الملف ١٤٥٠\١٩١٩ "بلاد الرافدين وكردستان: تقارير جيولوجية عنها" [و‎‎١‎٨‎٢] (٥٢٢/٣٨٦)

I I —I I iTriL ^’! cU. l ! l J. 1 U«BBE3Ba
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No. 10.
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Notes on the Geology of the Country between Tazah
Khurmatu and Tauq.
Maps. —1 inch = 1 mile. T.C. 252 (allusions to T.C. 253 and T.C. 211.)
INTRODUCTION.
There is nothing of direct economic importance in this report. But indirectly, being a
description of yet another anticline, and one of some interest, it is a further contribution to the study
of local structural detail so intimately connected with the natural storage of oil. Very bad weather
and the consequent death of two camels delayed work in this area.
TAZAH KHURMATU AREA.
East of Tazah Khurmatu an anticline pitching gently in a N. N. W. direction is seen, exposing
the Red Clay and Sandstone Series only. Both stages are present and the boundary line between
them, which is somewhat difficult to fix, has been drawn swinging round a little short of the
Tauqmaqil Chai. The Lower Stage consists of the usual sandstone and clays of the middle horizons
and the light brown clays characterising the highest horizons. The latter pass up into the Upper
Stage which contains the usual soft conglomerates, and thick brown clays. The same thick
conglomerate, noticed in other areas, produces a similar long, monotonous, level range of hills, in
this case known as the Matarah Dagh. N. of Tazah this conglomerate swings round in a horseshoe,
forming the Sareh Tappah. Further N. on the other side of the Qazah Chai we find some of the
youngest Tertiary beds hitherto met with. They form part of the Conglomerate Stage, consisting
of light brown or pinkish clays with thin infrequent conglomerates or gravels, and occasional
layers of current-bedded sand-rock.
TAUQ AREA.
South-eastwards the anticline becomes overfolded, and N. E. of Tauq fold-faulted. In this
interesting area, S. of Tauq Bridge, a traverse from N. E. to S. W. shews the following sequence.
The Lower Stage of the Red Clay and Sandstone Series is present in a normal way, its middle
horizons consisting of the usual rapid alternations of massive sandstones and clay bands, producing
the characteristic system of parallel ridges and valleys ; these pass down into the lower horizons
consisting of thick masses of red clay which, however, produce more prominent topography than
usual on account of the presence in them of numerous thin layers of more sandy material, both
clay and sandstone being deeply iron-stained. These beds overlie gypsum limestone and clay
bands of the Ears, dipping at the same angle, viz., 30° in a N. W. direction. At its S. W. boundary,
however, the Ears is not in contact with these red clays and thin sandy partings, but with the
massive sandstone bands belonging to the middle horizons of the Lower Stage of the Red Clay and
Sandstone Series. The lower horizons are missing and the boundary is a reversed fault. The
reversed dip in these massive sandstones rapidly steepens till the beds become vertical, and then
dip S. W.’wards in the normal direction at angles which rapidly decrease. A few thin gravel
partings are seen in these sandstones just before they pass up into the light brown clay zone ;
the latter, in turn, passes up into the Conglomeratic Stage, forming the low mound-like hills S. E.
of Chavirgah. The reversed fault soon becomes hidden by alluvium to the S. E. N. of the Tauq
Chai, the outcrop of the Ears continues for about half a mile and then ceases ; its dip is generally
26° in a N. E. direction, but the river section shews there is some contortion. At the extremity of
the outcrop, owing to the intervening fault, there is no swinging round of the Red Clay and
Sandstone beds from one flank (o the other, as there would be in a normal pitching anticline.
Here also the lower horizons of the Red Clay and Sandstone Series are missing on the S. W. and the
Conglomeratic Stage approaches still nearer the Tars. There are no clear sections in this
Conglomeratic Stage, but, from the shape of the hills and the distribution of gravel over their tops,
the boundary line has been drawn as indicated ; the W. part of the hills consists, as would be
expected, of massive light brown clay. The fault, therefore, probably extends for some distance
N. W.’wards, the displacement or throw apparently being greater N. of the Tauq Chai than to the
S. As a rule the displacement of a fold-fault is greatest in the more central parts of an anticline,
but in this case, perhaps owing to curvature of the fold axis, it is greater along the pitch of the
anticline. I say ‘.'perhaps owing to curvature of the fold axis,’ for it is not easy to distinguish
between cause and effect ; it could just as rightly be stated that the convexity of the fold axis
N. N. E. of Tauq is due to greater displacement along the fault. The low mound-like hills of the
Conglomerate Stage S, of Chavirgah curve curiously towards the S. S. W., but I came across no
sections shewing to what this is due.
E. H. PASCOE, Supdt.,
Geol. Sur. y India.
Dated 11th March, 1919.