ofthe Nanga Parbat summit, suggests a broadly syn-chronous series of events of regional status. The clastswithin the lowest (oldest) glacial deposits appear to ex-hibit similar degrees of weathering and thus it can bereasonably inferred that they are of a similar age. Wast-age of the glaciers up-valley can be seen in all cases tohave been punctuated by at least two still-stands or


Fig. 20. Proposed ice extents during the late Quaternary for the NangaParbat massif.

readvances in each valley system followed by furtherglacier retreat. The lack of unequivocal evidence of gla-cier advances during general retreat may render still-stand the more likely explanation. Clasts within theextensive meltout tills formed during wastage eventsshow similar degrees of weathering throughout. Thissuggests that retreat between stages were relatively rapid.In contrast, the thickness of the still-stand deposits sug-gests that these periods were relatively lengthy, or thatthe glaciers contained large volumes of debris.

A tentative outline of Quaternary glaciation of theNanga Parbat Massif is shown in Fig. 20. Evidence fromthe Nanga Parbat glacial systems does not indicate thatglacial readvances took place at any stage followinga glacial maximum in the upper Pleistocene. Rather,glacial retreat from this maximum was merely punc-tuated by periods of still-stand. Such still-stands in gla-cial conditions could have been brought about by factorsother than reversal of the regional warming trend en-visaged for this region through the Quaternary (Kick,1980; Kalvoda, 1981). For example, increases in glacialaccumulation could result from increases in precipitationbrought about by a changing regional wind system, suchas #uctuations of the monsoon (Mayewski and Jeschkte,1979; Holmes, 1988). Also, uplift in the form of tectonismor isostatic rebound could increase glacial accumulationby the promotion of orographic rainfall (Molnar and

England, 1990) and provision of more topographicallye$cient accumulation areas. Such changes in glacier ac-cumulation might well prove su$cient to bring abouta standstill in the wastage of ice. Not until the sedimen-tary sequences in the valleys of regions such as the NangaParbat Massif are rigorously dated will it be possible touse them to improve understanding of the interactionbetween uplift and climatically driven glacial changes.

The timing of glaciation throughout the Nanga ParbatMassif has still to be adequately resolved. Sloan et al.(1998) applied the cosmogenic 3He surface exposure tech-nique to garnets in moraine boulders in the Rakhiotvalley. These gave tentative dates for the oldest morainesof &56 ka and a younger set of moraines at &8 ka.Furthermore, using optically stimulated luminescencemethods Richards et al. (2000a) dated glaciogenic sedi-ments in the middle Indus valley, the Swat Himalaya andthe Rampur valley. These show that several glaciationsoccurred during the last glacial cycle with the maximumadvance during oxygen Isotope Stage 3 (Fig. 1a). Thedates on the Rampur moraines showed that ice stilloccupied the Tarshing valley at 15.1$4.4 ka. These datasupport the view that the maximum extent of glaciationin Nanga Parbat occurred during the early part of thelast glacial cycle. At least two readvances or periods ofstagnation during late Pleistocene times, and at leastthree limited advances during the Holocene followed thelocal Last Glacial Maximum.

It is reasonable to assume that, since the end of thePleistocene, a signi"cant change in the glacial extent andregime in Nanga Parbat has taken place, from one erod-ing mostly subglacially to one in which supraglacialdebris is dominant. Evidence indicating such a shift canbe seen throughout the Nanga Parbat Massif where thebroad valleys with their steep valley sides and truncatedspurs can be ascribed directly to erosion by extensive,thick glaciers in the late Pleistocene. Following theirwastage, the voluminous glacial deposits in the valleysprovide evidence of a greatly increased input of supra-glacial debris, and a comparative decline in the subglacialcomponent of the system. This evidence shows that withthe end of the Pleistocene, there occurred both a changein glacial extent and a change in the type of glacial systemoperating in this region.

Acknowledgements

Thanks go to the NERC (Award GT4/89/GS/053) forfunding this research and Kim Li for drafting the "gures.

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