Pleistocene opening of the Ouarzazate Basin, and incision rate history of the Draa canyon in the Anti-Atlas of Morocco revealed by 10Be cosmogenic nuclide dating and non-linear river profile inversion

Abstract

Records of incision history such as topographic data and landform dating can be gathered in inversion schemes to reconstruct base-level fall and uplift history. Here, we use a non-linear inversion scheme and the stream power incision model to study the landscape evolution of a mountainous area to quantify whether it responds to an uplift or a capture-induced local base-level fall. Our inversion is constrained by 10Be cosmogenic nuclide data. The probabilistic approach yields an ensemble of solutions made by a combination of model parameters. We apply our model to the Draa Canyon located in the Anti-Atlas of Morocco at the outlet of the Ouarzazate Basin which was internally drained during the Miocene. We show that incision rates in the Ouarzazate Basin and the southern margin of the High Atlas are compatible with a Pleistocene age for the opening of the Basin. The forcing to drainage integration may be due to capture by regressive erosion in the proto Draa river or tilting to the south of the High Atlas, Ouarzazate basin, and Anti-Atlas as a whole in response to mantle-related continental-scale uplift, or a combination of both. The southern border of the High Atlas in this region displays a transient landscape previously interpreted as evidence for recent shortening and rock uplift. Our results suggest that the rejuvenation of the southern Central High Atlas, in the northern margin of the Ouarzazate Basin, mainly occurred in response to the opening of the Ouarzazate Basin, with only several hundreds of meters of rock uplift localized along the South Atlas front during the late Cenozoic.