Trans Brazilian Lineament
Encyclopedia
The Trans Brazilian Lineament (TBL), or Transbrasiliano Lineament, is a major shear zone
that developed in the Precambrian
period, and that has been reactivated several times since then, mostly recently during the Mesozoic
. Movement along the shear zone helps explain how the South America
n continent could have fitted tightly to the Africa
n continent before the breakup of Gondwana
.
/ Sao Francisco craton
, was closed during the formation of West Gondwana around 600 million years ago.
The lineament
extends from the northeast coast of Brazil
in a southwesterly direction through Paraguay
and into Argentina
, where it is dissipated in the Salado and Colorado extension basins.
The Trans-Saharan Belt (TSB), running from Algeria
to Benin
, was created in the same period. It marks the line where the Pharusian Ocean
, linked to the Goiás Ocean, was closed as the West African craton
collided with the Saharan Metacraton
.
The TSB includes the Hoggar belt, which splays into the Kandi fault zone
in Benin, corresponding to the Sobral fault
at the north of the TBL.
Given the correspondence of faults, which is widely accepted, the TBL and TBS form perhaps the longest coherent shear zone on the Earth.
in Brazil matches the Foumban fault zone in Cameroon
, and other Brazilian faults match the Benue Trough
in Nigeria
. The extension caused by these spray faults causes a poor fit between South America and Africa around the Niger Delta
region.
However, after allowing for a sinistral shear movement of about 100 km of the crust to the east of the TBL, there is an excellent fit between South America and Africa both to the south and the west of the Niger Delta.
Shear zone
A shear zone is a very important structural discontinuity surface in the Earth's crust and upper mantle. It forms as a response to inhomogeneous deformation partitioning strain into planar or curviplanar high-strain zones. Intervening blocks stay relatively unaffected by the deformation...
that developed in the Precambrian
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...
period, and that has been reactivated several times since then, mostly recently during the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
. Movement along the shear zone helps explain how the South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n continent could have fitted tightly to the Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
n continent before the breakup of 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,...
.
Formation and location
The TBL was formed when the Goiás Ocean, lying between the Amazonian craton and the CongoCongo craton
The Congo craton, covered by the Palaeozoic-to-recent Congo basin, is an ancient Precambrian craton that with four others makes up the modern continent of Africa. These cratons were formed between about 3.6 and 2.0 billion years ago and have been tectonically stable since that time...
/ Sao Francisco craton
Sao Francisco craton
The São Francisco craton is located in the eastern part of South America. Outcrops in the Brazilian states of Minas Gerais and Bahia.It includes a number of different blocks of the Archean basement, separated by orogenic belts. The belts are characterized by sediment basins and passive continental...
, was closed during the formation of West Gondwana around 600 million years ago.
The lineament
Lineament
See also Line A lineament is a linear feature in a landscape which is an expression of an underlying geological structure such as a fault. Typically a lineament will comprise a fault-aligned valley, a series of fault or fold-aligned hills, a straight coastline or indeed a combination of these...
extends from the northeast coast of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in a southwesterly direction through Paraguay
Paraguay
Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...
and into Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, where it is dissipated in the Salado and Colorado extension basins.
The Trans-Saharan Belt (TSB), running from Algeria
Algeria
Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...
to Benin
Benin
Benin , officially the Republic of Benin, is a country in West Africa. It borders Togo to the west, Nigeria to the east and Burkina Faso and Niger to the north. Its small southern coastline on the Bight of Benin is where a majority of the population is located...
, was created in the same period. It marks the line where the Pharusian Ocean
Pharusian Ocean
The Pharusian Ocean is an ancient ocean that existed from 800 to 635 million years ago, between the break-up of the Rodinia supercontinent and the start of formation of the Gondwana supercontinent.-Opening and closure:...
, linked to the Goiás Ocean, was closed as the West African craton
West African craton
The West African craton is one of the five large masses, or 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. These land masses came together in the late Precambrian and...
collided with the Saharan Metacraton
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. Where a craton is an old and stable part of the lithosphere, the term "metacraton" is used to describe a craton that has been remobilized during an orogenic...
.
The TSB includes the Hoggar belt, which splays into the Kandi fault zone
Kandi fault zone
The Kandi fault zone is a southern extension of the Hoggar fault zone in West Africa, with splays in Benin, Togo and southeastern Ghana. It lies at the southern end of the Trans Saharan belt, a lineament that extends in a southwest direction from Algeria to Benin...
in Benin, corresponding to the Sobral fault
Sobral fault
The Sobral fault is a major fault in the Borborema geological province of northeastern Brazil, a part of the Transbrasiliano lineament.It is commonly correlated with the Kandi fault in Benin, east of the West African craton....
at the north of the TBL.
Given the correspondence of faults, which is widely accepted, the TBL and TBS form perhaps the longest coherent shear zone on the Earth.
Gondwana breakup
Towards the north of the lineament in Brazil, a series of splay faults show where the crust has extended, and these faults match corresponding faults in Africa. Thus the Pernambuco faultPernambuco Fault
The Pernambuco fault or Pernambuco Shear Zone in northeastern Brazil is a splay fault radiating from the Transbrasiliano lineament eastwards to the coast, a major geological feature....
in Brazil matches the Foumban fault zone in Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
, and other Brazilian faults match the Benue Trough
Benue Trough
The Benue Trough is a major geological formation underlying a large part of Nigeria and extending about 1,000 km northeast from the Bight of Benin to Lake Chad.It is part of the broader Central African Rift System.-Location:...
in Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
. The extension caused by these spray faults causes a poor fit between South America and Africa around the Niger Delta
Niger Delta
The Niger Delta, the delta of the Niger River in Nigeria, is a densely populated region sometimes called the Oil Rivers because it was once a major producer of palm oil...
region.
However, after allowing for a sinistral shear movement of about 100 km of the crust to the east of the TBL, there is an excellent fit between South America and Africa both to the south and the west of the Niger Delta.