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it is met by a stream coming from the west, joining the waters coming from the east. This irregularity—the direction of drainage-proves that the origin of this valley must be a peculiar one, and so it is. The Gôkteik-Kunlôn valley marks a line of great disturbance of the strata ; two large faults, or probably two systems of compound faults, running from the south-west to the north-east, are distinctly discernible. Along these faults the country was thrown down, but as this action did not of course take place very regularly, one part moving perhaps stronger than another, the peculiarity of the drainage system is readily explained. It is very common in this valley to meet isolated hills rising abruptly in its centre; they are nothing more than small parts of the sinking blocks which have become jammed. Sometimes they still touch both sides of the valley, forming a kind of bar or ridge. Such bars, breaking seemingly the continuity of the valley, are numerous and of smaller or larger extension, and they account also in some degree for the direction of the drainage. A most perfect instance of such a bar may be seen between the villages of Manpeng and Meungyaw. Here the bar has a length of about 5 miles ; the breadth may be about the same. The bar consists of red sandstone, resting on blue limestone, while the hills on both sides are formed of blue limestone. Thus the lateral boundary between red sandstone and blue limestone is as distinct as possible, proving plainly the existence of a fault on either side of the bar. Similar bars may be seen east and west of Lashio, but I have never noticed them so clearly discernible as in the instance quoted above.
The direction of the faults is distinctly marked, on the map of Upper Burma (scale i inch=4 miles, sheet No. 4, south-west), by a series of precipices running parallel on either side of the Gôkteik-Kunlôn valley in a direction from south-west 10 north-east. On the map these precipices are shown as short hill ranges. This is, however, not quite correct, as these "ranges ” have only one slope, or, better, precipice, facing the valley. I stated above that I believed there is a system of compound faults. The reasons which make me think so are that there are several of these precipices following each other in the directions towards the centre of the valley. The rise towards the plateau therefore goes in steps, and it is evidently a system of step faults that produced this feature of the country, the precipices representing the fault scarp on both sides of the valley. Of course this does not take place all along its length, but it can be well seen on the northern side between Bawgyo and Thibaw.
Valleys similar to the Gôkteik-Kunlôn valley will be met within the Shan plateau, although they are not of as great importance as it is; such valleys are the Namma valley, a part of the Myitngè valley, and others.
(c) Two systems of valleys.—There are therefore two systems of valleys, the first one running from north 10 south, the second one running from south-west to north-east. While the direction of drainage is always to the south in the firstnamed system it does not always keep to one direction on the second system. It is rather difficult to say which of the two systems is the older one, but considering that the second system contains strata which, so far as I know, are not found in the valley of the first system, and that whenever a valley of the first system crosses one of the second system, the first one is thrown off its direction, I consider the eastwestern system to be the older one. There are, however, further proofs required and I give this theory with every reservation.
Section II.-GEOLOGICAL OUTLINES OF THE COUNTRY BETWEEN THE
IRRAWADDI AND THE SALWEEN. The strata taking part in the composition of this country belong to the following formations :
1. Gneissic formation.
7. Volcanic rocks : Porphyry of unknown age, granite of gneissic age. The limestones of the palæozoic prevail, and then follow the shales of the submetamorphic formation. Of inferior importance is the gneiss; while the red sandstones and the strata of tertiary formation, such as sandstones, clays, and coal-seams, are only locally developed. The alluvial deposits may be found anywhere where there is room left, the hill clays taking the prominent part. Of the volcanic rocks, the granite is only found in the north ; the highly interesting porphyry is only known up to now by pebbles from the Namma stream.
1. The Geissic formation.—The gneissic formation is particularly developed in the northernmost part of this territory in the Mainglon State and along the frontier of the Ruby Mines district. Its mineralogical composition shows evidently the character of the Himalayan gneiss, being of white or greyish colour, the common felspars being orthoclase and albite. The same gneiss is again met with at the outskirts of the Shan plateau near Kyauksè, where it forms thick beds. Here it is associated with mica schists. Gneiss is also found along the right bank of the Irrawaddi in a small band extending from Sagaing to the north. In the Mainglôn State, as well as near Kyauksè, the gneiss seems to be associated with eruptive granite. It is, however, not quite certain whether the granite is true eruptive granite, although from the way in which it occurs this seems very probable.
2. The Submetamorphic formation.-The submetamorphic formation is, as far as I know, only Jeveloped in the northern part of country here to be dealt with. It seems, however, that its southern boundary is not far from the northern fault limiting the Gôkteik-Kunlôn valley. The peculiar topographical features of the country north of the line just mentioned seem therefore to be chiefly due to the nature of the gneiss and shales which are developed here. The strata belonging to the submetamorphic formation consist of blue or greenish shales containing frequently veins of white quartzite (? fault-rock), of somewhat honeycombed appearance. The bulk of the quartzite pebbles met with in the gravels of the plains seems to me to originate in the destruction of these quartzite veins.
3. The Paleozoic formation.—T'he palæozoic formation is of very large extension in the country east of Mandalay. Most probably the isolated hills rising from the plains belong to it, although they are very much metamorphosed. It certainly begins at the foot of the hills and extends from there to the east as far as the Salween, and since the Trans-Salween hills have the same appearance as those to the west of it, we may fairly conclude that it extends further still beyond the Salween. Its northern limit is roughly marked by the northern slope of the Gökte ik-Kunlôn valley, although both sides are formed by it. How far it extends to the south is not known at present. If, however, the limestone hills east of Moulmein are of the same age as those near Mandalay, the palæozoic formation has a considerable extension into Indo-China.
The strata consist of limestones only, and dark blue colours are prevalent; scarcer are greyish, green, and red limestones. According to their positicn I am able to distinguish two groups for the present, namely,–
(a) The lower group: Mandalay limestone without fossils.
age. (a) The Lower group, or Mandalay limestone.— The Mandalay limestone forms the foot of the Shan hills; and very likely some of the isolated hills rising from the plains belong to it. It is of a dark blue colour, bedded in thickish layers and seemingly without fossils. Along the outskirts and in the plains, the Mandalay limestone is very much metamorphosed. In the plains it is changed into a white crystalline limestone which is traversed by numerous runs of fault-rock and an eruptive rock, the nature of which can only be determined by microscopical examination. Along the western slope of the Shan plateau the Mandalay limestone has also suffered another kind of metamorphosis by pressure. This pressure has perfectly crushed the rock to small fragments, which became again cemented by the deposit of white crystalline limestone. The limestone is thus traversed by numerous fine white veins which produce a very good effect on the black background, and I should therefore think it would do very well for ornamental purposes. A distinct zone of about 2 miles in breadth of such breccia limestone can be noticed along the western slope of the Shan plateau.
(6) The Upper group, or Pyintha limestone.—The Pyintha limestone is only well seen between the 22nd and 26th miles on the road from Mandalay to Maymyo. It consists of grey, greenish grey, reddish grey, and red limestones, frequently rather clayey. It is bedded in thinner layers than the Mandalay limestone, and breaks into fine big flags. I was fortunate enough to discover a small fauna in this limestone, about which I have already published a short notice in the Records of the Geological Survey of India for 1890, (Vol. XXIII, p. 78). The following fossils were collected :Crinaidarum, gen., isolated links and fragments of the stem ; belong evi
dently to two different species. Echinosphærites kingi, spec. nov., a gigantic species of this well-known
genus of the lower silurian group. Orthoceras sp. cf. regulare, in numerous fragments. Although the specimens were very much disfigured by pressure, they were quite sufficient to determine the age of this limestone, proving it to belong to the silurian formation, more particularly to the lower silurian one. As the echinosphæ. rites limestone of Northern Europe ranges close to the basis of the lower silurian group, we may fairly surmise the same age to be that of the Pyintha limestone. Now, as the Pyintha limestone certainly rests on the Mandalay limestone, the latter must necessarily be of an earlier age, and, being of a considerable thickness, it may be supposed that it represents the equivalent of the cambrian formation. Unfortu
nately I was not able to examine the strata which followed the Pyintha limestone, the ground being not very favourable for a considerable distance, when there were again some cuttings along the road. A blue limestone of similar nature to the Mandalay limestone was noticed, and the same limestone was found as far as the Salween. Though I searched carefully, I did not discover a single fossil. Now, it is difficult to say whether this blue limestone is of the same age as the Mandalay limestone, or whether it represents a younger group. Only detailed examination extending over a large area and for a long time will settle this question,
4. Red sandstone of undetermined age. As far as I know at present, the red sandstone is only found in the Gôkteik-Kunlôn valley, namely, east of Thibaw and in the neighbourhood of Lashio. It rests on the blue limestone, but whether conformably or not I could not ascertain. No fossils have been discovered in this series of strata, and it can therefore only be said that they are of post-silurian age.
5. Tertiary formation. It is certainly very remarkable that from the long series of strata which lie between the silurian and the tertiary epoch, no other traces could be found but sandstones the age of which is very doubtful. If they should prove to be of palæozoic age, the whole of the mesozoic group up to the most recent tertiary beds would not be represented in this part of the Shan hills, and we are therefore led to believe that either the once existing mesozoic strata have all been washed away, or that the present Northern Shan hills form part of an old continent which was laid dry at a very early epoch. The present Shan plateau forms now only the remnant, so to say, of a once mountainous country, the mountains, however, having all disappeared, shaved off apparently by marine denudation, and it is most likely that the Shan plateau formed up to tertiary times a continent. Further examination, particularly to the south, will prove whether there is any substantiality in this theory.
The tertiary strata are, as far as at present known, only found in the valleys belonging to the second system, i.e. those valleys which run from south-west to northeast. As these valleys, however, originated by the downthrow of a part of the strata along a system of parallel faults, it is clear that the tertiary strata must once have been at a higher level than they now are; provided that it cannot be proved that they have been formed locally, namely, at the very same place where they are found now. If the first theory is found to be correct, the tertiary strata must formerly have had a larger extension. They were, however, nearly totally destroyed, and only those parts were saved which were thrown down from their original level. Should they, however, have been deposited locally, it cannot be expected that they will have a large extension. Although this question seems to be of only scientific value, it has a most important practical side when we come to estimate the extension of these coal-fields. As regards the Lashio coal-fields, the facts are not strong enough to disprove absolutely the theory that they are only local deposits, but as regards the Namma-Manzè coal-fields, the observations are strongly in favour of the downthrown block theory; that is to say, that the present coal-fields form only part of beds, once more extended, which have been preserved by sliding down in a kind of trough in which they now form the core. It is, therefore, also possible that the Lashio coal-field is of the same origin. This theory being admitted, it will give valuable hints where to look for further coal-fields; it is in the valleys of the second system that they may be expected, neither on the heights of the plateau nor in the valleys of the first system. Subsequent examinations will be necessary to
produce further proof, but whatever is known at present about the different coalfields in the Northern Shan States seems to support this theory.
As regards the age of the beds, they are apparently of late tertiary age. The strata in the Lashio valley are different to those I have seen in the Chindwin. The strata in the Namma valley, however, resemble those found in the Chindwin. The fossils which have been found, the numerous fragments of a small Planorbis-like snail and another big gastropod, are too insignificant; they are, besides, so much disfigured by pressure, that it will be impossible to identify them. The question of the age of the Shan coal-fields must for the present remain open, until further more significant fossils can be found. For the present it can only be said that they are probably of late tertiary age.
The strata consist of sandstones, clay, and coal seams. The sandstones are finely grained, of white or yellowish colour, rather soft. They should, however, form a good roof; the clays are grey or brown, easily softened by water.
The coal occurs in beds of various thickness, from 2 inches up to 30 feet; thin seams are not frequent. The average thickness of the seams in the Namma coal. field is 5 to 6 feet; in the Lashio coal-field even higher still. It is very difficult to give an estimate of the total number of seams for the reasons which I explained in the preface ; for instance, it is not quite settled yet whether in the Lashio fields there is only one or two big seams, or whether there are several seams. In the Namma coalfield the probable number may be 10 to 12 seams. At least I was able to distinguish that number of different seams. It is, however, not unlikely that there are more still.
The aggregate thickness of coal in the Lashio field is certainly more than 30 feet, in the Namma field about 50 feet. Nothing is known for the present about the other fields.
As regards the physical structure and chemical qualities of the coal, I shall discuss them according to 12 assays, of which 11 were made by the Chemical Examiner in Rangoon, and one in the Laboratory of the Geological Survey at Calcutta. The following table will give the results of this analysis :