The Foumban Shear Zone, or Central Cameroon Shear Zone (CCSZ), is a fault zone in

Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...

that has been correlated with the Pernambuco fault in northeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, which splays from the Trans-Brazilian Lineament. It is part of 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 ...

(CASZ) and dates to at least 640 million years ago. The zone was rejuvenated several times, usually with a

dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

movement, before and during the opening of the South Atlantic in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period. The Foumban shear zone is a series of faults associated with major

mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a ...

zones, a segment of the CASZ. The CASZ can be traced from the

Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...

to the

Adamawa plateau The Adamawa Plateau () is a plateau region in west-central Africa stretching from south-eastern Nigeria through north-central Cameroon ( Adamawa and North Provinces) to the Central African Republic. The part of the plateau that lies in Nigeria i ...

, after which its path is obscured by volcanoes. Based on reconstruction of the configuration of South America before it separated from Africa, the zone can be identified with the Pernambuco fault. The shear zone underlies a chain of active volcanoes, called the Cameroon Volcanic Line. In August 1986 a magnitude 5 earthquake with epicenter near

Lake Nyos Lake Nyos ( ) is a crater lake in the Northwest Region of Cameroon, located about northwest of Yaoundé, the capital. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcan ...

indicated that the shear zone may be again reactivating.

References

Geology of Africa Seismic faults of Africa Shear zones {{palaeo-geo-stub