‘1 Diagrammatic Section N. of the Tuz Khurmatu’ [‎183v] (2/2)

t
4
These wells are situated along the line of a small subsidiary anticline occurring in the N E
flank of the main fold. This small fold, like the main anticline is isoclinal and itself slightly con
torted ; near the wells it has been bent bodily backwards by its contact with the similarly bent
main fold in the way depicted. Extending parallel to the line of wells and a few yards N E of
them is a double o ridge of limestone with a local strike of 55 J W. of N—55° E. of S. and a din
E.N.E. of 50 o -60°, which probably represents the core of this fold. This limestone is flanked on
both sides by white gypsum succeeded by red and green clays belonging to the uppermost horizons
of the Ears. To the S.W. these red and green clays form a small syncline, along which flows a
straight N.W.—S.E. reach of the stream, and which separates the subsidiary from the main
anticline, which is contorted in a way similiar to that sketched. This interesting minor anticline
can be traced for two miles or so to the N.W., the limestone and gypsum pitching underneath the
red and green clays, and shewing the remains of an acute arch. When traced S.E’wards the
minor anticline is no longer recognisable after li miles ; in pitching it loses the bent backwards and
assumes a normal overfolded condition as shewn in Fig. 3. The small syncline when traced in the
same direction widens, and includes their sandstones which are referable to the lowest horizons of
the Red Clay and Sandstone Series ; it also becomes normally underfolded in correspondence with
the anticline.
Leaving the oil-well locality and proceeding S.Edwards, we find the same baffling persistent
gentle N.Edly dip in the outward face of the hills,, with here and there contortion, but no defi
nite relics of a crest. Between the sulphur spring of Gharrah and the Kurah Chai the Ears outcrop
becomes very narrow and the beds along the alluvial boundary are almost horizontal.
In the Red Clay and Sandstone Series forming the N.-E. limb, considerable variation in dip
may take place along the strike, causing a widening or narrowing of the outcrop of its zones ; N.E.
of Palkanah a small subsidiary anticline can be seen. As in other areas, we find the same curiously
rapid erection of the beds on approaching the Ears boundary. Take the section opposite Albu
Sabah from N.E. to S.W. In the Conglomeratic Stage the N.E/ly dip is quite gentle. Passing
down into zone c it averages abuut 40°. In zone u b ” there is a gradual drop from 45° to
about 15. ^ In zone a” it sinks as low ^as 10°, but within 200 yards of the Ears boundary it has
risen to 30 and at the boundary is 40°, while a little way inside the boundary it becomes 75°.
There are more causes than one which may have individually or collectively been responsible for
this ridging up of the Ears outcrop. The primary cause is no doubt the resistance to the thrust,
but the localization of this erection may have been to some extent also due to (/) the great plasticity
we t gypsum sediments, (it) a premature folding movement before or during the deposition of the
Red Clay and Sandstone Series, especially of its lowest zones, (m) denudation accompanying a folding
movement and lightening the burden over the anticlinal crest.
Besides the main reversed fault along the S.W. Ears boundary, other reversed strike faults are
not uncommon within the Ears outcrop. Some of these can be well seen in the sections of the
Aq Su and the Kifri stream.
T
PETROLEUM.
fij Natural Indications .—Due E. of Tuz Khurmatu, close to one of the places where an
arching over of strata was observed, is an emanation of hydrogen sulphide in a small stream ; the
actual source of the gas was not found, but it is probably associated with the usual bituminous
earth. Some 2\ miles further down, also near a crestal structure, is another occurrence of the
same kind.
The locality of Palkanah (Abu Sarkal) opposite Suleiman Beg, and commonly spoken of as the
Tuz Khurmatu Oil locality", has been known for a long time. The so-called wells are large pits dug
piesumably upon natural seepages, and lying upon a line very close to and, as I have observed,
probably a few y r ards S.W. of the axial plain of an isoclinal subsidiary^ fold occurring in the N.E.
flank of the main anticline. The oil is the usual black tarry material smelling of sulphuretted
hydrogen and accompanied by r sulphur-laden water. It has already been reported on by the Anglo-
Peisian Oil Co. s chemists. At present some 14 pits are being worked, yielding between 240 and
280 gallons of crude oil a day, one well producing more than the other thirteen. It is carried
on the backs of donkeym and mules to Tuz Khurmatu where it is subjected to a crude distillation in
5 oi 6 stills, each consisting of a retort and spiral condenser. The two extreme wells on the line
are a, little under a mile apart, but further S.E there is a little bituminous gypsum in one spot
and in another an emanation of sulphuretted hydrogen accompanied by bituminous earth. Oil
indications are by no means confined to the subsidiary fold, but are found in the main anticline,
"where outcropping bands of gypsum and limestone are seen to be bituminous for many yards in
the S.W face of the hills in the vicinity of the gorge.