RECONNAISSANCE IN CENTRAL TURKESTAN. 
l6l 
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 
earh- 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 
unconfonnable conglomerates are so coarse that they could only have been fonned 
Fig. 1 2 1 . — Sketch map, showing location of Figure 1 20. 
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 Tertiar\' 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 
thev were bent down where they are covered, and that the younger strata were largely 
fonned in the very basins which they now occup)-. 
