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Central African Shear Zone

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Title: Central African Shear Zone  
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Central African Shear Zone

Central Africa showing CASZ
Rifts in Sudan and Kenya

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.[1] The structure is not well understood. As of 2008 there was still no general agreement about how the individual shears along the lineament link up.[2]

Description

The shear zone dates to at least 640 MA (million years ago).[3] Motion occurred along the zone during the break-up of Gondwanaland in the Jurassic and Cretaceous ages.[1] Some of the faults in the zone were rejuvenated more than once before and during the opening of the South Atlantic in the Cretaceous era.[3]

The Pernambuco fault in Brazil is a continuation of the shear zone to the west.[3] In Cameroon, the CASZ cuts across the Adamawa uplift, a post-Cretaeous formation. The Benue Trough lies to the north, and the Foumban Shear Zone to the south.[4] Volcanic activity has occurred along most of the length of the Cameroon line from 130 MA to the present, and may be related to re-activation of the CASZ.[5] The lithosphere beneath the CASZ in this area is thinned in a relatively narrow belt, with the asthenosphere upwelling from a depth of about 190 km to about 120 km.[6] The Mesozoic and Tertiary movements have produced elongated rift basins in central Cameroon, northern Central African Republic and southern Chad.[3]

Sudan

The CASZ was formerly thought to extend eastward only to the Darfur region of western Sudan.[3] It is now known to extend into central and eastern Sudan, with a total length of 4,000 km.[1] In the Sudan, the shear zone may have acted as a structural barrier to development of deep Cretaceous-Terriary sedimentary basins in the north of the area.

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