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The Basement
rocks
The Basement
rocks of Yemen represent the southern extension of the Arabian
Shield
Fig(2), is of
Paleoproterozoic to Neoproterozoic age. In Yemen has identified
five terranes, which can be correlated with the eastern margin of
the Arabian Shield in Saudi Arabia and with northern Somalia.
These include Pleoproterozoic to Neoproterozoic gneissic terranes
and Pan-African island arc terranes and suture zones. These are
the Afif, Abas and Mahfid terranes (gneiss terranes) and Al-Bayda’
and Mukalla terranes (arc terranes). The Basement of Yemen
provides the link between the arc collage of the Arabian Shield
and the gneissic Mozambique belt of east Africa.
In the Upper Neoproterozoic constitution of the shape of
the Arabian plate has commenced, so that in Yemen a transitional
stage between the basement and platform was development and
evidenced by the deposition of folded sediments of the Ghabar
Group (Infracambrian)
Fig(2),
Fig(3).
Similar subsurface Infracambrian deposits are known from Qinab-1
well (southern flank of the Rub’ Al-Khali basin)
Fig(4), which are defined
formally as Qinab Group
Fig(2).
Infracambrian succession
Fig(3)
is
represents by the Ghabar Group
Fig(2), which developed only between Wadi Ghabar and
Wadi Minhamir areas. The Ghabar Group (InfraCambrian/ ?earliest
Paleozoic)
Fig(2) is
formally divided into four formations (Minhamir, Shabb, Khablah,
and Harut Formations). It consists of different sediments
(conglomerate, siltstone, sandstones, shales, carbonates) of very
low metamorphic degree and rest unconformably on the igneous
extrusive Tha’lab Group of Neoproterozoic age and overlain
unconformably and with angularity by the Qishn Formation of Early
Cretaceous age.
The Paleozoic sediments
Fig(3)
The Paleozoic
sediments deposit after the accretion Afro-Arabian Plate from
parts of the Gondwanan continent. Continental sedimentation and
deposition of sandstones, which represent by the Wajid Formation
(Cambrian/Carboniferous) and glacial deposits of tillites, shales
and drop stones of the Akbarah Formation (Upper
Carboniferous/Permian) in the NW of Yemen. Subsurface sections are
distributed in the San’a basin as well as in the Sab’atayn basin (Marib
sector)
Fig(4) by
probably thick sequence of the Wajid and ‘Akbarah Formations,
whereas in the northern part of Tihamah basin
Fig(4), only deposit of the
‘Akbarah Formation was observed.
The Rub’ Al-Khali
basin
Fig(4) (southern
flank) constitutes thick subsurface sedimentary strata of
Paleozoic age, and composed of thick clastics and marine sediments
represent by the sandstone of the Dibsiyah Formation
(Cambrian/Lower Ordovician), the Qalibah Formation, mainly the
Qusaiba Member (Lower/Middle Silurian), which represents the
excellent source rocks of the Paleozoic deposits; the Khussayyan
Formation (Upper Devonian/Lower Carboniferous), which consists of
sandstone and the Juwail Formation (Middle Carboniferous/Lower
Permian), which consists mainly of sandstone.
The Mesozoic sediments
The Mesozoic sediments started after the regional emergence
representing by the Jurassic and Cretaceous successions. Triassic
sediments of Falanj Formation crop out only in the south eastern
part of the
Suqatra Island.
Triassic successions of the Sudair Formation only distributed in
the subsurface sections in the Rub’ Al-Khali basin
Fig(4) (southern flank)
that composed of green and red shales.
The Jurassic succession started with continental sediments in the lower part
of the Kuhlan Formation on the peneplained basement and on
Paleozoic in NW Yemen. First marine sediments deposit of shale and
sandy carbonates in the upper part of the Kuhlan Formation, which
continued by major transgression with platform development and
shallow marine deposits of Shuqra Formation. The upper part of the
Shuqra Formation in the subsurface section of the Sab’atayn basin
Fig(4) (Marib sector) is
formally defined as Arwa Member and composed of deep marine
carbonate deposition that can give an evidence of early rifting in
the Marib sector.
Initial Rifting in the
Lower
Kimmeridgian time with the deposition of deep marine sediments in
all Mesozoic rift basins, mainly the Siham-Ad-Dali’, the Sab’atayn
and the Say’un-Masila basins
Fig(4). Continued rifting and coincident sea level rise
followed by deposit of deep marine sediments (Lower and Upper Madbi Shales Members), well bedded limestone (Ma’abir Member) and
turbidites (Rafad Member) in the margins of the Sab’atayn and
Say’un-Masilah basins
Fig(4).
Isolation of the Sab’atayn basin
Fig(4) gives rise to deposition of thick halite (Shabwah
Member), bituminous shale (Layadim Member), and gypsum and
turbidites (‘Ayad and Maqah Members) of the Sab’atayn Formation.
Continuous transgression laid down to deposition of shallow and
deep marine sediments of the Nayfa Formation (Upper Tithonian/Lower
Berriasian). Subsurface succession of the Madbi Formation in the
Sab’atayn basin (Marib sector)
Fig(4) represented by the following members, the Meem,
Lam, Haniyah, Harib, ‘Ayban and Raydan Members. The Sab’atayn
Formation in the Sab’atayn basin (Marib sector)
Fig(4) divided into Yah,
Seen, Alif and Safir Members. The sediment succession from Shuqra
to Nayfa Formations is formally named as ‘Amran Group.
Continuous transgression into the Cretaceous succession
in the east and deposit of deep and shallow marine sediments of
the Sa’ar Formation (Samarmar and Qalana Members) as well as
districted clastics, deltaic development (Ghayl Member) in the
upper part of the Sa’ar Formation. The age of the Sa’ar Formation
is Middle Berriasian/Lower Valanginian.
After the global sea level fall representing by continental
sediments followed by marine transgression in the Hauterivian/Barremian
time, which maximum flooding surface reaching the Al-Mahfid uplift
and gradual regression representing the Qishn Formation as post
rift fill with deposition of open marine carbonates in the east,
fluvial deltaic and marine input in the west (Qishn Clastics and
Qishn Carbonates Members) followed by sea level fall. In the
subsurface section (Al-Furt-1 well) of the Jiza’-Qamar basin (Jiza’
sector)
Fig(4) a major
subsidence during Hauterivian/Early Barremian times took place and
deposition of Sa’af Member, which consists of shale and marl
sediments with minor limestone interbeds.
Two major transgressions during the Middle Albian and
Cenomanian give rise for interfingering of fluvial, deltaic and
marine deposition of the Harshiyat and Fartaq Formations.
Dominantly fluvial, deltaic deposition of the Mukalla Formation (Turonian/Campanian)
with marine input in the west deposit of Lusb Member (Turonian?/Santonian)
and continuous more marine influence in the east, specially in the
Jiza’-Qamar basin
Fig(4) with the deposition of marine sediments of Dabut Formation
(Early Campanian/Early Maastrichtian), which represents the upper
part of Mukalla Formation in the subsurface section. The
Cretaceous ended by the Maastrichtian transgression and the
deposition of limestone and marl of the Sharwayn Formation.
Generally, the Cretaceous succession is characterized by
continental sediments in the west that formally named Tawilah
Group (undifferentiated)
Fig(3),
by interfingering of continental and marine sediments in the
centre represented by the Tawilah Group
Fig(3) that divided into
Qishn, Harshiyat, and Mukalla Formations, and marine sediments in
the east represented by the Mahra Group, which include
Qishn, Fartaq, Mukalla, Dabut, and Sharwayn Formations.
The Cenozoic sediments
The Cenozoic sediments is developed as Paleogene and
Neogene Sediments and represented by the Hadramawt Group
(Upper Paleocene/Middle Eocene)
Fig(2), the Shihr Group (Lower
Oligocene/Pliocene)
Fig(2)
and the Tihamah Group (Upper Oligocene/Pleistocene)
Fig(2). The Hadramawt
Group
Fig(2) deposited in the Paleogene time after the regional major
transgression in the Upper Paleocene time and continued to the
Lower Eocene with the maximum flooding surface reaching Al-Mahfid
Uplift and represented by the Umm er Radhuma Formation (Shammar
Member at the base and Jawl Member at the top) and Jiza’
Formation. Within the deposition of the Hadramawt Group
Fig(2) regression happened
during the Lower Eocene and marked by the sabkha deposit of the
Rus Formation. This was followed by the Middle Eocene major
transgression, which reached Al-Mahfid Uplift give rise to deposit
of the Transitional Beds Member but with continuous gradual
regression to the east laid down a lateral facies changes of the
equivalent formations (the Mayfa’ah, the Kaninah and the Habshiyah
Formations) before the regional Middle Eocene unconformity caused
by the regional uplift of much of Arabia between the uppermost
Middle Eocene and Lower Oligocene.
The riftoginous major deposition related to the Gulf of
Aden and the Red Sea rifting and represented by the thick
sediments of the Shihr and Tihamah Groups
Fig(2).
The Shihr
Group (Oligocene/Pliocene)
Fig(2) is formed by the syn- and post-rift sedimentary
successions along the Gulf of Aden Yemeni side including the
Libakhah, Ambakhah and Buwaysh Formations (Oligocene), the Fuwwah
Formation (Lower/Middle Miocene), and the Irqah Formation (Upper
Miocene/Pliocene). Subsurface offshore deposits mainly in the
MUKALLA-SAYHUT basin
Fig(4) include the Ghaydah Formation (Oligocene/Lower Miocene), Hami
Formation (Lower/Middle Miocene), and the Sarar Formation (Upper
Miocene/Recent). The Taqah Formation is developed in Jiza’-Qamar
basin
Fig(4) as
equivalent of Ghaydah and Hami Formations (As-Saruri and Beydoun,
1998 and As-Saruri, 1999).
Accordingly, in
the Gulf of Aden marine incrusions into coastal embayment gave
rise to heterogeneous deposits of the Shihr Group
Fig(2) of
Oligocene-Pliocene age; offshore, in the subsiding sectors of the
rift, thick clastics were being poured in, which were of turbidite
nature. Onshore, the Shihr Group
Fig(2) deposits reflect disconnected basin
Fig(4) deposition and
facies are provenance and environment-dependant, whereas offshore,
more uniform clastic deposition with occasional shoal carbonates
prevail (As-Saruri & Langbein, 1996; As-Saruri and Beydoun, 1998).
Initially, marginal marine to restricted evaporitic deposition
characterized the Lower Oligocene deposits, to be followed in the
Middle Oligocene by major depending and rapid syn-rift marine
clastics depositions (Hughes et al., 1991).
The Tihamah
Group (Upper Oligocene/recent)
Fig(2) represents the syn- and post-rift sediments in
the Tihamah basin
Fig(4)
on- and offshore of the Red Sea along the Yemeni coast and
includes the Zaydiyah Formation (Lower Miocene), Maqna Formation
(Lower/Middle Miocene), Salif Formation (Middle/Upper Miocene) and
Abbas Formation (Pliocene/Pleistocene), which represent the top
unit of the Tihamah Group (As-Saruri, 1999; and As-Saruri and
Beydoun, 1998).
However, the
development of the Red Sea- Gulf of Aden rifts in Oligocene/Recent
time, which resulted in massive uplift along the rift boundaries,
where huge bimodal volcanic rocks and their associated Neogene
intrusions (granite, syenite, diorite, gabbro) formed the high
plateau of the western Yemen province.
The
Yemen Volcanic Group
Fig(2)
Includes all the
Cenozoic volcanic rocks, which is divided into the Yemen Trap
Series (31.6 - 15 Ma) that consists of thick series of mainly
flood volcanic rocks and Yemen Volcanic Series (10 - 0 Ma) that
represents thinner series of mainly peralkaline intraplate
basaltic volcanic rocks (Mattash and Balog, 1994). The Yemen
Volcanic Series is divided into older volcanic rocks intruded west
of Aden (10 - 5 Ma) and younger volcanic rocks east of
Aden
(5 - 0 Ma).
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