The impact of faulting-induced uplift and subsidence on terrace formation and abandonment: a case study of the Huangshui River, NE Tibetan Plateau

Abstract

Fluvial terraces are important archives for inferring changes in river dynamics. In the NE Tibetan Plateau, the Huangshui River flows through broad depressions and narrow gorges. This morphology is the result of strike-slip and reverse faulting. Differential vertical motion has led to the formation of diverse fluvial terraces. We used morphological analyses, sedimentary successions and optically stimulated luminescence dating to map, characterize and date fluvial terraces in two depressions and the connecting gorge. Our results show that an important phase of tectonism occurred shortly after 138 ka because: (1) terraces older than 138 ka in the gorge show clear deformation in their longitudinal profiles; (2) terraces from the last interglacial are composed of a thick fill terrace in the upstream depression, a strath terrace in the gorge and a fill terrace created by an alluvial fan in the downstream depression; and (3) the aggradation of the last interglacial terrace began synchronously in the upstream and downstream depressions, whereas the abandonment age becomes younger in an upstream direction (from c. 131 to c. 91 ka). The transient abandonment reflects an upstream-migrating knickpoint. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change