Fluvial downcutting and its influence on human settlement in the middle reaches of the Lancang River

Abstract

The Lancang River valleys have been inhabited by humans since the Neolithic period, during which the fluvial landscape has experienced rapid changes due to intense river incision. However, the ways in which ancient human activity and adaptation were shaped by these landscape transformations remain poorly understood. In this study, optically stimulated luminescence (OSL) and radiocarbon (¹⁴C) dating techniques were employed to determine the ages of fluvial landforms around the Jicha archaeological site in the middle reaches of the Lancang River. The results suggest that fill terraces T₁₋T₃ were deposited during the periods of ~5.0–2.7 ka, ~8.0 ka and ~ 54.5–30.0 ka, respectively. Human activity at the Jicha archaeological site occurred during the ~3.8–2.2 cal ka BP, overlapping with the deposition period of T₁ (i.e., ~5.0–2.7 ka). Following the downcutting of T₁ after 2.7 ka, the river valley floor likely became less suitable for rice cultivation, leading to the probable abandonment of the Jicha archaeological site around ~2.2 cal ka BP.