Assertion: second zone | /r/MadeOf | primary sandstone
Facets:
value: in the north
type: LOCATION
Source sentences:
text: In the north it consists of primary sandstone, which covers the Tindouf Syncline (a fold in the rocks in which the strata dip inward from both sides toward the axis); in the centre is the vast synclinal basin of Taoudeni, bounded by the Adrar, Tagant, and ʿAçâba (Assaba) plateaus.