Hydroclimate change during the transition of mid-to late Holocene and its potential impacts on late Neolithic settlements in middle Yangtze Basin, Central-South China

The history and spatial variations of hydroclimatic change in East Asia during the transition from the middle to late Holocene remain inadequately understood. Furthermore, the impacts of these hydroclimatic changes on ancient civilizations across various regions of eastern China have yet to be fully elucidated. In this study, we utilize precisely dated multi-proxy stalagmite records from Yuwang Cave to reveal the temporal and spatial variations of hydroclimate in central-south China during 6.0–4.0 ka BP, as well as to unravel potential impacts of these changes on the development of late Neolithic cultures in the middle Yangtze Basin. The records indicate that there was an increasing trend in stalagmite δ¹⁸O values from ∼6.0 ka BP to 4.0 ka BP, suggesting that an evident decline in summer monsoon intensity occurred. In contrast to δ¹⁸O, the δ¹³C values remained relatively stable during 6.0–4.5 ka BP but abruptly increased and sustained higher levels during 4.5–4.2 ka BP before experiencing a dramatic decrease with lower values during 4.2–4.0 ka BP; growth rates and Mg/Ca ratios exhibited synchronous changes alongside δ¹³C, indicating significant shifts in dry-wet conditions throughout central-south China during the transition of mid-to-late Holocene. Notably, the drier yet more stable climatic phase between 4.5 and 4.2 ka BP coincided closely with the flourishing of the Shijiahe Culture in the middle Yangtze Basin - providing new evidence that declining monsoonal rainfall may have facilitated the expansion of late Neolithic settlements in lowland areas of the Basin around the 4.2 ka event. Taking robust geological records from other parts of eastern China together, we found that the hydroclimatic pattern of eastern China during 4.5–4.2 ka BP did not conform to dipole nor tripole modes; rather it exhibited a more complex pattern characterized by “dry conditions prevailing in both middle-lower Yangtze Basin and North China, while the middle-lower Yellow River Basin alongside Southeastern China experienced wetness”. This precipitation pattern was probably associated with the weakened East Asian summer monsoon coupled with strong Atlantic meridional overturning circulation, positive Pacific decadal oscillation, and damped El Niño-Southern Oscillation (ENSO) activity with a La Niña-like state that occurred within the southeastern tropical Pacific