File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎103v] (221/522)

2
No. 14.
Notes on the jabai Hamnn between Qarah Tappah and
Table Mountain.
Maps. —1 inch = 1 mile. T.C. 145.
T.C. 125 B.
T.C. 98 C.
AIN LAILAH PASS.
Opposite Qarah Tappah the crest of the Hamrin Range consists, not of anticlinally folded Pars
beds as it does near the Tigris, but of a scarp of the conglomeratic zone d The conglomerates
of this zone, reinforced along the main ridge by a thick band of sandstone, dip at about 5°^
towards the N.E., disappearing beneath alluvium where they are probably overlain by the clays ot
zone “ e.” On the S.W. side of the range the conglomerates are seen to overlie brown clays of
zone “ c ”, and these in turn sandstones of zone “ b,” all dipping gently and normally in a N.E.
direction.
SABALTUTAN PASS.
Over the Sabaltutan Pass the dip in the conglomerates rises to 10 , and in the sandstones to
16°, but it waves a little in the latter. Opposite Khalat al Quran it was seen that the beds described
form the N.E. limb of a N.W.—S.E. anticline, which is here pitching towards the N.W., the
crest lying very close to the road. This crest is sharp and the anticline asymmetric, the S.W.’ly
dips rising to 50° and more.
TABLE MOUNTAIN.
Opposite Mansuriyah the anticline is well exposed and pitches S.E.’wards to the small pass
over the hills, E. of the town. It rises again towards the river and probably reaches a crest-maximum
somewhere in Table Mountain ; S.E.- of Helio Hill it is seen pitching S.E.’wards. Both limbs of
the fold are represented on each bank of the river, though not much of the S.W. limb has escaped
concealment beneath the alluvium. N.E.’ly dips rise to about 18° and S.W.’ly to 90°, but there
may be slight reversal of the latter limb beneath the alluvium.
POST-TERTIARY GRAVEL.
The most interesting feature of the Table Mountain area is the post-Tertiary gravel and silt
lying unconformably upon the Tertiaries in the vicinity of the river and on both sides of it. This
gravel, which is Pleistocene or early Recent in age, is not everywhere horizontal, but has been
folded into an anticline by a Recent continuation of the folding movement which had established
the anticline in the Tertiary beds. The folding of the gravel has taken place naturally along the
same axis as the older anticline, and we have as it were an anticline of Pleistocene or Recent Gravels
capping a sharper anticline of Tertiary sandstones (see section). The maximum dips in the limbs
of the two folds are :—
Anticline of Tertiary beds
Anticline ol post-Tertiary beds,
f S.W. flank
IN.E. „
IS.W. „
(N.E. „
vertical.
20 °.
22 °.
3°—4°.
The S.W. ly dip in the gravel is quite distinct, and the beds can be seen arching over towards the
crest. The N.E. ly dip is only apparent in the general steady slope of the gravel plateau level.
Since the deposition of the gravel, therefore, the S.W. limb of the anticline of Tertiaries has been
steepened 22 and the N.E. limb 3 or 4 , in other words the fold has been tightened or compressed
to the extent of about 25 .
POSSIBILITIES OF OIL.
Natmal occuiaences of petroleum or sulphuretted hydrogen in the area under report, were
neither noticed nor heard of. The anticline is intact and not too acutely folded, and there is an
inconspicuous surface indication of sulphuretted hydrogen and petroleum in the anticline adjoining
N.E. die Jabai Gilabat , this indication is 28 miles distant from Table Mountain, but not more than
12 miles from the axis of the Jabai Hamrin anticline. It is true that the presence of subterranean
oil-bearing strata is usually shown at the surface by seepages, but in this case any petroliferous beds
would be below a gieat depth of rocks, the bulk of which would consist of clays belonging to zone
a . No fault was seen up which oil might seep, but the presence of selenite at the surface along
the crestal area seems to indicate that the clays have been cracked transversely or at any rate form
a cap not sufficiently impervious to prevent the upward percolation of gypseous water from the
Fars below Such radial cracking along the crest of an anticline is common and natural, the small
upright cracks being filled with calcite, gypsum, mud, etc. I have seen less promising areas than this
tested iii Burma. Dn ling in this area would have to be deep and would be a pure gamble until
more is known of the general he” of the oil supplies in the country and also until the Jabai
Hamrin itself has been more extensively examined.
Dated 20lh April, 1919.
E. H. PASCOE, Supdt.,
Geol. Sur., India.

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