RESUME OF GEOLOGICAL RESULTS, SHAKSGAM EXPEDITION, 1937

J. B. Auden

The area described in this account¹ occupies about 2,000 square miles and is situated on both sides of the Karakoram range, extending northwards up to the Yarkand river at approximately latitude 36° 22' N. It is included partly within the provisional issues of Survey of India J-inch maps 42 p, 43 m, and 52 a. Most of our time was spent in the area covered by the as yet unpublished map 51 d. The visit was made in the company of E. Shipton (leader), H. W. Tilman, and M. A. Spender. I wish to record my thanks to Shipton for the invitation to join his expedition and for the well- planned arrangements that were made throughout. Spender and I had little of the worry connected with coolies and the distribution of food supplies, and were spared the monotony of relaying, which Shipton and Tilman unselfishly supervised. Moreover, when mountaineering difficulties did occur, if was often their experience and skill which allowed us to carry out our programme.

It is true that geological work would have been easier and more detailed if I could have been relieved of carrying a rucksack loaded with personal and survey equipment, and had there been no necessity of keeping rigidly to a time-table. For reasons of economy, however, it was imperative to cut down the porters to the absolute minimum, and the rapid flooding of the rivers in July necessitated our being on the Indian side of the Shaksgam by a settled date. The flooding of the rivers, both daily in the afternoons, and seasonal as the summer progressed, became for us the chief bogy. Indeed, it was a fortunate spell of cloudy and snowy weather at the beginning of July which, by lessening the melting of the glaciers and lowering the Shaksgam, allowed us ever to return across this river. When I reached the Shaksgam with Lhakpa and Mahadi on the 28th June, after crossing the Aghil col, we were somewhat dismayed at the expanse of water, and had fears of all of us having to go north again, over the Aghil pass, with food exhausted, and the prospect of an uncertain welcome by Yarkandis below Bazar Dara.

Apart from the reconnaissance map of Professor Desio, which included the Panmah and Sarpo Laggo valleys and part of the Shaksgam, there were no topographical data upon which to base a geological map. Geological sketch plans were made throughout the expedition, and it is hoped to adapt these to the topographical map on which Spender has been working since our return. Spender tirelessly carried out the main survey, based on K² peak, 28,250 feet, while Shipton and I used a light 3-inch theodolite, belonging to the Royal Geographical Society and fitted with a Leica photographic attachment, to fill in details of areas he was not able to visit. These included the K² glacier, surveyed by Shipton, and the lower Shaksgam valley and Nobande Sobande glacier, done by myself. Spender has the more difficult and exacting task of incorporating these results in the general map.

 

Geological notes of the area south of the Karakoram watershed were made by Godwin Austin in 1861, by Lydekker in 1883, by Dainelli in 1913, and by Desio in 1929. Desio was the only geologist who had worked north of the watershed. Hayden visited the Pamirs in 1914, and De Terra examined the Depsang area in 1928. On a previous expedition to the Biafo glacier in 1933 I was able to make observations which supplement those collected this year.¹

Before coming to the geological results obtained this year it is necessary briefly to refer to the works of Lydekker, Hayden, and Desio. Lydekker published two papers, in the first of which there is a map on the scale of 8 miles to 1 inch, including details of the Biafo area.² In this map he shows a synclinal band of Triassic rocks overlying newer gneiss, which in turn overlies older or central gneiss. This band of synclinally disposed Trias is shown running up the Biafo glacier, although Lydekker only saw the rocks at the snout. His examination of the area was cursory, and his published map shows extrapolations beyond the snouts of the Biafo, Panmah, and Baltoro glaciers which he actually visited. His older gneiss is probably the youngest rock of the district, being what I take to be an intrusive granite of Tertiary age. The marbles which he assigns to the Triassic are not synclinally disposed up the Biafo glacier, but are interbedded with biotite-schists and the structure is anticlinal.

Hayden³ traversed the Pamirs in 1914 and found an extensive series of Mesozoic limestones (called by him the Pamir limestone) overlying Sarikol shales and slates. He suspected that the Pamir limestone continued to the south-east towards the Raskam (Yar- kand) river.

Jurassic rocks were found in 1926 by the Mason expedition along the Lungmo-che and Sa Lungpa.

The most important work is that of Desio in 1929. Desio discovered fossiliferous Permo-Carboniferous rocks along the lower Sarpo Laggo and Shaksgam valleys, and made geological sketch maps of the Panmah, Baltoro, and Sarpo Laggo basins. He considered the metamorphic rocks of the Askole-Korofon area to be the altered equivalents of the fossiliferous rocks to the north. When I visited the Biafo glacier in 1933 I was inclined to doubt this correlation, and suggested that the metamorphic series was possibly equivalent to the Salkhala rocks of Archaean age described by Wadia. A wider experience of the area has led me to discard this view.

 

The sequences as shown in the sketch maps of the Panmah, Baltoro, and Sarpo Laggo glaciers (given respectively on pp. 157, 265, and 403 of Spedizione Geografica Italiana al Karakoram, Milan, 1936) are shown below, the correlations suggested being mine and not his. His geological results, published in Italian, are at present being translated for me, but it is assumed that Desio accepted the intrusive nature of the granitoid gneiss and granite, and that, in spite of their position at the base of the key, he does not consider these rocks to be the oldest in the region. Caution is required over this question. Desio¹ and Mason² speak of a granitic or gneissose 'basis' or 'core', but it is important to realize that this 'basis' is probably a batholith of intrusive granite, granodiorite, and gneissose rocks, and is not the basement upon which the sediments were laid down. In my view, the Shaksgam series were laid down upon the Sarpo Laggo rocks, and later both series were invaded by probably Tertiary batholiths. I may say that although Desio's sketch maps were not available to me until my arrival in England after the expedition, we are nevertheless in close agreement as to the geological disposition of the Panmah and Sarpo Laggo valleys.

Tables of sequences given by Desio

Panmah	Sarpo Laggo	Baltoro
		Conglomerates, breccias, and calcareous sand stones
Crystalline limestones	Permo-Trias fossiliferous limestones	Crystalline limestones
Black 'schists' with fene- stella	Conglomerates and cal careous sandstone with fusulina
Mica schists, gneiss, and crystalline limestones	Dark phyllitic schists	Phyllitic schists and phyllites
Plagioclase gneiss	Plagioclase gneiss	Plagioclase gneiss
Granitoid gneiss and granite	Granitoid gneiss and granite	Granitoid gneiss and granite

 

The results of this year's expedition have been to establish the existence of three main series, in descending order: the Aghil series (Triassic and Jurassic), the Shaksgam series (Permo-Carboniferous), and the Sarpo Laggo series (probably Lower Palaeozoic and older). Jurassic fossils have been found for the first time, and further collections have been made from the Permo-Carboniferous, supplementing those obtained in 1929 by Desio. These are at present in the hands of my colleague, Dr. M. R. Sahni, who hopes to make a detailed examination of them.

 

A comparison of the Pamir, Aghil-Shaksgam, and Depsang areas is given below:

In broad outline there is a zone of fossiliferous Tethys sediments which runs north of the Karakoram watershed from the Pamirs to the Rimo glacier, a distance of about 200 miles or 300 kilometres. This zone does not occur as a continuous outcrop, but appears to occur in a series of basins, possibly arranged en echelon and separated by the underlying unfossiliferous Lower Palaeozoic rocks. The length of the Mesozoic basin in the Aghil range west of the Aghil pass is about 16 miles or 26 kilometres. The next basin to the east appears to be situated along the Sa Lungpa and Lungmo-che valleys. In the area covered by our expedition, these older rocks crop out both to the south, along the upper Sarpo Laggo and Crevasse glacier valleys, and also northwards, along the Surukwat valley down to its confluence with the Yarkand river. There is no doubt that the Kun Lun range, on the north side of this river, is also to a considerable extent built up of Lower Palaeozoic and other rocks.

 

The area has been invaded by post-Carboniferous granodiorites, sometimes gneissose, and subsequently both granodiorites and sedi- mentaries have been injected by a network of lamprophyre dykes. These dykes are post-Triassic in age, since in one case an intrusion was found in the Megalodon limestone. Dolorites occur in the Aghil range, but their age, though post-Carboniferous, is not known in relation to the granitic rocks and lamprophyres.

In detail the structure is more difficult to understand. There are certainly recumbent folds of considerable dimensions in the meta- morphic rocks north of Korofon and in the Shaksgam series southeast of the Aghil pass, but these appear to be local and not to influence the structure on a regional scale. Moreover, while some of the granitic rocks are without question intrusive into the Permo- Carboniferous, there is one extensive contact, obliquely crossing the Aghil range, which suggests a faulted junction. East of the nala flowing south from the Aghil pass to join the Shaksgam river, the granite appears even to be overthrust upon the Shaksgam shales (36° 09': 76° 42').

A few points will now be discussed. First may be mentioned the question of metamorphism. Near the junction of the Sarpo Laggo and Shaksgam valleys there is an unaltered series of dark limestones and shales which belongs to the Permo-Trias series of the Aghil ranges. South of these rocks occurs intrusive granite in which there are found great vertical wedges of partially altered limestones, marmors, and slates. These wedges, with a visible height of 6,000 feet, are beautifully displayed along the sides of the K² glacier, from which they extend westwards across the Sarpo Laggo and Crevasse glacier valleys. By the K² glacier and towards the west the dark limestones lose their colour and turn more and more into white marmors. This is well seen up the Crown glacier, west of peak 23,829 feet, from the moraines of which fossiliferous (unidentifiable) ferruginous limestones were collected as well as partially transformed marbles. Desio found Fusulina in one of these wedges near the snout of the Sarpo Laggo glacier. The pelitic rocks remain more or less as slates. Turning southwards from the Crevasse glacier across the Karakoram watershed into the Panmah region, a syncline of marbles and pelitic rocks is crossed, with an east-west axis running along the Skamri range. The south limb of this syncline, which is seen above the Nobande Sobande glacier, contains rocks of the following types: coarse marbles, fine-grained biotite-schists, quartz-biotite-granulites and banded green calc-silicate hornfels, types which are common in the Askole area. The same pelitic rocks, which along the Crevasse glacier were in the form of slates, are to the south altered to biotite- granulites and schists. It was from a glacial moraine descending from the Skamri range and joining the Nobande Sobande near Drenmang that Desio found a specimen of Fenestella in black calc 'schists'. I put the word 'schists' in inverted commas because of the more elastic sense with which it is used by Continental writers. But even if the actual specimens containing Fenestella were slates and not schists, the important point remains that this fossil was found amongst the pelitic series, underlying the Skamri marbles, from a region where this series is for the most part metamorphosed to a schistose and granulitic condition. Still farther south, near Korofon, the metamorphism remains consistently at a higher level, with a coarser degree of crystallization, and with epidote, actinolite, diop- side, garnet, chloritoid, staurolite, andalusite, and kyanite as characteristic minerals. It seems to me indisputable that some of these highly altered rocks are Permo-Carboniferous in age. This was indicated by Desio, although the actual transitional stages along and south of the Crevasse glacier were not observed by him. It is concluded, therefore, that the unaltered rocks of the Tethys zone change southwards into a metamorphosed series of meso-grade type. It may be remarked that these metamorphic rocks are similar to those found in the Great Himalayan range between Harsil and Badrinath. This is not the place to discuss the rocks of the Himalaya, and similarity is often a dangerous guide, for the Archean rocks of the Peninsula also resemble the Himalayan and Karakoram meta- morphics. I have briefly mentioned this problem in an earlier paper.¹

De Terra claims that an unconformity exists between his meso- grade Karakash series and the over-lying epigrade Kilian series. There is no sign of an unconformity in the Karakoram area, where I am compelled to regard all the dark rocks underlying the Shaksgam series as belonging to the one Sarpo Laggo group. North of the Karakoram watershed the metamorphism of these rocks is generally low, phyllites with incipient biotite predominating over biotite-schists, and andalusite, chloritoid, and pin-head garnets being the chief porphyroblastic minerals. The equivalents of these rocks south of the watershed are probably to be seen in some of the biotite-schists found up the Biafo glacier, though in this region it has not been possible to separate the Shaksgam from the Sarpo Laggo series.

Even north of the watershed it is difficult to fix a definite boundary between the two series on account of the gradual oncoming of limestones in a shale and slate series. The presence of coarse conglomerates and breccias in the Shaksgam series indicates, however, an important change of conditions. Unfortunately, these conglomerates were found almost entirely as boulders and were only once seen in situ, in a wedge of rocks isolated in granite, so that its true stratigraphical position is obscure, although certainly Permo-Carboniferous. Fragments of carbonized wood were found in what is probably Shaksgam limestone just above the Aghil pass, a feature which, taken in conjunction with the conglomerates and the known presence of continental facies towards Yarkand, is of importance in indicating the proximity of a land mass. De Terra has described the continental Tisnab series, of Lower Carboniferous age, which he found in the Tisnab region (37⁰ 20': 77⁰). Similar red beds, perhaps of the same age, were seen this year crossing the Surukwat river and extending eastwards along the south bank of the Zug-Shaksgam from its confluence with the Surukwat. The Us nab series are very probably equivalent to the Nagthat series of Garhwal and the Tanol series of Kashmir. This continental facies has not been seen south of the northern Aghil ranges, and it would seem that there is a wedging out of continental rocks both northwards from Kashmir and southwards from Chinese Turkistan. There may have been a pronounced disconformity in the intervening area where these beds appear to be absent.

 

It is probable that the same diastrophism which resulted in Kashmir and Hazara in the deposition of Gondwana sediments also caused a southward enlargement of the Angara land-mass lying to the north. It was not until the end of the Carboniferous period that the Tethys sea finally extended over the whole region and marine conditions prevailed. Such conditions must have been shortlived in the north, because towards Yarkand there is also the Yarkand series, of continental type, and containing coal seams, which is of late Permian or early Triassic age.

The post-Carboniferous granodiorite intrusions of the Karakoram area strongly resemble those found along the Indus river and across the Deosai plains. Both series of granitic rocks are characterized by a considerable quantity of sodic plagioclase feldspar, the frequent presence of hornblende, and the abundance of xenoliths of basic rock. De Terra (XVI International Geological Congress, Washington) considered the Ladakh granite as having been intruded before the Indus Flysch was deposited, an assumption which would make the age of the granites pre-Upper Cretaceous. Yet the Dras-Burzil volcanic series are included as xenoliths within the Ladakh-Indus granite. Since the volcanics are probably early Tertiary in age, it follows that the granitic rocks should also be Tertiary. This is an anomaly that can only be elucidated by detailed mapping.

Finally, something may be said of the glaciers of this region. The great thickness of the ice during the period of maximum glaciation is a feature which is bound to impress all observers. Remnants of old moraines were found 2,700 feet above the snout of the Biafo glacier on the Laskam spur. North of the Karakoram watershed moraines were found up to a height of 1,200 feet above the valley floor on the spur between the K² glacier and the Sarpo Laggo valley. Formerly the glaciers must have extended far below the present positions of their snouts, both into the Shigar valley and for many miles down the Shaksgam below the Confluenza island, and were in some cases almost 3,000 feet thick.

Apart from this major secular retreat, there are also clear signs of the recent decrease in thickness of the ice near the snouts of the Biafo, Sarpo Laggo, and Crevasse glaciers. This loss in thickness amounts to some 150 feet on the Biafo glacier, to about 200 feet along the Sarpo Laggo, and 400 feet near the foot of the Crevasse glacier. This decrease in thickness is recent, but how recent is impossible to state on account of the paucity of accurate historical data. It is likely to have taken place within the last 100 years.

Of great interest is the still more recent periodic change in the nature of some of these glaciers. In 1929 Desio was able to walk up the,whole length of the Nobande Sobande glacier, and to use skis over its upper reaches. Desio's photographs show how smooth the ice was that year. In 1937 this glacier was so broken up into prisms of ice by gaping crevasses that it was impossible to get properly on to it, except within 5 miles of the snout where the moraine cover was extensive. Our route down from the 18,ooo-foot col over the Skamri range had to be along the left side of the glacier, sometimes in a narrow ablation valley, sometimes over rock cliffs overlooking the glacier, and once in a tunnel under the ice where it was pressed against an impassable rock wall. I have never before seen a glacier of such a gentle slope so crevassed and difficult to negotiate.

It is significant that Younghusband was unable in 1887 to proceed up the glacier beyond Skinmang on account of the broken condition of the ice. He states: 'There were great blocks of ice as big as houses tumbled about, one on top of the other, in such utter confusion that we could not get a footing on it at all.'¹ In 1922 Feather- stone reached Skinmang, but was forced to return on account of coolie trouble. He reports that the surface of the Panmah glacier was very uneven. The Choktoi branch of the Panmah did not seem this year to be nearly so cut up as the Nobande Sobande. Difficulties are, of course, relative. An alpinist experienced in ice-work might make light of conditions which others would find harassing. Without ¹ Proc. R.G.S., vol. x, 1888, p. 512.

making any claims to much experience of ice technique, I do, however, maintain that no party could have traversed along the Nobande Sobande this year between its confluence with our i8,ooo-foot col glacier and Skinmang, a distance of about 11 miles. Yet in 1929 it was smooth and easily accessible, a fact which is seen as well from Desio's photographs. It is assumed that this glacier was before 1929 and is at present in a state of degeneration, with gaping crevasses, and it is evident that the change is periodic.

In 1933 Gregory's orderly, Partab Singh, and I made a compass survey of the snout of the Biafo glacier. A map of the snout was published as Plate 31 in Rec. Geol. Surv. Ind., vol. lxviii, 1935. This year Spender carried out a more rigid survey with a Wild theodolite. During the four years that have elapsed the central portion of the snout of this glacier has retreated over a distance of about 51 o feet (156 metres). The nearest position of the ice to the south wall of the Braldu river was 950 feet (290 metres) in 1937. There seems to have been little, if any, seasonal retreat between May 1937, when we examined the glacier together, and August 1937, when I returned alone and made a few more observations. In 1892 Conway considered that the seasonal retreat of this glacier amounted to almost one quarter of a mile.

 

EXPLANATION OF PHOTOGRAPHS

1. View SW. from 18, ioo-foot camp, overlooking the K² glacier. Pale bands in dark rocks on either side of tributary glacier are wedges of limestone. 12th July 1937.
2. Granite peaks of the Biafo-Panmah watershed, that on the right being the 'Ogre', 23,900 feet. Nobande Sobande branch of the Panmah glacier in the centre. View SW. from Survey Station No. 10. 12th August 1937.
3. Syncline of Mesozoic rocks in the Aghil range. View SW. from the Aghil col (about 18,600 feet). K² in distance. Pyramid glacier flowing down to the Skam Lungpa valley in the right foreground. 27th June 1937.
4. Stratified series of the Aghil range, ranging in age from Permo-Carboniferous to Jurassic. Shaksgam river in foreground with the 'Confluenza island' of Desio. View NE. from Survey Station No. 2. 23rd July 1937.
5. Skamri peaks and Drenmang glacier, showing in the foreground metamorphosed Permo-Carboniferous rocks dipping to the south-east. View NNE. from Survey Station No. 14. 18th August 1937.
6. Contact of granite (pale) and slates (dark); Aghil range. View NW. from about 3 miles NNW. of the Aghil pass. 21st June 1937.
7. Ice-pinnacles on the Sarpo Laggo glacier, near camp 14,382 feet. 12th June 1937.
8. View of the snout of the Biafo glacier taken from about 12,900 feet on the Laskam spur. In 1909 the right (west) lobe of the snout extended up to the moraine ridge delimiting the lakes from the river gravels beyond. Considerable retreat of left (east) lobe since this glacier was visited in 1933. 27th May 1937.

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