IIIF Color HighRes
National Institute of Informatics - Digital Silk Road Project
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| IIIF Color HighRes |
| Southern Tibet : vol.7 |
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Citation Information
294
DREW ANI) OTHERS.
In 1869 Drew went across the plateaux to the eastern branch of the Kara-kash partly following JOHNSON'S, partly CAYLEY'S footsteps. He gives a good description of the »Southern Watershed», which is situated north of Chang-chenmo. Here he crossed a pass 19,500 feet high. He is right in saying that the passes in this tract are not much below the general level of the ridge. The rock he found to be shale, with interstratifications of sandstone. From its northern side the small streams go to the salt lake farther east. Still farther north is Lingzi-tang, separated by the Lokzhung Mountains from the northern plains, which he calls the Kwen-lun Plains. The average height of Lingzi-tang he calculates at 17,200 feet, very well in accordance with HENDERSON'S 17,300. West of Lingzi-tang there are »bolder hills and even snowy peaks ; in these there is a gap, to follow which would lead one down to the River Shayok». But he does not say that this is in reality the Kara-korum Mountains.
He found that the Lingzi-tang forms an isolated drainage basin. The whole ground has been deposited in a lake, a fact which had already been proved by JOHNSON. Drew found no means of ascertaining the depth of the deposits, and could follow them to 20 feet only, in the deep parts of the basin. At the margin, along the foot of the Lokzhung Range, he saw how the light-coloured flat of hard clay ends with a marked boundary against ground sloping about 2° upwards.
North-west of Tsothang he found complete beaches, — parallel curved shingle-banks, partly cemented by carbonate of lime dissolved from the stones themselves, which are of limestone. Such beaches were seen up to 150 feet above the flat plain. There has thus been a lake, the shore of which went along the edge of the Lokzhung Mountains, and there are evidences of a still higher water-level. Some margin-marks were also seen along the southern edge of the basin.
In the Lokzhung Range which is crossed by the path from Tsotang to Thaldat, different ridges are of different rock. There is an older encrinitic limestone, ferruginous sandstone, and above that a limestone containing Hippurites, unconformably on the older limestone; other portions of a light-coloured limestone or crystalline marble, make conspicuous white rocks.
His Kwen-lun Plains are situated between the Lokzhung and Kwen-lun Mountains i 6,000 feet high. The upper plateau is in parts covered with fragments of a brown calcareous cake an inch or less in thickness.
He discerns between HAYWARD'S Kara-kash the real source, and the eastern Kara-kash. The latter river is bounded immediately on the north by the main Kwenlun chain, on the south by a nearly parallel line of mountains of slate and shale; otherwise he makes the Kwen-lun chiefly granitic.
North of Thaldat he also found shingle -beaches up to 8o or 100 feet above the plain. And after a very careful and interesting analysis of the materials and
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