File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎97r] (208/522)

Report No. 9.
Oil in the Kirkuk Anticline.
Maps.— 1 inch equal to 1 mile. T.C. 253
I inch equal to 1 mile. T.C. 172.
INTRODUCTION.
Since one hank of this anticline is almost entirely concealed beneath the Alluvium and anything
in the nature of an arch or anticlinal crest is seen in a few places only, the precise condition of the
fold is largely a matter of speculation. A long narrow outcrop of Lower Pars beds extends in a
general N.-W.—S.-E. direction through the eastern outskirts of the town of Kirkuk. N.-W.\vards
it reaches the village of Amshahr, beyond which an outcrop of Lower Pars beds along the same
line of folding reaches and probably crosses the Lesser Zab ; S.-E.’wards the outcrop was traced
as fai as the latitude of Panj Ali. The dip with few exceptions is N.-E.’ly and from moderate to
steep. On the N.-E. the outcrop is succeeded in a normal way by the Lower Stage of the Red
Clays and Sandstones, and this in turn by the Upper or Conglomeratic Stage ; to the S.-W. the
succession is obscured by Alluvium except in two or three places. The clearest section is seen E.
of Panj Ali, where the Low'er Pars is succeeded on both sides by Red Clays belonging to the
lowest horizons of the Red Clay and Sandstone series. The structure is here seen to be that of
an isocline overfolded towards the S.-W. N.-W. of this area the anticlinal nature of the outcrop
is sm mised rather than proved. The tightness of the folding indicates a closer proximity to the
origin of the folding movement which proceeded from the N.-E.
ROCKS.
Loiver Fars. 1 he Lower Pars consists of the usual sequence of gypsum, limestone and clays.
Amongst the limestones is the noticeable pelecypod bed, an old shell bank crowded with small
pelecypods, and having a superficial resemblance to a nummulitic limestone. Bright Red Clays
are especially prominent in the neighbourhood of Kirkuk. The uppermost bed is sometimes a
gypsum band, sometimes a fossiliferous limestone ; a little below is a thin layer of reddish sandstone
similar to that of the succeeding series.
Red Clay and Sandstone Series .—The Lower Stage of the Red Clay and Sandstone series
consists of the usual Red Clays and current-bedded sandstones, the former predominating near
the base and producing flatter and more rounded topography, the latter increasing upwards and
producing the series of characteristic ridges indicated on the map. Thick beds of light reddish
clay again appear in this stage, however, as it passes up into the Upper or Conglomerate Stage. In
the latter, purlish or yellowish red clays are prominent, the colour being less intense than that
of the earlier argillaceous deposits. The boundary line between the two stages is the base of the
first thick Conglomerate, which produces outstanding physical features in the form of a line of
loftier round-topped ridges. It is an artificial boundary since thin inconstant Conglomerates occur
below it, but it has been selected as being easy to identify and map. Deposition has been
uninterrupted from the Lower to the Upper Stage. The most prominent Conglomerate forms a
curiously regular even range, extending with scarcely a break for a great many miles, and
providing many streams of excellent water on both sides, at any rate during the winter months.
As the map shews, the Lesser Zab and the Qarah Chai are the only two streams which pierce the
part of this range, under description, which is known variously as the Shamasin Dagh, the
Baba Gurgur, and the Jab-el-Buar. Its sky-line is a monotonous, almost unbroken, slightly
denticulate line, and its dip-slope presents such a characteristic appearance of intricate dissection
combined with rounded outlines—due to the easy disintegration of the Conglomerates and the soft,
interbedded clay bands—as to be recognizable many miles distant. N.-E.’wards it is covered by
high-lying Alluvium.
The thickness of the Lower Stage opposite Panj Ali, works out at over 7,000 feet. The
thickness of the whole series must be over 12,000 feet, a river deposit rivalling in size, as it
resembles in character and age, the great Siwalik deposit of India-
Mesopotamian Alluvium .—As in former maps the boundary of the Alluvium indicated is merely
the approximate limit of Tertiary exposures, and has no tectonic significance.
STRUCTURE.
m
It will be advisable to consider first the Panj Ali area in the extreme South; where the structure
is clearer, and proceed thence N.-W.’wards, examining these more obscure portions in the light
of the more complete succession in the S.-E.
In the Panj Ali area reviewing the section from N.-E. to S.-W., the Conglomeratic Stage on
the N.-E. flank of the anticline passes do^wn into the Lower Stage of the Red Clays and Sandstones
dipping at angles varying between 40° and 50° ; approaching the Lower Fars, however, the dip
diminishes gradually to 35° and 30° ; and then rapidly steepens to 50° and 60°. The dip along
the N.-E. fringe of the Lower Fars outcrop is here about 60° ; this is followed by minor puckering
and contortion, but a distinct arch of rather more importance than those of the puckers can be
made out along the centre of the outcrop, and, from all appearances, may be accepted as the crest
of the main anticline. Further to the S.-W. vertical dips and further contortion follow, until the
boundary between the Lower Fars and the Red Clay and Sandstone series is reached. Here the

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