River Morphologies and Palaeodrainages of Western Africa (Sahara and Sahel) During Humid Climatic Conditions

  1. Gary Nichols,
  2. Ed Williams and
  3. Chris Paola
  1. Gian Gabriele Ori,
  2. Gaetano Diachille,
  3. Goro Komatsu,
  4. Lucia Marinangeli and
  5. Angelo Pio Rossi

Published Online: 30 MAR 2009

DOI: 10.1002/9781444304411.ch20

Sedimentary Processes, Environments and Basins: A Tribute to Peter Friend

Sedimentary Processes, Environments and Basins: A Tribute to Peter Friend

How to Cite

Ori, G. G., Diachille, G., Komatsu, G., Marinangeli, L. and Rossi, A. P. (2007) River Morphologies and Palaeodrainages of Western Africa (Sahara and Sahel) During Humid Climatic Conditions, in Sedimentary Processes, Environments and Basins: A Tribute to Peter Friend (eds G. Nichols, E. Williams and C. Paola), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304411.ch20

Author Information

  1. International Research School of Planetary Sciences, Universita' d'Annunzio, Viale Pindaro 42, 65127 Pescara, Italy

  1. lbn Battuta Centre, Faculté des Sciences Semlalia, Université Cadi Ayyad, Marrakech, Morocco

  2. ESTEC, European Space Agency, Noordwijk, The Netherlands

Publication History

  1. Published Online: 30 MAR 2009
  2. Published Print: 7 DEC 2007

Book Series:

  1. Special Publication Number 38 of the International Association of Sedimentologists

Book Series Editors:

  1. Ian Jarvis

Series Editor Information

  1. School of Earth Sciences & Geography, Centre for Earth & Environmental Science Research, Kingston University, Penrhyn Road, Kingston upon Thames KT1 2EE, UK

ISBN Information

Print ISBN: 9781405179225

Online ISBN: 9781444304411

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Keywords:

  • river morphologies and palaeodrainages of western Africa (Sahara and Sahel);
  • palaeoriver systems;
  • Niger system and Azaouad;
  • Erg Chech and Tanezrouft;
  • palaeovalleys and large palaeorivers in western Sahara;
  • tectonic movement role in changes of river patterns and effects on climatic changes

Summary

River systems in desert regions are basically of two types: ephemeral streams and exotic (or allogenic) rivers. In contrast to ephemeral streams, exotic rivers are perennial and survive hydrological crisis. Unique features of exotic rivers are their inland deltas, where they form intricate patterns of small channels and lose a large part of their water. Extensive exotic rivers flowed in the Sahara during wet climatic periods, and they have left a large number of dry streams and palaeovalleys. Most of these ancient courses are at the present time ephemeral streams or they are now totally inactive. During wet climatic periods the Niger River, for example, was split into two unconnected reaches: the upper reach flowed to the north, forming a large inland delta in the area of Azouad (north of Timbuktu); the lower reach flowed to the south, from the Adrar des Iforhas and Air. The upper part of this southward flowing system is now dry, and corresponds to the palaeovalley of Azaouak and adjacent palaeovalleys. During wetter climatic periods, the Sahara was covered by lakes and swamps in the deepest parts of the inland basins. These lakes were supplied by exotic rivers forming deltas at their mouths. The rivers formed palaeovalleys that are now inactive or are occupied by ephemeral streams with episodic floods, and terminal fans have replaced the original deltaic systems.