The Taoudeni is the largest sedimentary basin in Northwest Africa, formed during the mid-late Proterozoic. It continued to subside until the mid-Paleozoic age, when Hercynian deformation and uplift occurred. It contains up to 6000 m of Late Precambrian and Paleozoic sediments. Exploratory drilling since the 1980s has found indications of petroleum in the Late Precambrian, Silurian and Late Devonian layers. Sediments are thicker in the western half of the basin.