The Pan-African orogeny was a series of major
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago.
It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...
orogenic events which related to the formation of the
supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
s
Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
and
Pannotia
Pannotia (from Greek: '' pan-'', "all", '' -nótos'', "south"; meaning "all southern land"), also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontinent ...
about 600 million years ago. This orogeny is also known as the Pan-Gondwanan or Saldanian Orogeny. The Pan-African orogeny and the
Grenville orogeny
The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, f ...
are the largest known systems of orogenies on Earth.
The sum of the
continental crust
Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...
formed in the Pan-African orogeny and the Grenville orogeny makes the Neoproterozoic the period of Earth's history that has produced most continental crust.
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History and terminology
The term ''Pan-African'' was coined by for a tectono-thermal event at about 500 Ma when a series of mobile belts in Africa formed between much older African craton
A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...
s. At the time, other terms were used for similar orogenic events on other continents, i.e. '' Brasiliano'' in South America; ''Adelaidean'' in Australia; and ''Beardmore'' in Antarctica.
Later, when plate tectonics
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...
became generally accepted, the term ''Pan-African'' was extended to all of the supercontinent Gondwana. Because the formation of Gondwana encompassed several continents and extended from the Neoproterozoic to the early Palaeozoic, ''Pan-African'' could no longer be considered a single orogeny, but rather an orogenic cycle that included the opening and closing of several large oceans and the collisions of several continental blocks. Furthermore, the Pan-African events are contemporaneous with the Cadomian orogeny in Europe and the Baikalian orogeny in Asia, and crust from these areas were probably part of Pannotia (i.e. Gondwana when it first formed) during the Precambrian.
Attempts to correlate the African Pan-African belts with the South American Brasiliano belts on the other side of the Atlantic has in many cases been problematic.
Pan-African belts
Orogenic belts comprising the Pan-African system include:
* The Arabian-Nubian Shield
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 parts of Israel, Jo ...
, extending from Ethiopia to the southern Levant, it is associated with the opening of the Red Sea
The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...
.
* The Mozambique Belt
The Mozambique Belt is a band in the earth's crust that extends from East Antarctica through East Africa up to the Arabian-Nubian Shield. It formed as a suture between plates during the Pan-African orogeny, when Gondwana was formed.
The Mozambiq ...
, extending from east Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
through East Africa
East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa:
Due to the historical ...
up to the Arabian-Nubian Shield
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 parts of Israel, Jo ...
, formed as a suture between plates during the Pan-African orogeny. The Mozambique ocean began closing between Madagascar-India and the Congo-Tanzania
Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...
craton between 700 and 580 million years ago, with closure between 600 and 500 million years ago.
* The Zambezi Belt
The Zambezi Belt is an area of orogenic deformation in southern Zambia and northern Zimbabwe. It is a segment of a broader belt lying between the Congo Craton and the Kalahari Craton, which also includes the Lufilian Arc and the Damaran Belt.
The ...
branches off the Mozambique Belt in northern Zimbabwe and extends into Zambia.
* The Damara Belt
The Damara orogeny was part of the Pan-African orogeny. The Damara orogeny occurred late in the creation of Gondwana, at the intersection of the Congo and the Kalahari cratons.; ; ; ;
The Damara orogeny involved the suturing of the Congo– S ...
is exposed in Namibia between the Congo and Kalahari
The Kalahari Desert is a large semi-arid sandy savanna in Southern Africa extending for , covering much of Botswana, and parts of Namibia and South Africa.
It is not to be confused with the Angolan, Namibian, and South African Namib coastal de ...
cratons and continues southwards into the coastal Gariep and Saldania Belts and northwards into the Kaoko Belt. It is the result of closure of the Adamastor
Adamastor is a mythological character created by the Portuguese poet Luís de Camões in his epic poem ''Os Lusíadas'' (first printed in 1572), as a personification of the Cape of Good Hope, symbolizing the dangers of the sea and the formidable ...
and Damara oceans and includes two horizons associated with a severe equator-ward glaciation explained by the Snowball Earth hypothesis.
* The Lufilian Arc
The Lufilian Arc (or Lufilian Belt) is part of a system of orogenic belts in southern Africa formed during the Pan-African orogeny, a stage in the formation of the Gondwana supercontinent.
It extends across eastern Angola, the Katanga Province of ...
is most likely a continuation of the Damara Belt in Namibia to which it connects in northern Botswana. It is a broad arc reaching as far north as the southern DRC and Zambia.
* The Gariep
The Orange River (from Afrikaans/Dutch: ''Oranjerivier'') is a river in Southern Africa. It is the longest river in South Africa. With a total length of , the Orange River Basin extends from Lesotho into South Africa and Namibia to the nort ...
and Saldania belts run along the western and southern edge of the Kalahari Craton. Also the result of the closure of the Adamastor Ocean, the marine deposits, seamounts, and, ophiolite
An ophiolite is a section of 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.
The Greek word ὄφις, ''ophis'' (''snake'') is found ...
s they contain were accreted onto the Kalahari margin around 540 Ma. They include the granite at Sea Point, Cape Town
Sea Point (Afrikaans: ''Seepunt'') is one of Cape Town's most affluent and densely populated suburbs, situated between Signal Hill and the Atlantic Ocean, a few kilometres to the west of Cape Town's Central Business District (CBD). Moving from ...
visited by Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
in 1836.
* The Kaoko Belt branches north-west from the Damara Belt into Angola. Also produced by the closure of the Adamastor Ocean, this belt includes a shear zone known as the 733-550 Ma-old Puros lineament in southern Angola. It contains 2030-1450 Ma-old, strongly deformed basement
A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...
rocks, probably derived from the Congo Craton, mixed with Late Archaean granitoid gneisses of unknown origin. No island arcs or ophiolote are known from the Kaoko Belt.
* The West Congo Belt is the product of 999-912 Ma-old rifting along the western margin of the Congo Craton followed by the formation of a foreland basin
A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...
onto which the belt was deposited 900-570 Ma. In the western belt allochthon
upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a nappe. If an erosional hole is created in the nappe that is called a window (geology)">window. A klippe is a solitary out ...
ous Palaeo- and Mesoproterozoic basement rocks override the foreland sequence. It includes glacial deposits similar to those in the Lufilian Arc and is conjugate to the Araçuaí Belt
Araçuaí is a Brazilian municipality located in the northeast of the state of Minas Gerais in the Jequitinhonha River valley. The Araçuaí River, a tributary of the Jequitinhonha, flows through it. Its population was estimated to be 36,712 peo ...
in Brazil.
* The 3000 km-long Trans–Saharan Belt runs north and east of the more than 2000 Ma-old West African Craton
The West African Craton (WAC) is one of the five cratons of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton.Jessell M.W., Liégeo ...
bordering the Tuareg
The Tuareg people (; also spelled Twareg or Touareg; endonym: ''Imuhaɣ/Imušaɣ/Imašeɣăn/Imajeɣăn'') are a large Berber ethnic group that principally inhabit the Sahara in a vast area stretching from far southwestern Libya to southern A ...
and Nigerian
Nigerians or the Nigerian people are citizens of Nigeria or people with ancestry from Nigeria. The name Nigeria was taken from the Niger River running through the country. This name was allegedly coined in the late 19th century by British jour ...
shields. It consists of a strongly deformed pre-Neoproterozoic basement and Neoproterozoic oceanic rocks containing ophiolite, accretionary prisms, arc-related and high-pressure metamorphic rocks dated to 900-520 Ma.
* The Central African belts between the Congo and Nigerian shields consists of Neoproterozoic rocks and deformed granitoids interlayered with wedges of Palaeoproterozoic basement. The southern part is the product of a continental collision during which it was thrusted onto the Congo Craton. The central and northern parts are thrust-and-shear zones correlated with similar structures in Brazil. The belts in Central Africa continue east as the Oubanguide Belt with which they form the Central African Shear Zone
The Central African Shear Zone (CASZ) (or Shear System) is a wrench fault system extending in an ENE direction from the Gulf of Guinea through Cameroon into Sudan.
The structure is not well understood.
, there was still no general agreement about ...
.
* The Saharan Metacraton
The Saharan Metacraton is a term used by some geologists to describe a large area of continental crust in the north-central part of Africa. Whereas a craton is an old and stable part of the lithosphere, the term "metacraton" is used to describe a ...
between the Hoggar Mountains
The Hoggar Mountains ( ar, جبال هقار, Berber: ''idurar n Ahaggar'') are a highland region in the central Sahara in southern Algeria, along the Tropic of Cancer. The mountains cover an area of approximately 550,000 km.
Geography
This ...
and the Nile
The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...
river consists of an Archaean-Palaeoproterozoic basement overprinted by Pan-African granitoids.
* The Rokelide Belt passes along the western margin of the Archaean Man Shield
The Man Shield (Leo-Man Shield or Leo-Man Craton) is a geological shield or craton in the southeast portion of the West African Craton. The shield is in part overlaid by gold-bearing Birimian formations.
Geography and Geology
The shield co ...
in the southern West African Craton. It was intensely deformed during the Pan-African orogeny with a peak reached around 560 Ma and can be an accretionary belt.
References
Sources
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{{Major African geological formations
Orogenies of Africa
Orogenies of South America
Neoproterozoic Africa
Neoproterozoic South America
Neoproterozoic orogenies