Evolution of fluvial landscapes since the late Pleistocene at the Wangchenggang site of the Ying River Basin, Central China: Implications for the development and change of prehistoric settlements

Reconstructing the evolution of fluvial landscapes is vital to our understanding of how and why early settlements used or abandoned locations in dynamic alluvial settings, especially places such as China's Central Plains where alluvial landforms have dominated since at least the late Pleistocene era. The Wangchenggang (WCG) site on the upper reaches of the Ying River is considered to be the legendary capital of the Great Yu who, according to historical documents, heroically tamed the big floods and founded the first dynasty of Xia. However, evolution of the alluvial landscape of the Holocene Ying River and its influence on the long-term settlement change at the WCG site remains unclear. We present a detailed reconstruction of long-term landscape evolution and settlement change at the site, based on the results of our geoarchaeological investigation, and published paleoclimate and archaeobotanical data. The results show that the region experienced an episode of extensive alluvial accretion in the late Pleistocene. From the end of the late Pleistocene to the early Holocene, the Ying River began to incise the alluvial plain, leading to the formation of the oldest terrace (T3). The middle and late Holocene in the Ying River valleys saw two episodes of alluvial aggradation between 7.7–5.4 ka B.P. (before present) and 4.5–3.8 ka B.P., respectively. Each of these events was followed by an alluvial incision, resulting in the formation of new alluvial terraces. During the historical periods, the youngest terrace T1 was formed. These cyclic changes in the regional fluvial landscape profoundly impacted the location and expansion of prehistoric settlements. During the Peiligang period (9.0–7.0 ka B.P.), the early stages of alluvial aggregation resulted in wide and shallow channels along the rivers. Early humans who relied on gathering and hunting for food chose to establish small settlements along such riverine environments. As alluvial aggradation continued in the Yangshao period (7.0–5.0 ka B.P.), they moved to a higher place, away from the rivers in the southwest, and flourished on high alluvial grounds. When a secondary terrace formed after the Longshan period (5.0–4.0 ka B.P.), people moved eastward again to build an early city on the T2 terraces and T3 terraces of the Ying River. When the water levels rose toward the terrace surfaces, they began to build moats and practiced mixed millet–rice farming. During the Eastern Zhou Dynasty (770–4256 B.C.), when the river started to down cut on a large scale, humans responded by building settlements on the lower and flat plains in the east.