'File 35/5 Development of Grazing Grounds (Supplies from Persia)' [‎22r] (43/118)

and m the oorglna of the exposed area oonoist of Hzoastono^ ToerXa
and shales. The marls and shales provide structural traps for the
accumulation of rain watar trm small catchment areas within the Hia
hook and are the source of supply of water to the hand* dug wells which
exist near the Kim Rock in the exposed area. (Bofa* Hanainl, Hafir**
Bakhir, 3ofra etc. )• In the center of the exposed area (including the
limits cf the oil producing area)* the formations are the predominantly
limestone beds which constitute the source beds of -fetor Zone ”0” water ,
Rawing ffo. 2RS-5780-Q attached gives structural contours on
the top of the Brown Crystalline Limestone (ftater Zone ”B*) and it will
be observed that what may be termed a structural "terrace* extends around
the northern end of the Island and down the flanks of the structural to
at least as far as Zellak on the west and to 31tra on the east. This
"terrace" has evidently been caused by slumping in the Chalky Zone by the
removal of anhydrite and/or gypsum, either by solution* or what is more
likely* the action of sulphate reducing bacteria# On the crest of the
structure* and for some distance dawn dip* there is no anhydrite remain*
lng in the Chalky Zone but as one goes further down dip, particularly on
the northern plunge* considerable aggregate thickness of anhydrite is
developed. This slurping phenomenon is undoubtedly responsible for the
vary obvious* but purely superficial, anticlinal fold near Burl.
structure at depth Is less oomplax but as this does not enter
into the present problem it will not be discussed further#
smmmMjsm
/*♦*
The domestic water of Bahrein ie obtained from the following
sonesi-
1. Shallow (3urfBoe) ««tar amw
This none supplies most of the shallow hand-dug wells in the
north-oast am port of the Island* and le not to be confused with Water
Zones "A** "3* and *0" where these occur near the surface in ether
localities. It consists of a perched water body# occurring in loose
uartosnnry sediments which rest on inpcrtiotts shale at a depth below
sefe-levwl. The water if derived xmnly from the deeper aquifers (Mew
Zones "A” and "8") by seepage from springs* leaking artesian wells* ana
by the infiltration of ivriirtien water derived from these —arses | a
mall proportion is also derived from local rainfalls. A static head of
aero plus is maintained by the sea to which these sediments ere exposed.
hsprisened between a rising structure on the landward side end
a sea-water heed on the sea-word side* there is little eireulatiea in
this sons other then that caused by overflow along the coast and by with
drawal from open wells. This fact* ccmbinsd with the pdatl*/* pmmi by