142 EXPLORATIONS IN TURKESTAN. 
that thickness of sediments disturbed by the advancing later moraine predates that 
advance; (3) that the shore of a saline lake has retreated from about the 150-foot 
level to its present position since the maximum of the overriding moraine ; (4) that 
too little time has elapsed for much alteration either by solution or weathering of 
the salt growths since the lake-shore existed at that height ; (5) that it seems prob- 
able that the flexibility exhibited by the pushed-up sediments during the advance 
was due to their being well soaked under water. This might indicate that the lake 
was not only there after the overriding moraine had come to rest, but possibly also 
during the advance, and soaked the otherwise brittle sediments into a flexible state. 
We have seen that the Kara Kul sediments consist chiefly of the finest blue- 
gray clays, containing small flakes of mica and occasional small angular fragments 
of stone. The light blue-gray color is, in itself, remarkable, for all fine material 
brought down from the mountains to-day seems to be red. This shows that the 
old Kara Kul sediments are not oxidized, as are the deposits of to-day, and that 
Fig. 107. — Looking north from the front of the Kara Jilga Moraine to the Kizil Kul Steppe. 
the)- are in all probability a product of glacial grinding ; their thickness \-aries with 
the topography of the underljing old moraine. One minimum estimate gave a 
thickness of 40 feet where the wall, 30 feet high, of the elliptical lake described 
was seen through the clear water at least 10 feet below the surface. How much 
deeper the sediments continued could not be estimated. All this accumulation must 
have taken place since the maximum ad\-ance attained by the old underlying 
moraine. This, together with the width of the channel established b)' the Kok-sai 
dar)-a, is good indication of the antiquity of the underlying moraine. 
The kettle-hole topography of the overriding moraines, and the narrow 
V-shape of valleys cut in them, with the torrent condition of streams contained, 
show what a relatively short time has elapsed since they were formed. 
THE KARA JILGA MORAINE. 
It will be seen on the map that the Kara Jilga darja turns an acute angle at 
about 10 \ersts upstream from its mouth in Kara Kul, and now remains, partially 
filling the deep valley between this little lake and the angle of the Kara Jilga. Its 
surface is indented with frequent kettle-holes, and its topograph}- is, in general, very 
