I02 
EXPLORATIONS IN TURKESTAN. 
granitic fragments, with many large blocks, lo or 15 feet through. Some other 
large slides were crossed fartlier south. These came from the west end of the 
Chaar Ta.sh and ran \vestward into the valley of the Oi-kain, a branch of the 
(eastern) Kugart-su. One of the slides blocked the valley and caused the formation 
CHAAR-TASM RANOC 
Fig. 69. — Ten-mile section of a Landslide in the (eastern) Kugart Valley, looking north- 
east. The present river valley is eroded in horizontal gravels that occupy an older 
and much wider valley eroded in tilted conglomerates. 
of a large meadow, now .somewhat terraced, ne.xt upstream. A little farther south 
the Oi-kain has been superposed on the resistant rocks (apparenth- limestones) at 
the southwest end of the range, and has there cut an impassable gorge ; hence the 
trail climbs over the ridge on the southwest and then descends into the open upper 
valley of the same stream. 
THE TERRACES OF THE NARIN BASIN. 
The terraces of the Alabuga River in its valley through the Narin formation 
were among the most interesting that we saw. It has already been stated that the 
Narin conglomerates and clajs had been much eroded after their deformation. The 
terraces now to be described occur in the valley that has been eroded below the 
broadly degraded surface — a true plain or a peneplain over large areas — of the Narin 
strata. The terraces were first seen in the valley of the Makmal, where three or 
four steps occurred. The uppennost Makmal plain was broadly sheeted over with 
gravels, even where it tnnicated the tilted clays. The spurs of the higher terraces, 
Fig. 70. — Tv^o-mile section of Terraces in Alabuga Valley, looking east. 
as well as the residual hills that surmoinit the highest plain, assume a more and 
more minute pattern of dissection or bad-land fonn, as the clayey strata toward the 
center of the basin are reached. After passing southward through the Ulu-tuz 
gorge in the salt-bearing anticline, we came out upon a well-defined terrace plain 
of the Alabuga \'alley and crossed it to the trench of this river, which was incised 
150 or 200 feet below the plain, as in fig. 70. Here several terraces were seen on 
the north side of the trench, while a single bluff rose on the .south side. The bluff 
showed a heavy deposit of gravel, capped with 20 or 30 feet of fine gray loess-like 
silt at the level of the terrace plain. Many springs issue from the blufll" at the 
