الملف ١٤٥٠\١٩١٩ "بلاد الرافدين وكردستان: تقارير جيولوجية عنها" [و‎‎٢‎١‎٩] (٥٢٢/٤٦٨)

5
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Odd Notes on the Country
between Tikrit and the Jabal-Hamrin
and Jabal Makhul.
ALLUVIA.
The river Tigris flows through a belt of some three miles wide of very recent low-lying alluvium.
This is naturally less salt and much less permeated with gypsum, and is largely under cultivation.
It is flanked on both sides by slightly older alluvium, which forms the rolling plains of Mesopotamia.
It is more sandy than that around Baghdad and, N. of Tikrit. is practically unstratified and strongly
impregnated with gypsum ; some of our deep trenches show in what a large proportion this mineral
is present, not only filling small veins and fissures, but impregnating the silt itself. Elsewhere, such
as to the S. of the Jabal-Hamrin this alluvium is stratified. Close to the river and over soft Tertiary
conglomerates which crop out occasionally, it includes beds of gravel which occur in the pockety
way so characteristic of this form of deposit ; the gravel reaches thicknesses of 20—25 feet, and more
often than not is overlain by sandy silt. A few feet of Ears beds including a gypseous fossiliferous
marl are exposed in the cliffs at Tikrit, overlain by a current-bedded sand-rock belonging to a Sand
stone Series to which I shall refer to later on, and which may be classed provisionally as Bakhtiari.
The junction of this series with the Ears seems, in fact, to be exposed here : the exposure, however,
is very small and obscure, and has not been coloured on the map. Similar exposures of one or both
of these series will no doubt be found in other places, especially along the river cliffs and in some of
the deeper stream-courses. The alluvium is pebbley for miles inland, the pebbles being derived
from underlying conglomerates belonging to the above-mentioned Sandstone Series.
ROAD METAL.
The pebbles of the gravel range up to 8 or 9 inches across, the vast majority consisting of
siliceous material, chert, siliceous sandstone, milky quartz, etc. ; the only other noticeable pebbles
are those of an igneous greenstone, rare pieces of homogeneous grey limestone possibly derived from
Eocene rocks, and occasionally pieces of black pumice. This gravel—especially the coarser
varieties—broken up into angular fragments, would provide road-metal of a high quality. Probably
it is already being used for such a purpose. No doubt it occurs lower down the river, nearer
Baghdad, and would vastly improve the roads of this city.
TREES.
The absence of trees in Mesopotamia is, I think, not attributable to thriftless cutting down of
timber in former times, since—on the authority of Herodotus if I remember rightly—the
Mesopotamian plain has always been practically treeless, but is the result of the impregnation of the
soil with the salt and gypsum derived from the Ears rocks which lie not very far below the greater
part of the area. Whether any serious effort to grow trees has ever been made, however, seems
doubtful, for there should be a good chance of getting suitable trees to flourish along the river banks
and along any net-work of irrigation canals that may be constructed. I noticed bushes of the Wild
Plum (Zizyfihus Jujuba) near Baiji, and trees like Acacia Catechnoides or Acacia Ferruginea, although
not producing much in the way of timber, would probably contrive to exist, as they do in similar
regions in Burma and India, and would at least provide fuel, and form a humus for other trees.
Local patches of soil there must be practically free from salt and gypsum, such as that around Kut.
The neutralisation of the effects of these salts—magnesium sulphate, sodium sulphate, calcium
sulphate, sodium chloride, etc.—is the serious problem before the agriculturist of this country,
especially north of the deltaic area.
WATER.
The prospects of obtaining sweet water by boring in the plain between Tikrit and the Jabal-
Hamrin and Jabal-Makhul are not easy to diagnose. There is such a large element of chance as to
the water being sweet or brackish that a geologist can offer no very definite advice. The Red Clay
and Sandstone Series (? Bakhtiari) flank the Jabal-Hamrin and Jabal-Makhul, and since it is probably
a fluviatile deposit, it is not at all impossible that its upper strata, consisting of loose conglomerates
and sandstones, may contain water which has been protected from the saliferous Ears beds beneath
by some impermeable band of clay ; thick bands of somewhat sandy clay do occur at the base of
this Sandstone Series. The probability is that this series underlies the alluvium over large areas,
especially areas not very far from the ranges and parallel to them. The chances of reaching this
series with the drill by piercing the alluvium and obtaining potable water, at say 5 or 10 miles from
the ranges, are not unreasonable. Near Tikrit the chances are against the water being sweet, since
the Lower Ears is probably very close beneath and the Alluvium full of gypsum.
To exemplify how purely a matter of chance it is, the Ain Khalid and Ain Mukhailah springs
may be mentioned ; these occur close to the upper boundary of the Lower Ears itself in the Jabal-
Hamrin, more than half of which range consists of gypsum. The water is slightly blackish and is
drinkable to people accustomed to the small amount of sulphate present ; to those unaccustomed it
is not harmful but has the effect of minute doses of Epsom Salts.
If it is not desired to penetrate completely the Alluvium, visible stream-couises aie preferable
sites usually for such shallow wells, since there is a considerable amount of underground drainage
in the plains, and this would naturally tend to follow established lines.
E. H. PASCOE,
5th Dec., 1918.
S.G.P.Bd —1819-2653—200-15-1-19.