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0130 Explorations in Turkestan 1903 : vol.1
Explorations in Turkestan 1903 : vol.1 / Page 130 (Color Image)

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I06   EXPLORATIONS IN TURKESTAN.

A point between two bays at the west end of Issik Kul is caused by ridges of dissected conglomerates, bordered north and south by low gravel plains of gentle grade, sloping from the Chu toward the lake, and probably representing former deltas of the Chu when it flowed into Issik Kul. That it had probably once done so was recognized by Severtzof in 1867 (1875, 82). The Chu has now a silt cover on its flood plain near the lake, but shows gravels in its shoals. If the silts were laid over the plain of its former delta, they have been removed. The Kirghiz have led some small canals from the Chu eastward across the southern delta plain toward the lake. The water thus gained is distributed on fields of fine soil not far from the lake shore. A pair of whitish clay belts, about 5 feet apart, vertically, was seen contouring around the slopes that inclose this plain. We took them for shorelines at first, supposing that the clay had accumulated in the presence of reeds or grass, by which wave action was held off, as is now the case on parts of the Son Kul shoreline ; but clay belts were not seen eastward along the northern shore. These belts are probably 5o feet higher than the well-determined shorelines traced at and below the 25-foot level; moreover, similar clays in greater volume were seen at the north base of the conglomerate ridges between the two gravel delta plains, and in much greater volume farther down the Chu Valley ; so the origin of the clay belts is left in doubt.

On the north side of Issik Kul the piedmont waste slope is rather evenly developed for the first 5o miles eastward from the west end of the lake, although some local varicolored ridges rose through the waste slope at a few points where its breadth was greater than usual. For the next 20 miles, nearly to Sezanovka, the slope was often made very uneven by a succession of irregular ridges of disturbed and dissected basin deposits of variable texture. The finer sandy or silty layers here seen were frequently covered with heavy bowlders up to 8 or io feet in diameter. Some of the ridges thus formed are naturally eroded ; others have comparatively simple forms, with even scarps zoo or 30o feet high, facing the lake, in which only narrow trenches have been cut. It was evident that these ridges resulted from the recent disturbance of the earlier basin deposits.

THE PIEDMONT SLOPES AND VALLEYS.

Since the disturbance of the earlier basin deposits there has been time enough for the intermittent streams to form the newer piedmont fans and slopes of waste, which now stretch forward for from 3 to io miles with moderate declivity from the mountain base to the lake. Trains of heavy bowlders were seen on some of the fans, as if marking the paths of exceptionally heavy floods. Parts of these newer slopes are of coarse surface materials, and the subangular stones there are darkened with " desert varnish." Other parts are more gravelly and of lighter color, as if of somewhat more recent date. On both parts the scanty herbage is not always uniformly distributed, but sometimes occupies interlacing lanes, inclosing barren spaces a few feet in diameter. The delta of the Ula-khol and the abandoned delta plains of the Chu are also seemingly of modern date.

At the east end of the lake Mr. Huntington reports the occurrence of an extensive plain 4o miles broad east and west and about the saine north and south,