Provenance Analysis of Yellow River Terraces Highlights Causes of Siltation and Natural Hazards in the North China Plain

Abstract

AbstractThe avulsion and overflow of river courses during floods, a result of channel siltation above the alluvial plain, is a cause of major natural disasters, including huge property damage and destruction of farmlands. The most sensitive to such risks is the very densely populated area of the Yellow River lower reaches, one of China's most important grain‐producing regions. Problems caused by excessive siltation are a critical issue that should be addressed with full knowledge of sediment‐generation processes, and provenance studies are essential to provide fundamental information for effective environmental management. The Sanmen Gorge is the key region where the great sediment mass produced upstream is conveyed from the middle reaches of the Yellow River to its lower reaches. This study of the terrace sequence exposed along the Sanmen Gorge combines geomorphological observations and provenance analysis based on U‐Pb zircon geochronology and heavy minerals to provide a history of sediment transport through time. The combination of previous research and the outcome of the present study demonstrate that before the Yellow River was formed as an integrated sediment‐routing system, sediments fed into the North China Plain were largely derived from local sources. Instead, after the formation of the Sanmen Gorge, huge quantities of sediment, also derived from the Qinling mountains and stored in the Fenwei basin, were flushed into the North China lowlands by the Yellow River. Such an event took place at 1.2 Ma and has since then impacted severely on floodplain landscape and eventually profoundly affected human activities in the region.