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 (\u3b418O and \u3b413C) 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

Progressive offset and surface deformation along a seismogenic blind thrust in the Po Plain foredeep (Southern Alps, Northern Italy)

Here we present, for the first time in the Po Plain foredeep (Northern Italy), the middle to late Pleistocene growth history of an outcropping secondary fold and related faults, whose progressive deformation over an intermediate time window (105\u2009years) is driven by an underlying seismogenic blind thrust. We trenched and logged an outcropping decametric secondary anticline, related to a deeper blind compressional structure, which deforms fluvial sediments and an overlying loess-paleosol sequence. Folded units were dated, using radiocarbon and optically stimulated luminescence methods, to the late Pleistocene\u2013Holocene and tentatively correlated with glacial-interglacial phases occurring during the time interval from marine isotope stage 6 to the present. A multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline, varying between 0.02 and 0.1\u2009mm/yr since circa 200 kyr. Trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break-backward activation. This generated a decametric surface fold whose most recent growth was associated with bending-moment normal faulting in the crestal and forelimb region. Our observations demonstrate that near-surface compressive tectonics can be caused by blind thrusting, via a complex array of fault and folds: upward strain propagation and generation of shallow low-angle thrust and related folding seem to be mainly due to secondary fold-related faulting, according to an out-of-syncline thrusting mechanism