The calcareous tufa in the Tadrart Acacus Mt. (SW Fezzan, Libya). An early Holocene palaeoclimate archive in the central Sahara

The palaeoclimatic significance of calcareous tufa deposits found in the presently hyperarid Tadrart Acacus massif (central Sahara, SW Libya) is discussed on the basis of U/Th datings, stable isotope analyses, and the regional hydrogeological context. These deposits formed mostly between c. 9600 and 8100 yr BP. The isotopic signature (δ18O and δ13C) of this tufa indicates that the water forming these carbonates originated as isotopically depleted rainwater as a result of the northward expansion of the SW African Monsoon system during the early Holocene. Carbonate sedimentation in the Tadrart Acacus decreased shortly before c. 8000 yr BP, attributed to a drop in precipitation in the course of the well known 8.2 kyr event. A correlation between tufa development and climate change in N and E Africa and in the Mediterranean basin during the early Holocene is discussed. The effect of early Holocene climate change on both the landscape and the dwellers living in the Tadrart Acacus region is also evaluated.