'Military Report on South-West Persia, Including the Provinces of Khuzistan (Arabistan), Luristan, and Part of Fars' [‎348] (395/466)

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Band (Dam) of Ahwaz, of which advantage has been taken for the construc
tion of an artificial dam^ by which the water of the river was diverted in
ancient times from the original channel^ for the purpose of irrigating the
country to the east.
About midway between Ahwaz and Nahr Hashem, on the river Karkhah,
the sandstone hill called Jebel Mansur (Prospect Hill) is a very conspicuous
point.
On the west bank of the Karkhah the sandstone range again appears,
running in the same general direction, a few miles north of Hawiza, when it
again sinks into low undulations, which cross the Duwarij and Tib rivers, and
joins the main chain west of Deh Luran.
From actual observation of all, except the Zeitun Hills (of which,
however, there can be no question), I can certify that they are composed of the
two upper divisions of the gypsum series, namely, fine gravel, and friable, red,
calcareous sandstone; and that the persistent character of the beds continues
throughout the whole of this extended line of 500 miles.
But these outliers do not indicate the extreme western limit of the gypsum
formation; for I am convinced that, after forming a trough under the alluvial
basin of the Tigris and Euphrates, through which it occasionally appears as
islands in a shallow, the same series is continued into the deserts of the
Aneiza Bedoums; and it is probably again represented in Syria.
Section from Dizful to the Valley of Gildldhu. —Sections near Dizful
(figs. 2 & 3) exhibit the gypsum series in less broken succession than it occurs
further to the north-west.
The valley of Gilalahu presents a highly instructive section (fig. 2).
It is a denuded valley of elevation in the sandstone series, having a central
axis parallel to the main range,—namely, north-west and south-west.
On descending from the gravel cliffs which I have previously described
as intervening between Dizful and this valley, the axis of sandstone is seen
in the form of an elongated saddle, extending in a straight line down the
valley for many miles to the south-east. This axis is flanked on either side
by regular parallel ridges of similar sandstone, which slope outwards, having
abrupt and broken escarpments facing towards the axis. The extreme regu
larity of these ridges gives the valley the appearance of a well-ploughed field
on a gigantic scale. The dip near the axis is at an angle of about 25° ; but
this angle increases towards the sides of the valley, and on the south-west the
strata at length become almost vertical; and their denuded edges are covered
unconformably by horizontal limestone gravel (see fig. 2). Several patches
of gravel rest on the summit of the central axis in tabular masses; but I had
no opportunity of ascertaining whether they belong to the limestone conglo
merate already described, or whether they are merely denuded portions of a
bed intercalated between the layers of sandstone.
Beds of fine gravel frequently alternate with the sandstones here as well
as in the Hamrines and at Kasr-i-Shmn. In descending, the gravels give
place to variegated marls with crystals of selenite. The sandstone is of the
usual type; very friable, calcareous, and reddish from the abundance of
fragments of red chert. The surface of the beds is generally smooth ; but it
frequently resembles a pavement of uniform diamond-shaped blocks, separated
from each other by deep cracks. This appearance is probably due to rupture
during elevation, the fissures being subsequently filled up with a calcareous
deposit.