0.2 Ma or 1.2 Ma? Timing of the Linking of the Middle and Lower Reaches of the Yellow River Inferred From Loess-Palaeosol Sequences

Variations in susceptibility, grain size or accumulation rates of eolian sequences in the Sanmen Gorge entry and exit points and on the Loess Plateau were compared at different time scales. Synchronous changes in multiple proxies occurred during the formation of S14/L14 at different locality. However, the accumulation rates and magnetic properties were different between the sections in S2 or above, implying that there was significant difference in the proximate source for the gorge entry and exit points. It is suggested that the linking of the middle and lower reaches of the Yellow River occurred at around 1.2 Ma (million years ago) after progressively incising the gorge, while the acceleration in loess accumulation at 0.2 Ma can be attributed to its strong incision in the middle reaches and further channelization in the study area. The entrenchment and terrace formation of the river may be associated with tectonic forcing.