Magnetic and grain-size properties of the Weihe River sediments reveal runoff changes in the Holocene

Abstract

Abstract Detailed and systematic analyses of the magnetic and grain-size properties of the Weihe River sediments were conducted to explore effective proxies that could reflect variations in the runoff. Ultimately, the magnetic parameter χARM/χlf was considered a reliable proxy owing to the close relationship with grain-size fraction larger than 63 μm, with a correlation coefficient of 0.90. By combining accelerator mass spectrometry radiocarbon (AMS 14C) dating, a timescale ranging from 12,900 year BP to the present was established for the section. Accordingly, the reconstructed runoff variations showed that, from 12,900 to 9,600 year BP, the hydrodynamic force of the river was relatively strong, and the runoff was large. From 9,600 to 7,500 year BP, these two parameters varied from weak to strong, and the trend continued to increase from 7,500 to 5,300 year BP. At 5,300 year BP, the sediments shifted from the fluvial to the continental environment, indicating a marked decrease in the runoff. Although the resolution and pattern of this reconstruction were rough, this is a significant analysis among the historical runoff studies based on floodplain sediments, and the results showed trends that to some extent coincide with the variations in the intensity of the East Asian Summer Monsoon.