LOESS NEAR JIZAK. 
59 
would be relatively barren and the finer material would be blown from it with 
relative ease. It is here assumed that the loess is not chiefly supplied from the 
products of weathering on uplands and mountains, where the finer soil has less 
lime than loess contains, but that it comes in greater part from flood plains, where 
the finer silt, largely produced by the mechanical attrition of cobbles and gravels, 
may be highly' calcareous, as has been pointed out by Penck. 
LOESS NEAR JIZAK. 
A loess deposit of unusual interest was seen on June 17 on the uplands 
north of the Zerafshan, where the railroad contours around the eastern spurs 
of a detached part of the Turkestan range, west of the valley of the Sankar. The 
Sankar follows a valley that is rather sharply cut down in an upland or local pene- 
plain. The upland and the loess upon it are briefly described by IMushketof 
(1886, 355). The valley is about 100 feet deep where the railroad enters it, but the 
depth increases to 300 or 400 feet farther north, where it opens on the broad 
Fig. 34. — Diagram of Railroad Cut, south of Jizak. 
Hunger (Golodnaia) steppe near the town of Jizak. The valley floor is usually 
about a quarter of a mile wide ; it narrows where a belt of harder rocks forms 
"Timur's Gate." The valley sides are graded, except for the outcrops of the most 
resistant ledges. The upland or peneplain, where it is preser\-ed on the spurs 
between the numerous side valleys, truncates the disturbed rocks of the district 
ver>' evenly. The side vallejs that dissect it are fairly well open and graded far up 
the mountain slopes on the west. Kurgans (mounds) occur in some of these 
valleys. As the steppe is approached, the side valle)s increase in depth and width, 
and the even upland of the spurs is replaced b)- maturely rounded hills. Then the 
steppe suddenly opens, as if the upland were terminated by a fault or sharp bend; 
for if the level of the upland were prolonged northward it would run out into the 
air, far above the present plain. Its even profile was well seen by looking back 
from the train after we had run some miles out on the plain. The main and branch 
vallej-s of the Sankar must have been eroded after the faulting and uplift of the 
district with respect to the steppe. 
The railroad must be man}' hundred feet abov'e the main valley where it crosses 
the divide between the Zerafshan and the Sankar ; it descends to the Sankar across 
many of the spurs and side valleys, cutting the first and filling the second. Our 
train ran at moderate speed and we had a good sight of the cuts, whose fresh walls 
disclosed sections that are generalized in fig. 34. A somewhat uneven rock floor 
was cloaked with loess to a thickness of 10 or 15 feet. The loess contained sharply 
