lecture note 2 phanerozoic historical geology of arabian peninsula

Lecture- 11Phanerozoic Historical Geology of Arabian Peninsula

Saudi Arabia sits in the middle of the Arabian tectonic plate, which stretches from the Gulf of Aden and Arabian Sea to southeastern Turkey, and from the Red Sea to the Zagros Mountain front in Iran

Divergent boundaries are evident to the west and south in the geologically recent spreading centers of the Red Sea and Gulf of Aden. The still-active convergent margin lies to north in Turkey and to the east in Iran. A continental strike-slip fault zone bounds the plate in the northwest, where the Dead Sea Transform goes from the Gulf of Aqaba through the Dead Sea and Syria into southern Turkey. A second transform boundary exists to the southeast, offshore Oman, in the intra-oceanic Owen Fracture Zone.

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Crustal Structure

The Arabian Plate consists primarily of thick continental basement, which outcrops prominently on the Arabian Shield.

A composite traverse of the Arabian plate from the Red Sea, across the Arabian Shield and eastern sedimentary basins, to the Arabian Gulf and the Zagros Mountains.. Oceanic (basaltic) crust in the central Red Sea shows up as very thin at around 5-6 km, while the Arabian Precambrian shield is relatively thick at 45 km. The crust is very thick (50-60 km) beneath the Zagros Thrust Zone, a result of the Arabian crust being partially underthrust beneath Asia since mid-Tertiary times

A striking feature of sedimentation in the Arabian Platform is the very extensive lateral persistence of many formations over distances of up to several thousand kilometres.

Many unconformities, or disconformities, occur within the stratigraphic succession of the Arabian Platform areas. One of the most pronounced of these is the sub-Unayzah (or sub-Haushi) unconformity (Powers et alii 1966; Al-Laboun 1988), which is of regional extent, affecting not only the Arabian Platform but also the Mobile Belt of northeast Iraq and southern Iran.

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Sedimentary Cover

The Phanerozoic sedimentary in the Arabian Plate began with the deposition of calstic rocks and later carbonates and evaporates in the above mentioned grabens or pull-apart basins (in Oman and eastern Arabia). The formation of salt basins (Infracambrain-Cambrian) in the eastern part of the Arabian plate together with local structures and basement horst blocks make an excellent condition for oil traps Early Paleozoic:Central Arabia was a stable subsiding passive margin flanking Gondwanaland.Shallow-marine, fluvial, sandstone, siltstone, and shale were deposited on low-relief erosion surface formed on the Precambrian basement Late Ordovician-Early Silurian:The depositional cycle interrupted by polar glaciations. Arabia at this time was within 30 of the south pole. Sea level rise and fall caused regression and transgression of the ocean floor a round Gondwanaland

Phanerozoic Historical Geology of Arabian Peninsula

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Middle – Late Paleozoic Geologic History Hercynian Orogeny structural event initiated the uplift of central Arabian and tilted the Arabian plate eastward, exposing Devonian and older rocks to erosion and transforming the northeast Gondwana margin from a passive to an active margin

Devonian:The passive margin of Gondwanaland in Arabia became active because of the Hercynian orogenic activity

The regional uplifting during Devonian is reflected in the development of the Central Arabian arch, where the Devonian sedimentary rocks are absent.

This resulting in the initiation of structures that eventually controlled the location of Paleozoic-hosted oil fields in central Arabia.

Late Carboniferous: Unayzah formation calstic rocks, which constitute major oil reservoirs where they overlie appropriate Hercynian structures, mark the resumption of sedimentation in the Late Carboniferous.

Permian: Deposition of the Khuff formation which represents the earliest major carbonate unit in Arabia, followed, concurrent with rifting and Gondwana breakup in the Zagros region.

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Middle – Late Paleozoic Geologic History

Plaleolatitude positions of Arabian plate during Paleozoic.

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Mesozoic Geologic History :

-The Mesozoic geologic history of the Arabian plate is marked by the formation of structural highs and lows.- In central Arabia, regional extension caused by continued breakup of Gondwana and rifting along the Zagros belt resulted in the Triassic reactivation of Hercynian structures and syn-sedimentary thinning of Triassic deposits over growth faults.- Reactivated basement structures, present in Saudi Arabia in the form of Mesozoic anticlinal highs trending N-S. These highs affected the younger sedimentation, particularly during the Upper Cretaceous causing anticlinal drape folds and helping to create the Mesozoic oil fields of Saudi Arabia-The reservoir rocks are Jurassic and Cretaceous, into which Jurassic hydrocarbons migrated during the Tertiary.

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Middle Jurassic and Early CretaceousThe axial region of central Arabian arch underwent inversion

and became a basin. Late Cretaceous:The arch reformed again as a result of uplift in southern

Arabia and continued subsidence to north.Middle Cretaceous:

Concurrent with the opening of the Atlantic, Neo-Tethys closed and the African-Arabian and Eurasian plates converged.

Mesozoic Geologic History

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Mesozoic Geologic History

Mesozoic-Cenozoic Tectonostratigraphic events and Sea-Level Fluctuation of Arabian And Africa Plates

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Arabia began colliding with Asia along the Zagros tectonic front in the mid-Tertiary. An extensive foreland basin formed as the edge of the Arabian Plate was depressed beneath the Zagros thrust, a feature that survives today as the Arabian Gulf. This compressional event produced another episode of structural growth on pre-existing structures, completing formation of the Arabian oil fields.

Shortly after the collision with Asia began, extension was initiated in the Red Sea and the Gulf of Aden. Rifting was very slow at first, and indeed is thought to have ceased as the collision with Asia restricted the plate's northward motion. It was renewed, however, about 10 million years ago when central and southeastern Turkey began to move westward and consequently Arabia move northwards, and sea-floor spreading and basaltic crust generation began in the Red Sea.

The Sinai Peninsula, which initially moved with the Arabian Plate, was left behind with Africa as the Dead Sea Transform became more active about 5 million years ago. About 100 km of northward displacement of the Arabian Plate has occurred along the Dead Sea Transform since that time.


Cenozoic Geologic History

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Cenozoic Tectonic events in Arabian Plate.

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Lithological Characteristics of the

Phanerozoic Eon Characteristics of the Early Paleozoic lithological

units•Early Plaeozoiz in general is a transgressive phase depositing

mainly clastic, carbonates and marls depending on the depth of the sea.

•It was a phase of periodic instability leading to alternating shallow and deep-water facies.

•This instability culminated in a Late Ordovician early Silurian glaciations. (coming from north Africa)

•It also culminated in a post (Late) Silurian tectonic episode that separated the Early Paleozoic from the Late Paleozoic rocks by major break .

•The alternation of deep and shallow water facies has provided excellent opportunities for both hydrocarbon and ground water accumulations.

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Characteristics of the Late Paleozoic lithological units

•It was generally a phase of marine regression except for the Late Permian which extensive phase of marine transgression.

•A very pronounced glacial phase affected the whole region (as part of the Southern Hemisphere) during late Carboniferous-early Permian time.

•This glacial phase was coming from the south- southwest and it did not exceed the southern 1/3 of the Arabian plate.

•Most of the rock units representing this span of time in the Middle East is dominated by clastic deposits (sandstone, siltstone, shales, tills, and tillites .. etc) mostly of continental origin(either eolion, fresh water or glacial) with minor intercalating tongues and lagoonal, littoral or even shallow marine origin at the peripheries of the Arabian plate.

•Such condition have made the Late Paleozoic sequence in the Middle east an ideal sequence for hydrocarbon accumulation, coal deposits, ground water storages, clay deposits accumulation and many other economical values. (For example, oil and gas reserves in Unayzah Formation)

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Map of Paleozoic petroleum systems, showing location of the various reservoirs and the two main source rocks (Silurian and Precambrian).

Lithological Characteristics of the

Phanerozoic Eon Characteristics of the Cenozoic lithological units

During the Paleocene and early Eocene, much of the eastern part of Arabian Plate was a wide, shallow carbonate and evaporitic platform in response to withdrawal to the south of the Neo-Tethys sea.

Rocks of Paleocene-Eocene age are generally calcareous with typical shallow-water lithologies.

The Early Eocene witnessed the introduction of persistent and widespread evaporite precipitation. Anhydrite in considerable thickness was deposited in the Rub al Khali basin.

Eastern Arabia underwent uplift and subaerial erosion from the Oligocene into the Miocene. The Oligocene through Pliocene (Neogene) of Saudi Arabia is composed of four formations and totaling about 350 m in thickness.

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Characteristics of the Cenozoic lithological units

In middle Miocene time minor intermittent flooding. The Miocene sequence in Arabia probably represents in effect a thin wedge of lacustrine, fluvial, and coastal plain deposits peripheral to the main area of subsidence in Iran, and Iraq where evaporite-forming conditions prevailed.

The Oligocene through Pliocene (Neogene) sedimentary section of Saudi Arabia is composed of, in ascending order the Hadrukh, Dam, Hofuf, and Kharj Formations.

The early Miocene Hadrukh is mostly nonmarine sandy limestone and calcareous sandstone and is conformably overlain by marls, limestone, and claystones of the middle Miocene Dam Formation.

The late Miocene–early Pliocene Hofuf Formation consists of marls, sandy limestones, conglomerates, and argillaceous sandstones of continental origin.

The overlying Pliocene Kharj Formation consists of irregular-bedded limestone, sand, and gravel conglomerates, with some sediments indicating deposition in a freshwater, lacustrine environment

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Characteristics of the Cenozoic lithological units

Dammam Formation accommodates the Khobar and Alat acquifers (Al-Khobar is extensively used in Al-Qatif, Al-Khobar, Dhahran, and Al-Hasa). Alat is used in RasTanura, and An Nuayriyah.

Houfuf Formation characterizes by great Arial extent over which gravel deposits of this unit and interior equivalent are found. Probably at the end of Dam there was a general tilting of the Arabian foreland and a rapid erosion which furnished the gravel incorporated in the Hofouf.

Tertiary Intrusions Dike system extends through the western part of the Arabian

Shield from the Yemen border to the Gulf Aqaba. They are gabbro, diorite, and hypabyssal intrusive rocks. The age of these rocks range between 19-27 m.y. They reach 300 m in width and tend to branch and anastomose. Some can be traced to several kilometers. They are coarse grained in the middle and chilled and fined at the edges.

These dikes give rise to north-northwest trending aeromagnetic lineaments.

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SEDIMENTARY SECTION OF SAUDI ARABIA

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The sedimentary section of Saudi Arabia exposed above the Precambrian and falls into eight major divisions:

1- Cambrian through Carboniferous

Saq, Al-Qassim, Sarah, Al-Qalibah, Al-Tawaeel, Al-Jouf, Al-Jobah, and UnizahDominantly coarse clastic rocks with some thin carbonate beds in the uppermost part.

2- Upper Permian through Upper Triassic

Khuf, Sudair, Al-Jilh, and Manjour

Alternating non marine-marine units, dominantly clastic but with thick calcareous sections at the base and in the middle

3- Lower and Middle JurassicMarrat, Dhruma, and Twaiq Mountain In central Arabia marine shale interbeded with carbonate grades to sandstone in the northern and southern parts4- Upper Jurassic and early Lower CretaceousHanifah, Jubailah, Arab, Hith, Sulaiy, and YamamahMostly carbonate but with alternating evaporate normal marine cyclic deposits near end of Jurassic5- Late Lower Cretaceous

Buwaib and BiyadhDominantly coarse clastic rocks with thin basal Carbonate

unit 6- Middle Cretaceous

Wasia (in the north Skaka) Dominantly coarse clastic rocks


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7- Upper Cretaceous to EoceneAruma, Umm er Radhumah, Rus, and DammamCarbonate units but in subsurface lower Eocene includes evaporite section.8- Miocene and PlioceneHadrukh, Al-Dam, Al-Hofuf, and Al-KharjClastic rocks dominantly sandy limestone and sandstone


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The sedimentary section of Saudi Arabia exposed above the Precambrian and falls into eight major divisions:

1- Cambrian through Carboniferous

Saq, Al-Qassim, Sarah, Al-Qalibah, Al-Tawaeel, Al-Jouf, Al-Jobah, and Unayzah

Dominantly coarse clastic rocks with some thin carbonate beds in the uppermost part. 2- Upper Permian through Upper Triassic

Khuf, Sudair, Al-Jilh, and Manjour

Alternating non marine-marine units, dominantly clastic but with thick calcareous sections at the base and in the middle

3- Lower and Middle Jurassic

Marrat, Dhruma, and Twaiq Mountain

In central Arabia marine shale interbeded with carbonate grades to sandstone in the northern and southern parts.

4- Upper Jurassic and early Lower Cretaceous

Hanifah, Jubailah, Arab, Hith, Sulaiy, and Yamamah

Mostly carbonate but with alternating evaporate normal marine cyclic deposits near end of Jurassic

5- Late Lower Cretaceous

Buwaib and Biyadh

Dominantly coarse clastic rocks with thin basal Carbonate unit


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6- Middle Cretaceous

Wasia (in the north Skaka)

Dominantly coarse clastic rocks

7- Upper Cretaceous to Eocene

Aruma, Umm er Radhumah, Rus, and Dammam

Carbonate units but in subsurface lower Eocene includes evaporite section.

8- Miocene and Pliocene

Hadrukh, Al-Dam, Al-Hofuf, and Al-Kharj

Clastic rocks dominantly sandy limestone and sandstone

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(Edgell, 1992)

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lecture note 2 phanerozoic historical geology of arabian peninsula

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