The approximate age of the planation surface and the incision of the Yellow River

Abstract

The Yellow River (Huang He) downstream of the Jinshaan Canyon displays well-preserved fluvial terrace sequences below an extensive planation surface at the northeastern Ordos Plateau. Despite a series of well developed geomorphic surfaces, the landscape evolution of the plateau is largely unconstrained. The Jinshaan Canyon, formed by the deeply incising Yellow River through the Ordos Plateau, provides keys to understanding the landscape evolution of this Plateau with respect to the nearby northeastern margin of the Tibetan Plateau. This paper presents two sets of magnetostratigraphic results derived from the aeolian deposits (Red Clay and loess) on the planation surface and the uppermost Yellow River terrace in the middle part of the Jinshaan Canyon. Magnetostratigraphic analysis reveals that the planation surface and the uppermost Yellow River terrace formed respectively at circa 3.7Ma and circa 1.2Ma ago. The Ordos Plateau is the product of a period of planation culminating just before circa 3.7Ma and then was interrupted by an episode of uplift, which may be correlated with the accelerated growth of the Tibetan Plateau in the Miocene–Pliocene. The drainage system in the Jinshaan Canyon was re-organized around 3.7Ma. No correlation seems to exist between an older drainage existing prior to circa 3.7Ma and the present Yellow River network in the Jinshaan Canyon, even though sedimentary and tectonic evidence suggests that the drainage in the middle reach of the Yellow River formed in the late Miocene-early Pliocene. The Yellow River has developed its rectangular course around the Ordos Plateau only since circa 3.7Ma.