Page 353 - Carbonate Facies in Geologic History

340 The Rise of Rudists; Middle Cretaceous Facies in Mexico and the Middle East

Table XI-2. Middle and Lower Cretaceous correlations in the Middle East

Cretaceous Arabia Arabia Iran
stage Iraq NO. Persian Gulf Qatar
. Mauddud 1st Mauddud Bangeslan
.: ';" .....,....---1-_
.
Albian Nahr
Umr
shale

Shuaiba 1st
Aptian
Howar shale
a.
:::>
0 Koraib 1st Upper
~
01 Borremian Khami
group
0
E
0 ----- IFohliyanl
E
0 Neocomian Yamaha
.c. grainstone
I-
Sulruy
mudstone Sulal'f lime
mudstone

The major positive element is the Arabian shield which stretches north into
Jordan and western Iraq. A northward projection, the Mosul block, remained
high during the Cretaceous and was enough protected from terrigenous influx to
act as a nucleus for a halo of carbonate platform sediments.
Two major troughs existed east of the Arabian shield. The northern one was a
part of the Zagros geosyncline and stretched from Turkey to the west central
Iranian coast. It is somewhat elongate. Its east side was sediment-starved, and
deep, from Jurassic until well into Cretaceous as indicated by a thin section of
dark, muddy, pelagic sediments, including radiolarites. The northern Arabian
shield furnished a considerable amount of coarse clastics. These poured into the
southwestern part of the geosynclinal trough which is generally termed the Bas-
rah basin; as much as 1Ooo m of mixed terrigenous and limestone sediment accu-
mulated here during Early and Middle Cretaceous. Quartz sands began to appear
from the Arabian source area in Iraq during the earliest Cretaceous and the
terrigenous influx progressed southward throughout the Cretaceous period. The
Albian-Cenomanian sands of the Wasia Formation are best developed at the
southern extremity of the Hasa coast at Bahrein Island. All of these sands,
Garagu (Lower Cretaceous of Iraq), Zubair-Byadh (Aptian-Barremian of Saudi
Arabia), and Wasia (Albian of Arabia) are alluvial to the west and have shoreline
facies in the subsurface beneath the present shoreline of the Persian Gulf. The
clays were washed eastward into the geosyncline where they form the dark shales
and silts of the Sarmord, Ratawi, Nahr Umr, and Kazhdumi, the obvious source
for much of the Middle East oil.