Arabian-Nubian Shield
Encyclopedia
The Arabian-Nubian Shield (ANS) is an exposure of Precambrian
crystalline rocks on the flanks of the Red Sea
. The crystalline rocks are mostly Neoproterozoic
in age. Geographically - and from north to south - the ANS includes the nations of Israel
, Jordan
. Egypt
, Saudi Arabia
, Sudan
, Eritrea
, Ethiopia
, Yemen
, and Somalia
. The ANS in the north is exposed as part of the Sahara Desert and Arabian Desert
, and in the south in the Ethiopian Highlands
, Asir province of Arabia and Yemen Highlands.
The ANS was the site of some of man's earliest geologic efforts, principally by the Egyptians
to extract gold
from the rocks of Egypt and NE Sudan. This was the most easily worked of all metals and does not tarnish. All of the gold deposits in Egypt and northern Sudan were found and exploited by Egyptians, but new gold discoveries have been found in Sudan, Eritrea, and Saudi Arabia. Pharonic Egyptians also quarried granite
near Aswan
and floated this down the Nile to be used as facing for the pyramids
. The earliest preserved geologic map
was made in 1150 BCE to show the location of gold deposits in Eastern Egypt; it is known as the Turin papyrus
. The Greek name for Aswan, Syene; is the type locality for the igneous rock
syenite
. The Romans followed this tradition and had many quarries especially in the northern part of the Eastern Desert of Egypt where porphyry
and granite
were mined and shaped for shipment. Precious and industrial metals, including gold, silver, copper, zinc, tin, and lead, have been mined in Saudi Arabia for at least 5,000 years. The most productive mine in Saudi Arabia, Mahd adh Dhahab
("Cradle of Gold"), has been periodically exploited for its mineral wealth for hundreds or even thousands of years and is reputed to be the original source of King Solomon's gold. Today, mining at Mahd adh Dhahab is conducted by the Saudi Arabian Mining Company, Ma'aden.
that underlies NE Africa, SW Asia, and Arabia. Geophysical
studies inform us that ANS crust is about 40–45 km thick, typical for continental crust elsewhere. Geologists are interested to study this crust because it provides an outstanding opportunity to learn how continental crust forms. Elsewhere in Arabia and NE Africa the crust is buried beneath kilometers of younger, Phanerozoic
sediments and can only be reached by scientific drilling
.
Glaciers scoured this land during one of the Neoproterozoic Snowball earth
episodes (~630 Ma) and the remarkable Arabian-Nubian peneplain
is overlain by the greatest sand sheet on Earth, the Cambro-Ordovician Siq/Saq sands. This is exposed in spectacular cliffs like the site of Petra
in Jordan. The Arabian sandstones are overlain by thick deposits of younger sediments that dip and thicken eastwards into the Persian Gulf
. These sands are missing in most of Egypt and Sudan, instead the ANS is overlain by the late Mesozoic Nubian sandstones. All of these sediments were peeled off by erosion to expose the ANS, and much of this sand was reworked by desert winds to make great sand dunes in western Egypt and the Ar Rub al Khali (Empty Quarter
) of Arabia.
The embryonic ocean called the Red Sea
has slowly widened by rifting over the past 25 million years. Rifting typically causes uplift of its margins, or 'rift shoulders', and the covering sediments were removed by erosion as the Red Sea widened, allowing us to examine the basement geology of this region. This examination is favored also by the desert climate of the region - there is no soil, little vegetation, and few cities or roads to obscure the geology.
Gondwana
. The most intense part of the collision occurred in what is today southern Africa, where older crust in Tanzania
. Mozambique
, and Madagascar
was remobilized to form the Mozambique Belt. This great collision was responsible for the Pan-African orogeny
near the end of Neoproterozoic time. The crust of the Mozambique Belt is quite different from that of the Arabian-Nubian Shield, which is predominantly 'juvenile' crust, that is, crust that formed from partial melting of Earth's mantle, although much older Archean
and Paleoproterozoic
crustal materials is exposed west of the Nile in Egypt, in the SE part of the shield in Arabia, in eastern Ethiopia, and in Yemen.
The ANS took about 300 million years to form. The oldest rocks associated with the formative cycle of the ANS crust formed by coalescence of Island arc
s and back-arc basins
and perhaps oceanic plateaus. The oldest rocks associated with this cycle are about 870 million years old and are found in eastern Sudan and SE Arabia. Some of the oldest rocks are ophiolites
, which testify that formation of ANS continental crust
began with formation of oceanic crust
by seafloor spreading
, followed by the development of subduction zones and Island arc
s. The various island arcs collided and these tectonic terranes
sutured together during the time period 780 to 620 Ma to form an increasingly broad and thick nucleus of juvenile continental crust. This thickening resulted in the formation of several suture zones
, marked by obduction
of ophiolites and intense deformation. Crustal thickening was also accompanied by melting and magmatic fractionation of mafic magmas that ponded deep in the crust. These melts rose upwards to be emplaced as granitic plutons
. Magmatism during this episode is characterized by tholeiite
s and calc-alkaline
suites.
The welt of juvenile ANS crust was trapped between great tracts of converging continental crust. A protracted episode of continental collision
started at about 610 Ma ago and continued for about 50 million years. Collision was more intense in the south, in the Mozambique Belt, but it also strongly affected the ANS. N-S oriented upright folds and shear zones deformed the arc terranes and sutures in the southern ANS, forming elongate structures such as the Hamisana Shear Zone in NE Sudan. Farther north and east, the ANS was affected by the formation of the great NW-SE trending Najd system of strike-slip faults. The composition of igneous rocks became distinctively more evolved as the collision continued and the crust continued to thicken. Deep erosion, possibly by a continental ice sheet, happened during this time. All tectonic and magmatic activity ended by the time the Cambrian sandstones were deposited, about 530 million years ago.
A number of features have been ascribed to late stage extensional tectonics
including a widespread NE-SW trending dyke
swarm, NE-SW trending normal faults and NW-SE trending sedimentary basins filled with post-orogenic molasse
deposits
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
crystalline rocks on the flanks of the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
. The crystalline rocks are mostly Neoproterozoic
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
in age. Geographically - and from north to south - the ANS includes the nations of Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
, Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...
. Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, Saudi Arabia
Saudi Arabia
The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
, Sudan
Sudan
Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...
, Eritrea
Eritrea
Eritrea , officially the State of Eritrea, is a country in the Horn of Africa. Eritrea derives it's name from the Greek word Erethria, meaning 'red land'. The capital is Asmara. It is bordered by Sudan in the west, Ethiopia in the south, and Djibouti in the southeast...
, Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
, Yemen
Yemen
The Republic of Yemen , commonly known as Yemen , is a country located in the Middle East, occupying the southwestern to southern end of the Arabian Peninsula. It is bordered by Saudi Arabia to the north, the Red Sea to the west, and Oman to the east....
, and Somalia
Somalia
Somalia , officially the Somali Republic and formerly known as the Somali Democratic Republic under Socialist rule, is a country located in the Horn of Africa. Since the outbreak of the Somali Civil War in 1991 there has been no central government control over most of the country's territory...
. The ANS in the north is exposed as part of the Sahara Desert and Arabian Desert
Arabian Desert
The Arabian Desert is a vast desert wilderness stretching from Yemen to the Persian Gulf and Oman to Jordan and Iraq. It occupies most of the Arabian Peninsula, with an area of...
, and in the south in the Ethiopian Highlands
Ethiopian Highlands
The Ethiopian Highlands are a rugged mass of mountains in Ethiopia, Eritrea , and northern Somalia in the Horn of Africa...
, Asir province of Arabia and Yemen Highlands.
Egyptians
Egyptians are nation an ethnic group made up of Mediterranean North Africans, the indigenous people of Egypt.Egyptian identity is closely tied to geography. The population of Egypt is concentrated in the lower Nile Valley, the small strip of cultivable land stretching from the First Cataract to...
to extract gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
from the rocks of Egypt and NE Sudan. This was the most easily worked of all metals and does not tarnish. All of the gold deposits in Egypt and northern Sudan were found and exploited by Egyptians, but new gold discoveries have been found in Sudan, Eritrea, and Saudi Arabia. Pharonic Egyptians also quarried granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
near Aswan
Aswan
Aswan , formerly spelled Assuan, is a city in the south of Egypt, the capital of the Aswan Governorate.It stands on the east bank of the Nile at the first cataract and is a busy market and tourist centre...
and floated this down the Nile to be used as facing for the pyramids
Egyptian pyramids
The Egyptian pyramids are ancient pyramid-shaped masonry structures located in Egypt.There are 138 pyramids discovered in Egypt as of 2008. Most were built as tombs for the country's Pharaohs and their consorts during the Old and Middle Kingdom periods.The earliest known Egyptian pyramids are found...
. The earliest preserved geologic map
Geologic map
A geologic map or geological map is a special-purpose map made to show geological features. Rock units or geologic strata are shown by color or symbols to indicate where they are exposed at the surface...
was made in 1150 BCE to show the location of gold deposits in Eastern Egypt; it is known as the Turin papyrus
Turin Papyrus
Turin Papyrus refers to any papyrus manuscript in the collection of the Museo Egizio at Turin, Italy. The best known of these manuscripts include:* Turin Papyrus Map* Turin King List* Judicial Papyrus of Turin* Turin Erotic Papyrus...
. The Greek name for Aswan, Syene; is the type locality for the igneous rock
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
syenite
Syenite
Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or...
. The Romans followed this tradition and had many quarries especially in the northern part of the Eastern Desert of Egypt where porphyry
Porphyry (geology)
Porphyry is a variety of igneous rock consisting of large-grained crystals, such as feldspar or quartz, dispersed in a fine-grained feldspathic matrix or groundmass. The larger crystals are called phenocrysts...
and granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
were mined and shaped for shipment. Precious and industrial metals, including gold, silver, copper, zinc, tin, and lead, have been mined in Saudi Arabia for at least 5,000 years. The most productive mine in Saudi Arabia, Mahd adh Dhahab
Mahd adh Dhahab
The Mahd adh Dhahab, also known as the Cradle of Gold, is the leading gold mining area in the Arabian Peninsula. It is located in the Al Madina province of the Hejaz region of Saudi Arabia....
("Cradle of Gold"), has been periodically exploited for its mineral wealth for hundreds or even thousands of years and is reputed to be the original source of King Solomon's gold. Today, mining at Mahd adh Dhahab is conducted by the Saudi Arabian Mining Company, Ma'aden.
Red Sea rifting and exposure of the Arabian-Nubian Shield
The Arabian-Nubian Shield is representative of the continental crustContinental crust
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...
that underlies NE Africa, SW Asia, and Arabia. Geophysical
Geophysics
Geophysics is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and...
studies inform us that ANS crust is about 40–45 km thick, typical for continental crust elsewhere. Geologists are interested to study this crust because it provides an outstanding opportunity to learn how continental crust forms. Elsewhere in Arabia and NE Africa the crust is buried beneath kilometers of younger, Phanerozoic
Phanerozoic
The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared...
sediments and can only be reached by scientific drilling
Scientific drilling
Scientific drilling is a way to probe down into the Earth, allowing scientists and students to obtain samples of sediments, crust, and upper mantle. In addition to rock samples, drilling technology allows humans to obtain samples of connate fluids and of the subsurface biosphere, mostly microbial...
.
Glaciers scoured this land during one of the Neoproterozoic Snowball earth
Snowball Earth
The Snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma . Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical...
episodes (~630 Ma) and the remarkable Arabian-Nubian peneplain
Peneplain
A peneplain is a low-relief plain representing the final stage of fluvial erosion during times of extended tectonic stability. The existence of peneplains, and peneplanation as a geomorphological process, is not without controversy, due to a lack of contemporary examples and uncertainty in...
is overlain by the greatest sand sheet on Earth, the Cambro-Ordovician Siq/Saq sands. This is exposed in spectacular cliffs like the site of Petra
Petra
Petra is a historical and archaeological city in the Jordanian governorate of Ma'an that is famous for its rock cut architecture and water conduits system. Established sometime around the 6th century BC as the capital city of the Nabataeans, it is a symbol of Jordan as well as its most visited...
in Jordan. The Arabian sandstones are overlain by thick deposits of younger sediments that dip and thicken eastwards into the Persian Gulf
Persian Gulf
The Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
. These sands are missing in most of Egypt and Sudan, instead the ANS is overlain by the late Mesozoic Nubian sandstones. All of these sediments were peeled off by erosion to expose the ANS, and much of this sand was reworked by desert winds to make great sand dunes in western Egypt and the Ar Rub al Khali (Empty Quarter
Empty Quarter
The Rub' al Khali or Empty Quarter is one of the largest sand deserts in the world, encompassing most of the southern third of the Arabian Peninsula, including most of Saudi Arabia and areas of Oman, the United Arab Emirates, and Yemen. The desert covers some The Rub' al Khali or Empty Quarter...
) of Arabia.
The embryonic ocean called the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
has slowly widened by rifting over the past 25 million years. Rifting typically causes uplift of its margins, or 'rift shoulders', and the covering sediments were removed by erosion as the Red Sea widened, allowing us to examine the basement geology of this region. This examination is favored also by the desert climate of the region - there is no soil, little vegetation, and few cities or roads to obscure the geology.
Formation of Arabian-Nubian Shield crust
The Arabian-Nubian Shield is the northern half of a great collision zone called the East African Orogen. This collision zone formed near the end of Neoproterozoic time when East and West Gondwana collided to form the supercontinentSupercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. The most intense part of the collision occurred in what is today southern Africa, where older crust in Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
. Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
, and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
was remobilized to form the Mozambique Belt. This great collision was responsible for the Pan-African orogeny
Pan-African orogeny
The Pan-African orogeny was a series of major Neoproterozoic orogenic events which related to the formation of the supercontinents Gondwana and Pannotia about 600 million years ago....
near the end of Neoproterozoic time. The crust of the Mozambique Belt is quite different from that of the Arabian-Nubian Shield, which is predominantly 'juvenile' crust, that is, crust that formed from partial melting of Earth's mantle, although much older Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
and Paleoproterozoic
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
crustal materials is exposed west of the Nile in Egypt, in the SE part of the shield in Arabia, in eastern Ethiopia, and in Yemen.
The ANS took about 300 million years to form. The oldest rocks associated with the formative cycle of the ANS crust formed by coalescence of Island arc
Island arc
An island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates....
s and back-arc basins
Basin (geology)
A structural basin is a large-scale structural formation of rock strata formed by tectonic warping of previously flat lying strata. Structural basins are geological depressions, and are the inverse of domes. Some elongated structural basins are also known as synclines...
and perhaps oceanic plateaus. The oldest rocks associated with this cycle are about 870 million years old and are found in eastern Sudan and SE Arabia. Some of the oldest rocks are ophiolites
Ophiolites
An ophiolite is a section of the Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks...
, which testify that formation of ANS continental crust
Continental crust
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...
began with formation of oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...
by seafloor spreading
Seafloor spreading
Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics....
, followed by the development of subduction zones and Island arc
Island arc
An island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates....
s. The various island arcs collided and these tectonic terranes
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
sutured together during the time period 780 to 620 Ma to form an increasingly broad and thick nucleus of juvenile continental crust. This thickening resulted in the formation of several suture zones
Suture (geology)
In structural geology, a suture is a major fault zone through an orogen or mountain range. Sutures separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories...
, marked by obduction
Obduction
Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks at a convergent plate boundary. It can occur during an orogeny, or mountain-building episode....
of ophiolites and intense deformation. Crustal thickening was also accompanied by melting and magmatic fractionation of mafic magmas that ponded deep in the crust. These melts rose upwards to be emplaced as granitic plutons
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
. Magmatism during this episode is characterized by tholeiite
Tholeiite
The tholeiitic magma series is one of two main magma series in igneous rocks, the other magma series being the calc–alkaline. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it...
s and calc-alkaline
Calc-alkaline
The calc-alkaline magma series is one of two main magma series in igneous rocks, the other magma series being the tholeiitic. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it...
suites.
The welt of juvenile ANS crust was trapped between great tracts of converging continental crust. A protracted episode of continental collision
Continental collision
Continental collision is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together...
started at about 610 Ma ago and continued for about 50 million years. Collision was more intense in the south, in the Mozambique Belt, but it also strongly affected the ANS. N-S oriented upright folds and shear zones deformed the arc terranes and sutures in the southern ANS, forming elongate structures such as the Hamisana Shear Zone in NE Sudan. Farther north and east, the ANS was affected by the formation of the great NW-SE trending Najd system of strike-slip faults. The composition of igneous rocks became distinctively more evolved as the collision continued and the crust continued to thicken. Deep erosion, possibly by a continental ice sheet, happened during this time. All tectonic and magmatic activity ended by the time the Cambrian sandstones were deposited, about 530 million years ago.
A number of features have been ascribed to late stage extensional tectonics
Extensional tectonics
Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere.-Deformation styles:...
including a widespread NE-SW trending dyke
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
swarm, NE-SW trending normal faults and NW-SE trending sedimentary basins filled with post-orogenic molasse
Molasse
The term "molasse" refers to the sandstones, shales and conglomerates formed as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse is deposited in a foreland basin, especially on top of flysch, for example that left from the rising Alps, or erosion in the Himalaya...
deposits
External links
- The Eastern Desert of Egypt in Ancient Times
- The Petra Archeological Park; Petra was carved into lower Paleozoic sandstone.
- Geology of Saudi Arabia
- USGS pamphlet on gold, including early mining in Egypt and Arabia
- Website for the Saudi Geological Survey, which does a lot of work on the Arabian-Nubian Shield.
- UNESCO World Heritage site for St. Catherine monastery area. This is built upon ANS exposures in Sinai.
See also
- ShieldShield (geology)A shield is generally a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. In all cases, the age of these rocks is greater than 570 million years and sometimes dates back 2 to 3.5 billion years...
- CratonCratonA craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
- PlatformPlatform (geology)In geology, a platform is a continental area covered by relatively flat or gently tilted, mainly sedimentary strata, which overlie a basement of consolidated igneous or metamorphic rocks of an earlier deformation...
- BasementBasement (geology)In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...
- Platform basement