Climatic shifts, geomorphic change, ancient routes of migration and adaption in southwestern China: Site formation processes at Luojiaba, Sichuan Province

Archaeologists frequentlyinvoke climate change as a driving cause for ancientexpansions of human populations, but geomorphic changes can also play an importantrole in opening or closing routes of migration. In China, archaeological evidencedemonstrates that valleys in the Jialing River's watershed were important routes forthe movement of Neolithic populations from the catchments of the Yellow River to theYangtze River. Here, we examine how fluvial geomorphological regime shifts may havealso influenced the migration pathways and adaptive strategies of Neolithic people intothe Sichuan Basin by using a combination of sedimentological and palynological analysisat Luojiaba, an archaeological site located onone of the eastern tributaries of the JialingRiver. The results show that people settled on seasonally stable landforms, including theZhonghe River floodplain at Luojiaba (5300–4800 cal. B.P.). They carried out fishing andhunting activities on the front edge of the floodplain close to the river channel and builtdwelling features on the higher ground at the back edge of the floodplain, which was notaffected by seasonal floods. We hypothesize that during the Holocene Climatic Optimumbefore 5500 cal. B.P., high water levels as well as severe surface erosion caused by astrong East Asian Summer Monsoon (EASM) blocked pathways into the upper reaches ofthe Jialing River watershed. Only after a series of cold, dry climate events driven by adecrease in EASM intensity ca. 5500–5000 cal. B.P. did water levels recede significantly.This allowed alluvial aggradation to occur, which created floodplains and terraces alongthe valley that may have opened a new route for the migration into the Sichuan Basin.Our results reveal the human–environment dynamics surrounding Luojiaba in the uplandsof southwestern China and highlight the impact of coupled climatic‐geomorphic regimeshifts on human settlement and subsistence strategies, across both space and time.KEYWORDS5500–5000 cal. B.P. climate event, fluvial geomorphology, geoarchaeology, Holocene,Jialing River, reverse adaptationGeoarchaeology. 2022;1–20.wileyonlinelibrary.com/journal/gea© 2022 Wiley Periodicals LLC.|1