Late Holocene variations and driving mechanisms of the East Asian summer monsoon in northern margins: Evidence from peat ash grain size

East Asian summer monsoon (EASM) played key role in controlling the hydroclimate of East Asia continent regions. However, the Late Holocene changes of EASM in its northern margins are still unclear, which urgently needs to be revealed in the field of climate research. Here we systematically analyze the grain size of peat ash from core ZB-7 in the Zhibian peatland and core DFHN-2 in the Dongfanghongnan peatland to address this issue. Results show that the silt fraction occupies the most component of peat ash in cores ZB-7 and DFHN-2. The grain size distribution curves of peat ash of two cores display single peak pattern. The probability cumulative curves of two cores exhibit as two-sections mode. Three end-members (EMs) displaying single peak are identified in cores ZB-7 and DFHN-2. The EM2 of core ZB-7 and EM1 of core DFHN-2 represent the contributions of surface runoff. The EM2 of core ZB-7 demonstrates a series of periodicities, such as 1000a, 500a, 210a, 110a, 88a and 66a during the Late Holocene. The correlation relationship analyses indicate that the EM2 of core ZB-7 and total solar insolation (TSI) show opposite phase with El Niño-Southern Oscillation (ENSO) activities. Furthermore, five evolutionary stages of the EASM in northern margins were identified. Less ENSO activities and declined TSI regulated the decreased precipitation during stage 1 (4338-3479 cal. yr BP). The frequent ENSO activities and declined TSI induced low precipitation in stage 2 (3479-2297 cal. yr BP). In stage 3 (2297-949 cal. yr BP), the continuously decreasing ENSO activities resulted in high precipitation. Frequent ENSO activities and low TSI induced low precipitation during stage 4 (949-231 cal. yr BP). While the increase in TSI and decrease in ENSO activities regulated increased precipitation during stage 5 (231 cal. yr BP-Present). This study would expand our predictions on the future hydroclimate changes in monsoon northern margins.