THE TERRACES OF SISTAN. 295
SOUTHEAST SIDE OF THE LAKE.
On the diametrically opposite side of the lake, along the southern border of the Helmund delta, a number of beaches and bluffs confirm these conclusions. Certain features stand out clearly, and may be classified according to age : (a) Modern shorelines ; (b) younger abandoned shorelines closely connected with fresh bluffs ; (c) older abandoned shorelines with weathered bluffs.
Modern shorelines.—The modern shorelines are everywhere weak, and in many places where the shore is flat and marshy they are quite indistinguishable. The lake can not have stood long at the present level, for if it had the present shorelines would be more pronounced. The water appears to have fallen gradually to its present position, as is shown by the character of the beaches which intervene between the present water-level and the i5-foot level. Where the shores are somewhat steep the weak modern beach appears as the lower member of a series of small beach ridges which culminate in the well-developed 15-foot beach. Where the shores are flat and are not closely bordered by bluffs the older beaches diverge from the present lake shore, and are more clearly differentiated.
Younger abandoned shorelines.—(z) Lutuck.—Three older beaches were seen which clearly belong to a time when the lake stood higher than now. Their exact level in reference to the water could not be ascertained, but it is certain that they lie beyond the reach of the lake to-day. In the first place, many cultivated fields, and even villages, lie between the beaches and the lake ; and, in the second place, the beaches are covered in part with large sand-dunes which could only accumulate after the water had retired. The beach which lies nearest the lake was seen at Lutuck, half-way from Devletabad to Vermal. Here the delta plain ends in low east-and-west bluffs of the the usual banded clays capped with gravel. From the foot of the bluffs what appears to be an old beach diverges northward. It has now been transformed into a strip of low sand-dunes which cover a breadth of from 25 to 5o feet, and rise to a height of 5 feet. No pebbles or fossils were found. Farther south along the base of the cliffs this beach could not be distinguished. Beyond Vermal, however, there is a strip of sand which has the character of a beach without the relief. Where an irrigation canal has been dug through this the sand was found to be full of small bivalve shells like those found in the beaches next to be described.
(2) The Seh-Kuheh beach and bluffs.—Two or three miles southeast of Seh-Kuheh and from 5 to 7 miles from the lake, there is a much better example of a shoreline of the same kind as that at Lutuck. It consists of the line of fresh bluffs from which sections M, N, and O, plate 5, were taken. At their foot lies a ridge of huge sand-dunes (fig. 170), half concealing a beach composed of sand, fine gravel, and bivalve shells like those of Vermal. About 2 miles from Seh-Kuheh the beach leaves the foot of the bluffs and runs northwestward between Seh-Kuheh and the lake. It takes the same form as the beach at Lutuck—a long line of sand blown into dunes by the wind. It is not impossible that the two beaches are of the sanie age, although I am inclined to believe that the Lutuck beach belongs to a slightly later stage of the lake's history.
The exact age of the Seh-Kuheh beach can not be determined by physiographic evidence, but it is at least evident that the water stood upon it very recently. This