The interplay between climate and tectonics during the upward and outward growth of the Qilian Shan orogenic wedge, northern Tibetan Plateau

Mountains grow upward and outward when the accretion of material outpaces its removal. Mountain building is synergistically influenced by geodynamics, internal structures (crustal and lithospheric), and climate. The northward growth of the Qilian Shan, which occupies a transition zone between the similar to 4500 m high central Tibetan plateau and the adjacent <2000 m high North China craton to the northeast, figures into debates of active orogenic wedge evolution. In this study, we integrate new detrital zircon U-Pb geochronological data with interpretation of seismic profiles and drill core data from the NE Qaidam and Suganhu basins to investigate both the relief building in the Qilian Shan wedge and the source to sink relationship between the Qilian Shan and adjacent basins through time. While intensive crustal shortening within the Qilian Shan during the Paleogene, landward retrogradation of alluvial-fluvial facies in both northeastern and southern Qaidam basin as well as an increasing proportion of Mesozoic to Late Paleozoic and Precambrian detrital zircon ages reveal a basin-scale expansion of drainage area. The connection between the NE Qaidam and the Suganhu basins, as well as the southern Qilian Shan was finally cut off during the Miocene. Combining published regional climate records with provenance data from Cenozoic strata in the Qaidam basin, we infer that increased precipitation under relatively warm and wet climate conditions drove basin-scale transgression during the Paleogene. Since then, the Qaidam basin has been gradually isolated in response to the intensified deformation within the surrounding mountain belts and the regional aridification. We propose the Cenozoic growth of the Qilian Shan could obey critical-taper wedge theory. The climate driven erosion defeated the tectonic thickening in the southern Qilian Shan prior to the Miocene and caused the Qilian Shan wedge to stall. Deformation remained localized in the southern Qilian Shan as wedge taper continued to build. Since the Miocene, decreased erosion of the wedge under arid to semi-arid conditions has allowed deformation to maintain a high enough wedge taper to allow for northward propagation of the deformation front into the central and northern Qilian Shan. This study highlights the significant influence of previously unconsidered regional climate in upward and outward growth in the northern Tibetan plateau. The Cenozoic evolution of northern Tibetan plateau cannot be evaluated without an understanding of how climate may have played into the kinematic history.