National Institute of Informatics - Digital Silk Road Project
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Southern Tibet : vol.7 |
THE VALLEYS OF NORTHERN TIBET.
555
At a time when great rivers flowed through the latitudinal valleys of Tibet, innumerable tributaries joined them from both sides. As the main rivers, the tributaries had also generally a latitudinal stretching. Even now after the enormous geomorphological and climatic changes which have taken place since the moist period we meet nearly every day on a meridional crossing of Tibet a new latitudinal valley. We have dealt with only the principal ones. Even if it would be easy to trace many secondary latitudinal valleys, such a task would serve no useful purpose. I will mention only one greater than the rest. It is situated between 331° and 34° North. Lat. and seems to have had its sources on the north side of BONVALOT's Mts. Dupleix and to have joined the river that passed by Aru-tso. Along its course we find from east to west the following lake depressions :
A lake 513 8 m. . . Littledale
Lac du sel rouge 4698 » . de Rhins
Near Gomo-tsaka 4843 » . Hedin
Near a lake 4901 » . Bower
Near a lake 5132 » . Bower
The mean altitude of these depressions is
4942 m.
It now only remains to say a few words regarding the folding troughs north of my valley of 1896. They are, of course, innumerable as all over Tibet, and it is sufficient for our purpose to consider only two of them.
Between the mighty system of the Arka-tagh with its more or less detached ramifications towards the north, and the Kalta-alakan, Piazlik-tagh and the western part of Astin-tagh, there is a folding trough beginning in the east with the Chulak-akkan valley of CAREY and DALGLEISH and continuing westwards across:
Bulak-bashi 3922 m
Bash-kum-köl 3882 »
Ayagh-kum-köl 3867 »
Aikin-otak 4795 m•
A Pass 5 I 08 »
Mandarlik in Patkaklik-darya 3 5 I I »
It would be of no use to calculate an average altitude for the whole stretching of this trough, for in the east it goes on without interruption into the Tsaidam Basin, and in the west by Cherchen-darya into the Tarim Basin. The most characteristic part of the trough is that of the two lakes, the mean altitude of which is 3875 m. Nor do the eastern and western flanks of this trough belong to the self-contained regions of Tibet.
The last, and more conspicuous folding-trough, lies altogether outside of the self-contained region. It has Akato-tagh to the north, and Piazlik-tagh, Kalta-alakan and Chimen-tagh to the south. Its valley is called simply Kakir, and its watercourse is directed to the lake Ghaz-nor or Chimen-köl at an altitude of 2837 m. The altitudes of these two troughs therefore indicate two steps downwards to the plains of Gobi.
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