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The Republic of Yemen is covered by rocks
ranging in age from Precambrian to quaternary.
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Basement Rocks
The Precambrian basement rocks in
Yemen comprise metavolcanic, metasedimentary,
gne iss
and migmatite belts
produced in arc environments intruded by
post tectonic granites and granodiorites. These
are found throughout western Yemen from the
northwest (Sa’dah - Al Jawf) and southwest areas
(Marib-Al-Bayda), in addition to small outcrops
in south of Taiz and west of Mukalla. The
oldest known rocks in Yemen occur in the Al
Bayda terrane which contains late Archaean aged
(Sm-Nd: 2700-2900 Ma) gneisses, amphibolite
dykes and granites
Sedimentary Rocks
These
comprise the following:
Paleozoic
Sediments
• Ghabar Group (Infra–Cambrian-Earliest
Paleozoic):Sandstone, limestone, silt, gypsum.
• Qinab Group (Infra Cambrian-Lowest Cambrian):
Volcano–sedimentary succession consisting of
dolerite, sandstone, silty shale and tuff.
• Wajid Formation (Cambrian - Carboniferous):
Quartz sandstone.
• Akbarah formation (Late
Carboniferous-Permian): Tillite (pebbles &
boulders of basement rocks), shales,
mudstones, sandstones and siltstones.
Mesozoic Sediments
•
Kuhlan Formation (Lower–Middle Jurassic):
Sandstones, thin claystone and siltstone
interbeds.
• Amran Group (Middle Jurassic-Lower
Cretaceous): Carbonate marl/shale with
evaporitic succession.
• Tawilah Group (Cretaceous): Sandstone with
siltstone, marl, and shale, often interbedded
with sandstone and also forming distinct marl or
shale intervals and with generally persistent
limestone-marl clasts.
• Mahra Group (Cretaceous): Limestone, marl, and
shale, often interbedded with sandstone.
Cenozoic Sediments
•Hadramawt Group (Paleocene-Middle Eocene):
Dolomite, shale, limestone with chalk and
dolomite, marl, papery shale, bedded gypsum,
and alternating sand stone and claystone.
• Majzir Formation (Paleocene-Lower Eocene):
A shallow marine-littoral sandstone
succession. 
•Shihr Group
(Oligocene-Pliocene): Conglomerate,
sandstone, silt, lime tone and gypsumÒ
• Tihamah Group (Middle-Upper Miocene):
Sandstone, conglomerate, gypsum, rock
salt, shell, mudstone and limestone.
Volcanic
and Intrusive Rocks
The
was a time of Regional uplift occurred in
western Yemen in the Paleocene/Eocene as
evidenced by intermittent volcanic activity
commencing in the Early Eocene which
culminated in Oligocene–Miocene times with
extensive extrusive and plateau flood basalt
eruptions forming the Yemen Volcanic Group.
This comprises an older “trap” series and
younger Volcanic Series.
These series include the whole spectrum of
basaltic lithologies to silicic ignimbrites
and tuffs. Sedimentary units, generally
occurring as lenses of limited extent and
thickness, occur in many parts of the
volcanic sequence between flows (Geukens,
1960, 1966). These are generally composed of
lacustrine deposits consisting of calcareous
sandstone, mudstone and reworked volcanic
clasts. Also observed in inter-trap
sedimentary units are fluvio-aeolian sands
and palaeo-soils, generally lateritic, often
developing along plane surfaces but at times
locally cutting across different beds.
The Yemen Volcanic Group is intruded by
granitoid rocks along much of the edge of
the High Plateau of Yemen, which forms the
great eastern escarpment of the Red Sea.
Intrusions also occur in the Sana’a
and Taiz districts.
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