File 1450/1919 ‘Mesopotamia & Kurdistan: Geological Reports on’ [‎125v] (265/522)

2
proportion of limestone is not much different to that m the Oaiyarah anticline. 1 o the north and west
of the latter place the amount of limestone increases ; in the J. Najmah two thick bands of type “b”
appear and these we have correlated with the Mishraq limestone of further north. At the same
time limestone D. which at Oaiyarah did not exceed 4 feet swells out to 10 feet. In the Mishraq
and Araij areas and north of that the Mishraq limestone has to a large extent determined the
scenery as it crops out over large areas. It does not resist weathering itself nor does it protect
the underlying beds, as does a limestone of type “ a ” and as a result it is now strewn in blocks far
beyond its outcrop.
From Qaiyarah northward the thickness and number of the marl beds is decreasing and it is
probable that they are replaced by limestone.
At Fathah the lowest beds yet seen crop out in the river and can now be examined as the river
is low Three beds of peculiar composition associated with marl and gypsum occur in a small dome.
These beds are called provisionally limestone and appear to consist chiefly of arragonite ; they are
very porous and cavernous and have a peculiar banded appearance. They are soaked in oil which
makes it difficult to determine their composition and origin. They certainly appear to be inter-
bedded as in one place a very fossiliferous Lower Fars limestone of type “ a ” was found underlying
one of these bands. A detailed examination of this section on the scale of 6 inches to the mile will
be made shortly and it is hoped that some light will be thrown on the mode of occurrence of the
oil.
In the anticlinal areas varying thicknesses of the Lower Fars are exposed by denudation ; in
the J Hamrin and J. Makhul some 600 feet and in J. Khanuqah considerably less. In the Huwaish
anticline only the top of the series is exposed. In J. Qaiyarah about 500 feet, whilst in J. Najmah
about 300 feet. In J. Mishraq and the country to the north as far as Mosul not more than 400 feet
are exposed.
In the Oaiyarah report we accepted for the thickness of the series the figure given by Porro
and Kissling in the section seen by them in the Kara Chaugh hills namely 250 metres. In view of
the unreliability of their observations we are now unable to accept this even as a rough estimate. In
North Persia in the neighbourhood of Oufaitu it has been estimated as 2,500—o,000 feet thick. In
the Euphrates valley our impression is that it is not more than 1,000 feet thick. We consider it
probable that in the Tigris region it will be thicker than in the Euphrates valley and not as thick as
in Persia and would take 1,500 feet as a likely estimate of the thickness. W e shall examine the
Kara Chaugh section in the near future with a view to getting an accurate measurement of the
thickness.
In the northern part of the area some sandstone bands appear in the upper part of the series.
At Hammam Ali near the sulphur springs and seepages a green argillaceous sandstone crops out in
the river bank and this we believe to come very near the top of the series.
Upper Fars.
Throughout the area the nature of the Upper Fars does not vary materially. 1 he lower pait
of the series consists of red marls and sandstones with some green marls, particularly near the base.
The Upper part is characterized by greenish friable sandstones in thick beds ; it is only lound in
one or two areas, e.g., Sharqat and on each side of Oaiyarah. In general one may say that the beds
of the lower part of the series are predominantly red and those of the upper part greenish-gie\ .
Gypsum is noticeably absent and only occurs as veins in one or two places. This series always
occurs in synclines and the fact that only a small amount of the upper part crops out indicates that
these synclines are shallow. In most cases the dip at the junction with the Lower bars is steep
usually not less than 30 deg., but this flattens out within a few hundred yards and the beds become
approximately horizontal.
We have still no evidence for an uncomformity between the Upper and Lower Fars in fact
everything points to complete comformity. The sudden lithological change indicated by the entire
absence of primary gypsum in the Upper Fars suggests unconformity but until actual transgression
is found the two series must be considered as conformable.
Gravel.—Coarse gravels occur at many places at various heights above the river. They consist
of large pebbles of sandstone, quartzite (remarkably like the Bunter pebbles of England) limestone,
chert and some igneous rocks. In many cases there is a hard calcareous cement and even some
of the obviouly new gravels are cemented. All gravels seen can be considered as belonging to
the Tigris drainage system.
Alluvium .—Large alluvival plains are found in various parts of the Tigris valley and obscme
much of the structure. A form of alluvium is found in many places in the Upper Fars outcrop along
the courses of the larger “ wadis it consists of a wash formed from the Upper Fars marls anc
attains a thickness of 30 feet in places.
(4) SEEPAGES SULPHUR, Etc.
In the Tigris valley a number of seepages of oil or bitumen have been known for a long time
A certain number of small seepages have come to light within the last year or two : Dr. ascoe, in
his reports on this district records several new ones and we have located two which hac n
previously been noted. It is quite likely that there are others in lesser known parts ot the coun i>,
as attention would not be called to them unless they were of sufficient size for the At a ° ^
bitumen for their camels and for other purposes, Starting from the south none are known nn
Fathah is reached :—
(1) Fathah.
At the place where the Tigris cuts through the J. Hamrin, oil seeps up m the river and aPP e .a|J
as spots on the water when the river is high ; now that it is low the actual outcrop ot the oil Peaim.