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Explorations in Turkestan 1903 : vol.1 |
Sketch map, showing location of Figure 120. |
RECONNAISSANCE IN CENTRAL TURKESTAN.
some basaltic lavas, as may be seen, for instance, in the Sugun Valley west of Shor Kul. The folding of the Paleozoic strata (see fig. 122) is of the sort which is associated with mountain building, hence at the end of the Paleozoic era or in the early part of the Mesozoic this part of Central Asia must have been highly mountainous. In evidence of this it may be pointed out that the succeeding unconformable conglomerates are so coarse that they could only have been formed
Fig. 121.—Sketch map, showing location of Figuie 120.
subaerially in a region of considerable relief, and yet at the time of their deposition the old folds of limestone and slate had already suffered great denudation. As a rule, the hard Paleozoic strata are found in the highlands, while the softer Mesozoic and Tertiary strata occur in basins among the highlands and mountains ; but this seems due less to the superior resistance of the older rocks than to the fact that they were bent down where they are covered, and that the younger strata were largely formed in the very basins which they now occupy.
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