Northeastward growth and uplift of the Tibetan Plateau: Magnetostratigraphic insights from the Guide Basin

Most of the evidence for the uplift of the Tibetan Plateau comes from its southern and central parts. Although the northern rim has been less studied, it may greatly contribute to the understanding of the mechanism and timing of the uplift. Recent studies on the northeastern part of the plateau suggest that the uplift can largely be explained by Cenozoic thrusting and folding linked to the movement of the Altyn Tagh and Kunlun faults and that diffuse shortening might be a realistic way to explain the thickening of the continental interior. Nevertheless, the age of sediments that record the tectonic processes is poorly known. The terrigenous formations in the Guide-Gonghe Basin, NE Tibet, show several phases of deformation and include thick deposits of conglomerates, interbedded with sandstones and siltstones that are thought to be the result of an increased sediment flux. Dating of these gravel deposits with magnetostratigraphic and faunal studies has permitted the precise timing of the basin infilling and its tectonic evolution to be established. Our results indicate that the onset of conglomerate accumulation occurs in the Pliocene, an observation that is in agreement with those of the Linxia Basin, just east of the Plateau. If the high sedimentation rates (similar to22 cm/kyr) in the Guide Basin are mostly due to tectonism, then significant uplift occurred as late as Pliocene.