Mid-Holocene environmental change and its impact on human settlement in the eastern Jianghuai region of coastal China: Mineralogical and geochemical evidence

Holocene environmental changes in the eastern Jianghuai region of coastal China were driven by climate variability, sea-level fluctuations, and the evolution of the palaeo-Huai River Delta, making the region a key nexus for Neolithic cultural interactions between societies in the lower basins of Yangtze and Yellow rivers. Unravelling how environmental dynamics shaped human activities here provides valuable insights into past human–environment interactions and their broader implications. In this study, we conducted detailed mineralogical and geochemical analyses of mid-Holocene sediments from a profile situated in the palaeo-Huai River Delta, to reconstruct past environmental changes. Elevated Sr/Ba ratios, together with authigenic gypsum and pyrite, indicate brackish water intrusion between 7400 and 6700 cal. yr before present (BP), consistent with the event of accelerated global sea-level rise. A subsequent long-term drying trend from 6700 to 3000 cal. yr BP is reflected in declining Clay/Quartz ratios and TOC contents, as well as enriching δ¹³C_org, while the recovery in Clay/Quartz ratios indicates climatic amelioration during 6000–4400 cal. yr BP. These environmental shifts shaped human settlement patterns and cultural development, with population growth closely linked to warmer and more humid conditions. In addition, landscape features including the palaeo-Huai River Delta and chenier ridges likely further promoted human settlements. Our findings highlight the combined influence of climate and landscape on demographic evolution in the coastal lowlands.