国立情報学研究所 - ディジタル・シルクロード・プロジェクト
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Explorations in Turkestan 1903 : vol.1 | |
トルキスタンの調査 1903年 : vol.1 |
Dungsugotにある砂利で覆われた湖成堆積物 前の図と同じ特徴を示している 解説は図146を参照The gravel-covered lacustrine deposits at Dungsugot, illustrations the same features as the preceding diagrams. For explanation see fig. 146. |
RECONNAISSANCE IN CENTRAL TURKESTAN. 213
climate. The load of the streams was correspondingly decreased, and they cut downward until the relief was like that which is represented by the outer valley cut in the silt (B, fig. 147). At the saine time the front of the old silts was being gnawed back and the slope was being prepared on which the terraces (fig. 146) were later cut. The surface of the old lake deposit must originally have presented an unbroken slope (I H in fig. 146). The bed of the stream, the lower dotted line, I B H, must have presented an equally smooth although more concave slope. The two must have met at the lake shore when the water was at its lowest level. Even the most cursory inspection of the valleys and spurs shows that this point of meeting must have been far out in the swamp close to the present shoreline. Therefore the lake must have been small and shallow, and the climate must have been similar to that of to-day or possibly even drier.
Fig. I 48. The gravel-covered lacustrine deposits at Dungsugot, illustrating the same features as the
preceding diagrams. For explanation see fig. 146.
The next changes were those recorded in the terraces and in the gravel which fills the valleys represented in fig. 147. It is easy to infer that the lake must have risen and fallen twice, and that each rise was associated with the formation of a terrace and with the partial filling of the valleys with gravel, but of this we have as yet no direct evidence. The next rise of the lake of which we have positive proof was probably also the last. It deposited the recent silts (G, figs. 146 and 148), which rise to a height of too feet and bury not only the foot of the terraces, but also the isolated hills on which well up the springs of sweet water in the midst of the salt swamp. Now a last change of climate has again reduced the lake to very
small proportions.
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