Abstract
The aim of this thesis is to reconstruct the history of the reliefs within the Mongolia-Siberia region, which are the northernmost belts of Central Asia associated with the India-Asia collision. The formation of these belts (Gobi-Altay, Altay and Sayan) is controlled by the activity of large strike-slip faults, associated with reverse segments. These faults reactivate ancient crustal structures. Reliefs are characterized by the preservation of perched flat surfaces (summit plateaus and ancient piedmonts) suggesting a recent uplift. By a morphotectonic and geochronologic approach, we estimate the kinematics and the slip rates of the main faults, as well as the age of the onset of the uplift of the associated reliefs. We describe the morphologic evolution of the of these reliefs and analyze the interactions between the tectonic and climatic processes affecting them.<br />During the Upper Pleistocene – Holocene, the horizontal slip-rates along the Bogd (Gobi-Altay) and Hovd (Altay) strike-slip faults is estimated at ~1mm/yr, while the vertical slip-rates of the reverse segments is estimated at 0.1-0.2 mm/yr. The onset of the uplift of the massifs of the Gobi-Altay and of the eastern Altay appears coeval, and lie between the Latest Miocene and the Lower Pleistocene. These are therefore the youngest reliefs of Central Asia, which is consistent with an ‘in sequence' propagation of the compressive deformation from the himalyan front. These massifs also record a jurassic-cretaceous tectonic event, associated with local vertical movements higher than 2 km. The erosion consecutive to this episode led to the formation of a large peneplain, whose relicts form the summit surfaces of the mongolo-siberian massifs.