232 TIIK HASIN OF ICASTERN PERSIA AND SISTAN. 
playa " of Khaf (B, fig. 152), at the center of an important subsidiarj' basin. Farther 
south a steep east-facing escarpment, which suggests a fauU scarp, limits the Persian 
basin, which stretches away in normal fashion westward from the summit, while on 
the east, at the foot of the escarpment, the smooth " Desert of Despair " (C, fig. 152), 
strangely broken by buried mountains, spreads its harsh gravels far southward to 
the lake and swamp of Sistan (D, fig. 152). Onward in the same direction the 
desert continues to the swamp of Ma.shkel (E, fig. 152), still bounded by the escarp- 
ment which swings somewhat eastward south of Sistan and bears upon its top the 
cone of Kuh-i-Taftan (O, fig. 152), the only active volcano of Western Asia. South 
of all these features the low mountains of southwestern Haluchistan bring the 
depression to an end (F, fig. 152). The streams flowing into the depression from 
the east are long and large ; those from the west are so short as to be little more 
than mountain torrents. 
GEOLOGICAL HISTORY OF THE B.\SIN. 
The age of the basins of Iran can onl\- Ik- determined by a stud\- of the geology 
of the countr)', but of this, unfortunately, we know merely the bare outlines. Not 
only is the country remote and difficult of access, but the aridity obliges the traveler 
to hold closely to the roads which usually traverse the gravel-strewn plains. If he 
makes detours to the moinitains, his caravan may be obliged to spend the night 
without water. Geological study is at a disadvantage. The work of Blanford 
(A, p. 468) and the geographical map of Mushketoff show that the mountains 
bordering the Persian portion of Iran consist for the most part of a main mass of 
Cretaceous limestone bordered on the inside by a smaller amount of Paleozoic or 
ancient cr>-stalline strata, and on the outside by concentric bands of Tertiary strata, 
each of which is less warped than the one below it. The inference is that at the 
end of the Cretaceous era the mountain borders of western Iran began to ri.se and 
have continued to be uplifted throughout a large part of Tertiary time. Throughout 
the Kocene period the sea (Hlanford, A, p. 468, and Vredenburg, p. 168) covered 
the region which is now occupied by the low mountains of Baluchistan, and also 
nuich of the interior, judging from the nummulitic limestone which Blanford 
mentions as being reported from Yezd and Kohnul, and which I fomid abundantly 
in the mountains northwest of Sistan. It also probably covered the northwestern 
corner of Afghanistan, for the mountains there consist largely of Tertiar\- forma- 
tions which seem to be of rather late date. Apparently there was oceanic connection 
between the Arabian Sea and the Samartian vSea which covered the Caspian region, 
and the interior of the Iran basin was covered by a marine embayment. When or 
how the sea retreated or when the eastern borders of Iran were uplifted we do not 
know. It is clear, however, that during the latter half of tlie Tertiary era Iran 
had been divided into basins in which subaerial deposition took jilace, as is shown 
b)- the silty and sandy strata of a prevailingly red color which overlie more uni- 
fonnly bedded shales of marine or estuarine origin. 
