The Tuareg Shield is a geological formation lying between the West African craton and the Saharan Metacraton in West Africa. Named after the Tuareg people, it has complex a geology, reflecting the collision between these cratons and later events. The landmass covers parts of Algeria, Niger and Mali.
The Tuareg Shield is mainly composed of Archean or Paleoproterozoic terranes and Neoproterozoic terranes that amalgamated during the Pan African orogeny when the West African craton and the Saharan metacraton converged.
In Mali, the Tilemsi belt is a complex of intraoceanic arcs that formed above a subduction zone sloping down to the east and were accreted to the shield during the Pan-African orogeny. The western part of the Hoggar Mountains (Ahaggar Mountains) is made of material from the Pharusian Ocean.
This comprises oceanic basalts, arc volcanic and sedimentary rocks and sediments, which were shed into the Pharusian Ocean by the West African craton and the eastern Hoggar.
During the oblique collision of the West African craton with the Saharan metacraton the shield was torn into separate but rigid moving blocks. These blocks were separated by subvertical shear zones.
At the start of the Phanerozoic the shield was eroded and covered by Ordovician sandstones. More recently, around 95 Ma - 90 Ma, the area was partly submerged by a seaway linking the Mediterranean and the proto-Atlantic. Since then, starting around 30 Ma the area rose by as much as 3000 meters.
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