Hydrological regime responses to Holocene East Asian summer monsoon circulation in marshes of the Sanjiang Plain, NE China

In this paper, grain-size records of 128 surface samples and six sediment cores retrieved from freshwater marshes across the Sanjiang Plain were employed to reconstruct the marshes' hydrological variation during the Holocene and to discuss its links to the East Asian summer monsoon (EASM) variation. The grain-size hydrological significance for the marshes' deposits was first interpreted by quantitative analyses of 128 modern samples. The results indicate that the sand fraction exhibits a higher level significance to modern water-level conditions than other grain-size parameters. Thus, the sand accumulation rates of the six cores were calculated and employed to reconstruct the Holocene hydrological regime of the marshes on the plain. Based on the cluster analysis, it can be identified that three higher water-level stages occurred during 6.2-5.6 thousand yr BP, 5.6-4.5 thousand yr BP, and 2.8-2.4 thousand yr BP, whereas four lower water-level stages occurred during similar to 8.0-6.2 thousand yr BP, 4.5-2.8 thousand yr BP, 2.4-0.7 thousand yr BP, and 0.7-0 thousand yr BP, respectively. Considering the prevalent monsoon climate on the modern Sanjiang Plain, it is reasonable to believe that the local water-level fluctuations were mainly regulated by the EASM variation rather than local factors including flooding, waterway modification, depression infilling, and human activities. The higher water-level stages were linked to a stronger EASM and vice versa. This study provides essential background datasets for understanding the potential controls on the marsh development and degradation on the Sanjiang Plain.