256 THE BASIN OF EASTERN PERSIA AND SISTAN. 
better, gravel, forniiiit:^ an unconsolidated sheet some 40 or 50 feet thick, which lies 
unconfoTuiably on the beveled edges of the other strata and shows almost no sign 
of warping. It seems probable, howe\-er, that the gra\el sheet has been uplifted 
and tilted somewhat, and that it rejiresents the old piedmont deposit of a time pre- 
vious to the faulting and ui)lift of the Anau and Suru-Muzdar blocks. On the east 
this conglomerate or, belter, gravel, forms a smooth though slojjing plain, in which 
are incised young valleys ; on the west it has been dissected into low, rolling hills. 
Thus far there can be but little question as to the true nature and origin of the 
phenomena of the gorge ; it is when we come to the terraces that the difficidty 
begins. In its more open portions to the north of the hard limestone the sides of 
the gorge are marked by well-defined gravel terraces to the number of five, which 
gradually converge downstream until the}', as well as the upper grade plain, merge 
into the general slope of the present piedmont plain in the vicinity of Anau, where 
the stream comes to an end. The heights of the terraces above the stream, as 
measured at a point well within the gorge a little below the so-called "Old Mills," 
are approximately as follows : 
Keet. 
First terrace, narrow and insignificant 3 
Second terrace, rather broad and strong 6 
Third terrace, broad plain of main valley floor 20 
Fourth terrace, narrow, often missing 50 
Fifth terrace, broad and flat 100 
Grade plain, uplifted piedmont deposit 300 
The whole number of terraces is not always present, sometimes one and some- 
times another being undercut ; nor does it appear as though they all merged into 
the plain at the same point. 
If all the terraces were cut in the solid rock, and came to an end in the Anau 
fault block, it would be easy to explain them as the product of the same faulting 
which produced the block and which uplifted the old piedmont plain. As a matter 
of fact, however, the lower terraces at least, so far as their structure could be made 
out, seem to be composed entirely of stream-laid gravel. In other words, the gorge 
was cut to nearly its present form and then was subjected to a series of changes by 
which it was first filled with gravel and then cut out again. Moreover, although 
the terraces disappear in the narrowest portion of the gorge, three of them reappear 
in the more open jxjrtion of the valley farther upstream — another evidence that the 
younger ones are of later date than the gorge. The importance of the relative ages 
of the gorge and the terraces lies in the fact that the fault which caused the cutting 
of the gorge represents the last mo\-ement of uplift of which we have any unmis- 
takable record. It is not impo.ssible that the terraces are due to earth movements 
of a kind which first caused deposition and then erosion, this alternation being 
repeated as many times as there are separate gravel deposits, an unknown quantity 
which may number from one to five. The Anau terraces, like those described by 
Professor Davis, are uusatisfacton,-, because, so far as can be seen, thej- may be 
either tectonic or climatic in origin. 
At Anau, and elsewhere along the base of the moimtains as far as Dushak, 
where the railroad turns to the northeast, the hasty view of the country- obtained 
