THE SCIENTIFIC WORK OF THE GERMAN HIMALAYAN EXPEDITION TO NANGA PARBAT, 1934

Professor R. FINSTERWALDER, Dr. WALTER RAECHL, and Dr. PETER MISCH

1. GENERAL
2. GEODETIC AND TOPOGRAPHICAL SURVEYING
3. GEOGRAPHICAL STUDIES¹
4. GEOLOGICAL STUDIES

 

 

There are few places in the world where the earth's crust is open to a greater depth and where it lies more freely exposed than in the Himalaya, and more particularly in the region of Nanga Parbat, the north-western pillar of these mountains. Here the Indus flows at a height of between 3,000 and 4,000 feet in a hot arid valley, 21,000 feet lower than the snow-covered crests and ridges of Nanga Parbat. Between the valley bottom and the mountain crests there are a number of climatic and morphological zones, with considerable differences of detail: The climbing expedition provided the opportunity for some scientific research on these regional questions as a contribution to the great problems of the North-Western Himalaya as a whole. Previous research work done in the Himalaya has been extensive rather than intensive; we had the opportunity for intensive rather than extensive work. Both are essential to the solution of the great problems of geography and geology that have to be solved. It is hoped, therefore, that our observations will add to the structure of Himalayan research; not till our final results are compiled can this hope be fulfilled. In the following summary we can only indicate the nature of our work and observations.

The scientific group of the expedition consisted of myself, Dr. Walter Raechl, and Dr. Peter Misch. Our work comprised (1) Geodesy, Cartography, and Glaciology, (2) Geography, and more particularly Geomorphology, and (3) Geology and Petrology. The programme and scope of this work was arranged so that the members could travel together in one group, the work of each being complementary to that of the others. Our observations covered the whole of the Nanga Parbat massif and its immediate neighbourhood; in all branches of our subject there were interesting and important problems to be solved.

The region of Nanga Parbat is not unknown. The Survey of India has carried out general geodetic and cartographic work. Dr. D. N. Wadia has made a geological survey. We were not therefore concerned to explore scientifically as large an area as possible, but to apply modern methods to a limited region. For geodetic surveying and glaciology we intended to use modern stereo-photogrammetry; in the sphere of geomorphology we must apply the methods used in the Alps for questions relating to the Ice Age; the geologist had to consider the new gefugekundlichen methods. Intensive examination of the whole region necessitated high climbs on the steep slopes of Nanga Parbat, and the task was not easy even for fit climbers. Although we often worked separated from the main group of climbers, we owe much to their help, and it is with deep gratitude that we remember our friends who have remained on the mountain. To the initiative and talents for organization of Merkl we owe our opportunity. To him was due the possibility of alpinists and scientists working together on this expedition, and without him the scientific work would have been impossible.

 

 

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Our plans included the compilation of an accurate contoured map of the whole district, by terrestrial stereo-photogrammetry. Such a map was to be the basis of our research in geological and geographical questions not only now but in the future. This is meant in no sense as a criticism of the existing map recently published by the Survey of India. The cartographic work of that department surprised us by its high quality and was most valuable to us. But for the detailed studies we were engaged upon, the scale (1 inch to 4 miles, 1 : 253,440) was not large enough, and the method, plane- tabling, was not accurate enough. Even the very best planetabling is much inferior to photogrammetry, particularly in so difficult a mountain region. Nevertheless, British officers have carried out some photogrammetric survey which was of both theoretical and practical value to us. During certain flights along the Indus valley oblique photographs had been taken of Nanga Parbat, particularly of the upper Rakiot valley. Captain D. R. Crone, r.e., has since given a brief account of his method of compiling a map from these obliques, on a scale of 1:100,000; where it has been used successfully in mapping the north-west face of Nanga Parbat,¹ and it will be of more than technical interest to compare his results with our contoured map to be drawn by ground stereo-photogrammetry.

Nor was it the first time that ground stereo-photogrammetry had been employed in the highest Himalaya. The pioneer of the method was Major, now Professor, Kenneth Mason, who used the Wild photo-theodolite in the Shaksgam in 1926, and plotted his map with the Wild Autograph in Switzerland.¹ In 1931 Karl Wien surveyed by the same method the Zemu glacier in the Sikkim Himalaya, and from his photographs I compiled a map on the scale of 1 t 33,333-² But now we proposed to survey not only a single glacier, but a whole group of the high Himalaya, about 1,000 square miles in extent. I had myself already made a similar survey on the Pamirs,³ but I now intended to test the method in the wilder and more difficult Himalaya. I had the assistance of Dr. Walter Raechl, who had worked with me in the Alps.

 

The photogrammetric method employed was almost the same as that used on the Zemu glacier. Now, however, we used a larger instrument, the light Zeiss field photo-theodolite, with a 13 X 18 cm. image and a vertical image-plane. We used 115 photogrammetric base-lines and took 350 survey photographs, mostly at heights between 13,000 and 16,000 feet, just below the limit of snow. The photographs include the whole region without any important gaps, and from these we shall be able to make a complete and accurately contoured map on the scale of 1 : 50,000, plotted automatically. In order to fix the photogrammetric stations, we triangulated the whole district. The accuracy required was to about 3 feet both for position and height.

In conjunction with the triangulation we measured the plumb- line deflexions by determining astronomical latitudes from star observations at fifteen stations whose geodetic latitudes were obtained from the triangulation. The difference of the astronomical and geodetic determinations of latitude is, of course, a measure of the deflexion. The accuracy is expected to be about one second of arc and though the results are not yet available, the observations at so many as fifteen stations should give a very good idea of the form o the geoid in the region of Nanga Parbat.

Glaciological observations were also carried out. On suitabl* profiles of the glacier-tongues we measured the velocity of ice-movement by a series of stereo-photographs, as I had already done 01 the Pamirs. By knowing the velocity of ice-movement in a profile the depth of the glacier-ice and the volume of ice flowing through the profile can be determined by Lagally's formula. We surveyed four profiles on the chief glacier of the group in the Rakiot valley and also on two glaciers in the Rupal valley to the south of Nanga Parbat.

 

 

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My activities as geographer on the Nanga Parbat expedition embraced researches in geomorphology, plant-geography, and human settlement, besides participation in the photogrammetric survey. It was possible to combine these activities to some extent. In addition, daily Weather observations were carefully made, a task that was carried out also in the climbing group by Ulrich Wieland. In the main Astor and Indus valleys we visited and examined heights between 10,000 and 16,000 feet; in the upper Rupal glacier region Misch, the geologist, and I worked up to 18,300 feet; and on Nanga Parbat we reached 21,000 feet.

My chief task was to carry out in this limited region of the Himalaya an accurate geomorphological examination on lines similar to those employed in the Alps now for a number of years. With a practical knowledge of alpine development and form I could, during my field work, draw comparisons between the two mountain systems, which were most valuable in forming an opinion of the geomorphology of this Himalayan region.

The Nanga Parbat massif is bounded on the east, south, and west by deep, narrow gorges (the Astor, Rupal, and Bunar valleys). Only on the north and north-west does it slope down towards the broad longitudinal valley of the Indus. Just as in the Alps, so here one observes a 'storied' or step-like type of construction, as expressed by platforms, levelled ridges or 'benches', ridges of equal altitude and steps in the valley bottoms. The phenomenon is more noticeable in the mountain hollows than in lower parts of the valleys. In the upper Rakiot and upper Rupal nullahs, for instance, about seven steps of different level can be recognized, those at about 13,000 feet, 15,000 feet, and 16,500 feet being the most marked. They can be traced in the hills bounding the Astor and Indus valleys.

Specially noticeable in the landscape are the gentler land-forms between 13,000 and 13,700 feet, where the rounded and flattened ridges and broad rudimentary valleys, cut short in front, resemble the old morphology of the Deosai plateau, about 40 miles to the south-east. The change in cross-section between the upper and lower parts of the same valleys is surprisingly marked: U-shaped valleys change suddenly to narrow V-shaped gorges: pre-glacial structure and composition have been influenced by glaciation in the upper parts; post-glacial fluviatile erosion and young elevation have co-operated in the lower.

 

It is possible to estimate from the remains of moraine, and partly also from the slightly formed troughs in the uppermost parts of the valleys to what extent there has been glaciation. From the fact that below 7,000 feet there are no signs of glaciation, one can conclude that the Nanga Parbat glaciers were never so extensive during the Ice Age as those of the Alps, where the tongues of huge valley glaciers covered even the foreland. But the corries at a height of 14,000 feet and over (the existence of which was doubtful in the Himalaya) are irrefutable evidence of extensive glaciation on the slopes at some period.

Post-glacial and recent movements of the valley glaciers are shown by four systems of moraines which are generally recognizable at the Rakiot, Buldar, Lotang, Sachen, Chungphar, and Bazhin glaciers; they are mostly covered by high or young woods. Between the periods of the most ancient advances of the glacier snouts, climatic changes must have caused considerable degeneration of the ice and 'retreat' of the snout. The great filling up of the valleys is largely connected with these periods of degeneracy. For long distances, terraces of loose rock are preserved, showing on the sides of their steep slopes a marked formation of earth-pillars. To-day the glacier streams have cut deep down between the old lateral moraines, and the remnants of even recent terminal moraines lie already a considerable distance from the glacier snouts. The whole picture is one that suggests general recession of the glaciers for some time, with short and occasional interruptions.

The character of these valley glaciers varies with the morphology. Below the steep east wall of Chongra peak (Lotang and Sachen glaciers) as well as below the south wall of Nanga Parbat there exists the type of glacier that has no neve basin, while the high-level erosion surfaces in the basins of the Rupal and Rakiot glaciers have permitted the formation of neve regions. With the first of these types the valley glaciers are fed only by falling ice and snow avalanches; with the second, they originate from the neve reservoirs, but also increase their volume farther down their course from the ice-covered slopes that enclose them.

In contrast to these mountain valleys the deep Indus valley, with its broad, high-lying floor at 4,000 feet, differs strangely. It forms a desert embedded between the icy glaciers of Nanga Parbat and the range beyond. The interglacial or post-glacial gravel filling appears here in three, four, or five systems of terraces, which are particularly well preserved at Bunji and Bunar, while they are discontinued in the narrows at Leychar. The gravels are underlaid by sands (Mehlsande) south of Bunji, which thin out gradually as one ascends the valley; in the other direction they end at the rocky narrowing of the valley floor at Leychar. They appear to be the sediments of a former valley lake which disappeared when the waters cut through the rock dam. No signs of a former glacial period of the Indus valley could be found between Bunji and Bunar.

 

 

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Our task was to obtain as accurate and detailed information as possible regarding the Nanga Parbat group, which belongs to the Himalaya, the highest and wildest of the young folded chains of mountains. For the geologist this implied examination of a portion of the Himalayan crystalline complex. For the Nanga Parbat group lies in the inner zone of the mountains, which consists chiefly of crystalline rocks. Minute examination of this limited section of the Himalaya should be bound up with the general geological study of the Himalaya as a whole, the responsibility for which is undertaken by the Geological Survey of India. My work tries, therefore, to make a contribution to the solution of a number of questions connected with the crystalline rocks of the Himalaya. Among other problems of interest to the geologist are the age of this crystalline group and its tectonic connexion with the folded system of the Himalaya. The geologist had therefore to make as accurate a geological survey as possible of the Nanga Parbat region, and to examine the peculiarity, connexion, and mutual affinity of the different rocks, and the tectonics and folding, both generally and in detail.

As with the topography, the Nanga Parbat region was geologically no undiscovered land. Mr. D. N. Wadia, of the Geological Survey of India, who has done so much valuable research in the northwestern Himalaya, had also travelled in this district. His report was very valuable for my special geological-petrographical research.¹

The geologist, like the topographer and geographer, could not limit his investigation to the main route of the expedition, but had to travel over the whole region. At all important places geological sections were made, from the valleys to the higher regions. It was most important also to climb high in order to recognize connexions which could not be seen from below; and the geologist on Nanga Parbat must be a climber as well as a scientist.

 

The co-operation of the triangulator was most valuable for my work, for I was able to use the points he fixed in the field, and to make geological drawings from the photogrammetrical base-lines. It will therefore be possible to show the geological data very accurately on the map.

I collected a rich and complete series of rocks from the whole region. These will be examined microscopically and should serve to complete and confirm the results already gained from the field- work. Many questions cannot be definitely solved until such microscopical work is completed, and at present I can only draw a general picture and suggest the direction in which the final results will lead.

The Nanga Parbat group is a massif composed of an envelope of sedimentary gneisses, very rich in petrographical types and injected by granitoid gneiss, more so in the inner part of the massif than at its edge. At the edge of the massif the sedimentary gneisses can be clearly recognized as such, and in most cases they are sharply limited against the injection layers. In the inner part of the massif, on the other hand, a bright coarse gneiss has originated, looking macroscopically entirely like a granitoid gneiss. But included in the gneisses there are to be found, again and again, layers of marble and other crystalline rocks, which are clearly of sedimentary origin. This is true also for the highest portions of the central group, for instance, the north and south walls of Nanga Parbat itself. Thus the massif, even in its central core, does not consist of pure granitoid gneiss— still less of unfoliated granite—but here is also composed of a mixture of sedimentary material and granitoid gneiss.

In the whole massif, the Nanga Parbat gneisses are strongly folded and compressed. Besides the major folding can be observed intensive minor folding. In no place is this folding younger than the crystallization of the gneiss. The dip of the gneisses is generally steep; the strike generally from south to north. Thus it is diverted strongly from the normal Himalayan direction of the region to the south-east. This is connected with the fact that we are here at the north-western end of the Himalaya, where it turns backwards at the northernmost point of the continental block of India and meets another mountain trend. This characteristic trait of the north-western Himalaya has been made well known to us in connexion with the outer sedimentary folds by the researches of Mr. D. N. Wadia.¹

 

On both sides the Nanga Parbat gneiss meets huge masses of basic intrusive rocks (that is, igneous rocks of basic chemical composition solidified at depth). With the exception of certain local zones these masses show in their interior no signs of tectonic deformation, but they still possess their original structure of solidification. On the other hand, in the general neighbourhood of the gneiss, they are strongly foliated and metamorphosed, and in its immediate vicinity they are intimately mixed and folded with it. Thus we can recognize that a common tectonic process has influenced the gneisses and the basic rocks, and in many cases there is macroscopic evidence of a crystallization process common to both, though a final decision can only be obtained by the microscope. These facts are important for determining the age of the Nanga Parbat gneissification, because the age of the basic rocks can be determined in the south-east of the group. In this region the relation of the basic intrusions to the volcanic trap of the Upper Carboniferous-Permian Panjal system leads to the assumption that the basic intrusions are nearly contemporaneous with, or somewhat younger than, the Panjal system. Mr. D. N. Wadia has already pointed this out.

After an intensive survey of the Nanga Parbat group, I made shorter excursions to the south-east while on my way back. I was anxious to explain the relation of the Nanga Parbat crystalline rocks to the non-metamorphosed sediments existing therfe. This was of great importance to the question of the age of this crystalline mass and of its position in the folded system of the Himalaya. The Nanga Parbat gneiss continues southwards to this region, and, at the same time, the basic rocks on its eastern side that bordered it before are now replaced by sediments. Here I could observe a slow change from the gneisses to less metamorphosed schists, which are followed by the Upper Carboniferous-Permian Panjal system at the same dip of foliation, and without a visible angular discordance. Thus no sharp cut is to be seen between the gneiss and the less altered sediments; neither is there any tectonic line—for instance, a nappe boundary— nor is the gneiss cut off unconformably by a younger sedimentary system overlaying it. Even higher up in the section (between the schists overlying the gneiss and the strata of the Panjal system), it is not possible to recognize a true angular discordance in the field. In this connexion it is interesting to state that conglomerates inlaid in the Panjal strata contain no single piece of gneiss.

The conditions as described suggest the idea that the origin of the Nanga Parbat gneisses out of sediments, and the injection of granitoid gneiss material combined therewith, might possibly not be older than the Panjal system (and the basic intrusions), and consequently not older than the folding that has affected the Panjal system. The Panjal system was not folded before the time of the great Tertiary Himalayan folding. Thus the same period would account for the age of the Nanga Parbat gneissification. In this case we would not have an old crystalline block, but a zone of young metamorphism. In accordance with this would be the fact that the Nanga Parbat crystalline rocks and the sedimentary folds that follow in the southeast fit into a uniform architecture with the same direction of strike. These conclusions cannot yet be definite, for proof in this meta- morphic region can only be given with the help of the microscope. In the microscopic examination it will be necessary to analyse accurately the boundary zones of the gneiss against the basic rocks, and also the sections leading from the gneiss up to the Panjal strata. This means that we must analyse the tectonic movements and the crystallizations (thereby also the different combinations of minerals, &c.) that are to be seen in the different rocks. We have only mentioned the most important of the many observations made in this boundary zone of the gneiss.

I should also mention that in the whole region of the expedition there are no traces of nappe structures, and the construction of the folds appears to be comparatively simple.

Younger than all the rocks here described are the granitic intrusions which break through these rocks and are nowhere gneissified themselves. Several types of granitic rocks can be distinguished. I could also observe in a particular region on the northern edge of the Nanga Parbat massif a folding which is much younger even than the chief Himalayan folding. At this place sandstones of the youngest Tertiary or of the oldest Quaternary period are folded into a steep syncline along the Indus valley. Thus this very young folding appears here locally in the crystalline inner zone of the Himalaya.

 

POSTSCRIPT.

The stereo-photogrammetric map accompanying this paper is only preliminary and not yet complete. A considerably larger area has been surveyed photogrammetrically and the gaps seen on this portion have now been plotted. A more complete map is published in Forschung am Nanga Parbat.

I should like to express here my deep gratitude to the Deutscher und Oesterreichischer Alpenverein for the great assistance they have rendered in making possible the development of this map.

R. F.

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