File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎235v] (501/522)

2
The Bakhtiari Series in the Bakhtiari country is a thick deposit of sand
stones and shales passing up nto coarse conglomerates with highly calcareous
matrices, and lying unconformably on the Upper Bars Group.
In the district under consideration the typical conglomerates were not
observed. The Series is represented by loosely compacted sandstones with shales
and clays, indistinguishable from the Upper x'ars locks, except for occasional
conglomeratic bands. While there is every appearance of conformity it is not
impossible that these beds lie disconformably on the Upper Bars rocks. On the
other hand it should be borne in mind that all sedimentaries are lenticular in a
greater or less measure, and that not only may the material for the formation of
typical conglomerates have been absent here, but also tnat the post-Miocene dias-
trophism causing the unconformity in tne Bakhtiari country may have been
contemporaneous with a continuous period of deposition and subsidence here.
The KoyvEit Series, so named from its development N.YU of Koweit, is a
shallow marine deposit of thick gypsum bands, loosely compacted sandstones or
sands, and clays, and sandy clays containing more or less gypsum.^ The Series is
of early Pliocene or possibly Pleistocene age and unaffected by folding movements.
It attains a thickness of not less than 400 feet near Koweit, but near Baghdad
thicknesses greater than 75 feet are not actually visible, though doubtless existing.
Between Ramadi and Hit He Series undergoes a marked lithological change.
The bands of pure gypsum which at Ramadi attain a thickness of a few inches
only, are at Hit 12 feet thick, and reminiscent of the Lower Bars gypsum. At
Hit, however, not more than 150 feet thickness of these beds exist, and they lie
disconformably on the Euphrates limestone.
The Mesopotamian Alluvium is due to deposition from the Tigris and
Euphrates Rivers. It consists mainly of clays with sands and occasional line
gravels, and may be observed increasing in area every year at the mouth of the
Shatt-el-Arab. Basrah was a seaport in historical times.
At Amara, a well, put down for water passed through the Alluvium at 120
feet (or 112 feet), while another at Shaiba, near Basrah, was still in alluvium at
250 feet.
(4.) TECTONICS.
In the West all the strata are lying horizontal. The Euphrates limestone
has been subject to movements of elevation and depression, but the region of Hit
is characterised by the lack of any tangential pressure, which would have
produced folding.
In the East, however, i.e., E. of the Diyalah River, the country is thrown
into a series of parallel anticlinal folds with the steep flanks towards the SAY.
They increase in intensity towards the hills, and exhibit in this direction a
regularly increasing hade or angle of departure of the axial plane from the
vertical.
The Lower Bars rocks are first brought to the surface at Naft Khana, where
they form the core of the Na.ft Khana anticline. The Dynamics of the Gypsum
Group of Persia is remarkable; the two controlling factors are its inherent
inability to withstand stress coupled with a stratigraphical position between
rocks of a relatively highly resistant nature. The result is, that when the gypsum
is exposed, or, in other words, where it has lost the bracing effect of the overlying
strata, it behaves like a plastic material and folds isoclinaily, overfolds and faults
to a marked degree.
At Naft Khana a few hundred feet only of Lower Bars strata are exposed,
yet the tangential pressure has at once been relieved by the gypsum breaking
down under tensile stress, along or near the axial plane of the fold, and forming a
reversed strike fault. This fault is of a minor and purely local nature, as is
evident from the map, and its throw is of not more than a few hundred feet.
(5.) EVIDENCE OB PETROLEUM.
(a.) Ramadi—Hit District..
At a distance of 32 mips W., 25 S. from Ramadi on the S. side of the
Euphrates is the pitch lake of Abu Jir.
It is an impressive feature in the desert, being nearly a mile in length and
of an area of some 200 acres. The pitch emanates from five main seepages, iu
the form of. a viscid bituminous oil accompanied by petroleum gas and
sulphurous water. Evidently in the hot weather the bitumen softens sufficiently

File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎235v] (501/522)

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File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎235v] (501/522)

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