PLEISTOCENE DEPOSITS OF LOP-NOR 



371 



(y + 4) -20 feet— Red clay. 



iy 4- 31 lu feet— Wblte clay. 



(y + 2) I.'i feet— ned clay. 



feet — White clay. 



used for irrigation, and most of the few sjd rings in the region are so saline 

 as to be absolutely nndrinkable in summer. Even in av inter, when it is 

 possible to cut out the best part of the ice around the springs and melt it 

 for drinking water, my men and I 

 found that after a drink we were 

 usually more thirsty than before, al- 

 though our thirst passed away within 

 an hour or two. It is noticeable that 

 the most highly saline parts of the 

 deposits at Lop are usually red. 

 Their appearance suggests that they 

 were deposited by the drying up of 

 successive sheets of water. The color 

 seems to indicate exposure to the air 

 before each layer was covered by its 

 successor. Probably the salt was de- 

 posited in great playas, which disap- 

 peared during dry seasons. At pres- 

 ent Lop-ISTor varies greatly in size 

 from year to year and is surrounded 

 by dirty brownish white deposits of 

 salt. 



^^^■^WXAm 



L-v-VM/^ 



(J + ■() le fepr— Yi-llowlsb clay. 



(1- + ■-■ I 

 (»+ 1) 



feel — Whllf .'lay. 

 feet— Ued flay 



VNCONFORMITIES AND BURIED 

 8TRAND8 OF LOP 



The unconformities in the Lop- 

 Nor deposits are ahnost as important 

 as the strata themselves (see plate 

 34). Those of figures 13 and 13 lie 

 at about the sauiC elevation on oppo- 

 site sides of the lake. As they are 80 

 miles apart, it is impossible to be sure 

 as to their relation. They appear, 

 however, to be of the same age. The 

 strata lying above tlie main uncon- 

 formity, A-B, in each case, seem to 

 correspond to those lying above the 

 break in figure 10. The unconform- 

 ity shown in figure 12 is the same as 

 distant. In figure 12 a great amount 

 of the presence of a large stream at th 

 formed. The gravels numbered 5 in 



(20) 18 feet— Sandy red riay. 



feet — SallDe red clay 



feet — Whitish green clay 

 ; feet — BaDded red aod white cla.v. 

 'i feet — Saline red clay; very {typslferoua. 



foot — White and yellow clay. 

 ' feet — Saline red clay. 



foot — White and yellow clayey sand. 



feet — Saline red clay, very gypsiferouB. 



foot — Sandy yellow clay. 



foot — whlliflh Kreen clay.,, . ,. 



fool— Red clayey sand. Uncontoralty. 

 feet — Slightly sHllno red clay- 

 foot — Yellow cloy. 



(12) 7 



(11) V4 



(lOJ 1 



O) 1 



(8) 6 



(7) 1 



(61 4 



(5) Vi 



(4) :l 



(3) y, 



(2) 4 



(1) 1 



feet — Saline red ciny. 

 foot — Yellow clay 

 feet — Saline red clay, 

 foot — Yellow sandy clay, 

 feet — Saline red clay, 

 feet — ^Whitish green clay. 



Figure 9. — Section near Localitij referred 

 to ill Figure 8. 



B and C are two sections supplement- 

 ary to A. They lie above it, but the 

 exact relationship is not known. Scale : 

 1 inch = 40 feet. 



that of figure 5, which is not far 

 of erosion has talvcn place because 

 e time when the unconformity was 

 the section were deposited by the 



