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Central Africa showing the interpreted extent of the 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.Vorlage:Sfn The structure is not well understood. Vorlage:As of, there was still no general agreement about how the individual shears along the lineament link up.Vorlage:Sfn

Description Bearbeiten

The shear zone dates to at least 640 Ma (million years ago).Vorlage:Sfn Motion occurred along the zone during the break-up of Gondwanaland in the Jurassic and Cretaceous periods.Vorlage:Sfn Some of the faults in the zone were rejuvenated more than once before and during the opening of the South Atlantic in the Cretaceous period.Vorlage:Sfn

It has been proposed that the Pernambuco fault in Brazil is a continuation of the shear zone to the west.Vorlage:Sfn 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.Vorlage:Sfn 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.Vorlage:Sfn 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.Vorlage:Sfn The Mesozoic and Tertiary movements have produced elongated rift basins in central Cameroon, northern Central African Republic and southern Chad.Vorlage:Sfn

Sudan Bearbeiten

The CASZ was formerly thought to extend eastward only to the Darfur region of western Sudan.Vorlage:Sfn It is now interpreted to extend into central and eastern Sudan, with a total length of 4,000 km.Vorlage:Sfn In the Sudan, the shear zone may have acted as a structural barrier to development of deep Cretaceous-Tertiary sedimentary basins in the north of the area. Objections to this theory are that the Bahr el Arab and Blue Nile rifts extend northwest beyond one proposed line for the shear zone.Vorlage:Sfn However, the alignment of the northwestern ends of the rifts in this areas supports the theory.Vorlage:Sfn

References Bearbeiten

Vorlage:Reflist Vorlage:Refbegin

Sources books Bearbeiten

  • Robert Bowen, Ulrich Jux: Afro-Arabian geology: a kinematic view. Springer, 1987, ISBN 0-412-29700-0 (google.com).
  • C. Dorbath, L. Dorbath, J. D. Fairhead, G. W. Stuart: A teleseismic delay time study across the Central African Shear Zone in the Adamawa region of Cameroon, West Africa. In: Geophysical Journal International. 86. Jahrgang, Nr. 3, 1986, S. 751–766, doi:10.1111/j.1365-246x.1986.tb00658.x, bibcode:1986GeoJ...86..751D.
  • Gillian R. Foulger, Donna M. Jurdy: Plates, plumes, and planetary processes. Geological Society of America, 2007, ISBN 978-0-8137-2430-0 (google.com).
  • A. E. Ibrahim, C. J. Ebinger, J. D. Fairhead: Lithospheric extension northwest of the Central African Shear Zone in Sudan from potential field studies. In: Tectonophysics. 255. Jahrgang, s 1-2, 20. April 1996, S. 79–97, doi:10.1016/0040-1951(95)00080-1, bibcode:1996Tectp.255...79I.
  • Robert J. Pankhurst: West Gondwana: pre-Cenozoic correlations across the South Atlantic Region. Geological Society, 2008, ISBN 978-1-86239-247-2.
  • J Plomerova, V Babuska, C. Dorbath, L. Dorbath, R. J. Lillie: Deep lithospheric structure across the Central African Shear Zone in Cameroon. In: Geophysical Journal International. 115. Jahrgang, Nr. 2, 1993, ISSN 0956-540X, S. 381–390, doi:10.1111/j.1365-246x.1993.tb01193.x, bibcode:1993GeoJI.115..381P.
  • Richard C. Selley: African basins. Elsevier, 1997, ISBN 0-444-82571-1 (google.com).
  • Thomas Schlüter, Martin H. Trauth: Geological atlas of Africa: with notes on stratigraphy, tectonics, economic geology, geohazards, geosites and geoscientific education of each country. シュプリンガー・ジャパン株式会社, 2008, ISBN 978-3-540-76324-6 (google.com).

Vorlage:Refend

Vorlage:Major African geological formations [[Category:Seismic faults of Africa]] [[Category:Geology of Africa]] [[Category:Geology of Cameroon]] [[Category:Geology of the Central African Republic]] [[Category:Geology of South Sudan]] [[Category:Geology of Sudan]] [[Category:Geography of Cameroon]] [[Category:Geography of the Central African Republic]] [[Category:Geography of South Sudan]] [[Category:Geography of Sudan]] [[Category:Cretaceous Africa]] [[Category:Shear zones]]