'IRAQ AND THE PERSIAN GULF' [‎392r] (786/862)

STRATIGRAPHY
Age
Formation
Remarks
Recent and Sub- Delta fans of gravel and sand where foot-
Recent hills join the plains; more than 40 feet
locally.
Alluvium of the Mesopotamian plain
mostly silt; up to at least 130 feet.
Sand-dunes mainly as a strip in the south
to the west of the Shatt al Arab.
Sand and gravel forming the cover of
wadis in the west.
River terraces, chiefly gravel, very variable
and at varying heights; up to 200 feet thick
in the mountains and foothills.
Screes in some of the north-eastern lime
stone mountains.
Pliocene and Mio- Bakhtiari conglomerates consisting largely
• pliocene of limestone cobbles with interbedded
pebbly sandstones and lenticular bodies
of sandy silt. Partly made up of fossil
delta fans, partly outwash and adjoining
piedmont deposits. Thickness variable
0—3,500 feet, but apt to be exaggerated
♦ owing to depositional dips. Varies from
well cemented to poorly consolidated.
Confined to the north and east. Rare
mammalian remains.
Pebbly sandstones and gravels merge into
recent sands and gravels west of the
Euphrates and patches of chalk outwash
occur in certain structural basins.
Terra-cotta coloured clays and silts with
freshwater shells in local sunken basins
near the Arabian frontier. Freshwater
limestones are associated, e.g. Zahra
Limestone.
Upper Ears red-bedded, false-bedded
sandstones, silts and marls with rare limy
bands. Ripple marked. Up to 2,000 feet on
north-east. Seldom more than 100 feet
thick on the west of the Euphrates. Rare
chara. Marls often veined with fibrous
gypsum.
Middle and Red pebbly sandstone in the north-east.
Lower Miocene Lower Ears beds forming a complex se
quence of red, green, grey, and yellow
shale, marl, and silt interbedded with
several thin shelly limestones and a few
anhydrites in the lower part, passing up
into a series with little limestone but
more anhydrite and some beds of rock
salt and salty marl. Ostrea latimarginata
and Clausinella abundant at some points.
Up to 6,500 feet thick in the north-east,
though usually not more than 2,500 feet
on this flank. The whole series not much
more than 100 feet thick to the west and
south of the Euphrates.
Upper and
Middle Miocene
Water-yielding beds sup
plying important towns
Very fertile where irri
gated.
Evidence of late uplift
Very conspicuous in the
Middle Cretaceous
mountains.
Water-yielding beds of
importance.
Evidence of large uplift
and mountain building.
Recalling the deposits in
the down-faulted de
pressions of Turkey.
Shallow brackish and
freshwater conditions
accompanying a general
emergence.
Change of climate accom
panying change of con
ditions. Folded rocks
emerging on the north
east. Sea in the south
western depression con
centrated progressively.
Just overlapping the wes
tern platform.