史前城址作为早期城市演化的关键组成部分,与气候、地貌以及水文等区域环境因素密切相关.然而,目前的研究在考虑史前城址相关的区域环境因素方面存在不足.本文基于长江中游地区典型遗址走马岭古城的上津湖钻孔沉积记录和完整的年代框架,结合元素地球化学等气候代用指标分析,重建了中晚全新世走马岭古城遗址的区域沉积环境演变过程,并探讨了其与人类活动的关系.研究发现:①6.4-5.3 kaBP期间,CIA、Rb/Sr、Mn/Ti值总体较高,Be、Saf值呈相反趋势,指示气候较温暖湿润.此时屈家岭下层文化时期的先民在走马岭修建城址.②5.3-4.7 kaBP期间,CIA、Rb/Sr、Mn/Ti值上升至峰值,气候暖湿.稻作农业得到发展,屈家岭文化在走马岭古城达到鼎盛.其中4.7-4.6 ka BP期间,粒度参数异常上升,指示古城发生强降水导致的洪水事件.③4.7-4.2 kaBP期间,气候转向凉干,古城的石家河文化逐渐衰落.④4.2-2.4 ka BP期间,CIA、Rb/Sr、Mn/Ti值降至最低,气候变凉干,古城在3.9 ka BP被废弃.⑤2.4-0.3 kaBP期间,CIA和Rb/Sr值回升,Saf和Be值下降,气候回暖.0.8 kaBP左右,上津湖形成.0.3-0.1 kaBP期间,CIA、Rb/Sr值大幅降低,Be和C/N值异常升高,指示在明清小冰期的鼎盛期,走马岭气候寒冷干旱.但是当时围垦等人类活动频繁,初级生产力高.走马岭古城的城内水源主要依赖东南侧的蛇子岭水体,雨季时打开西水门,洪水通过壕沟排入上津湖.旱季时关闭西水门,靠城外蛇子岭水体引水供城内用水.后期气候转向凉干时,水体枯竭导致走马岭古城的壕沟系统失去作用,古城被废弃.
Environmental change and human adaptation at Zoumaling city since mid-Holocene,midstream of the Yangtze River,China
Integral early urban evolution of prehistoric city sites are intimately related to regional environmental factors such as climate,geomorphology,and hydrology.However,current research is inadequate in considering the regional environmental factors associated with prehistoric city sites.This study utilizes the Shangjinhu Lake sedimentary record and a comprehensive chronological framework of the ancient city of Zoumaling,a typical site in the middle Yangtze River.By analyzing climatic proxies such as elemental geochemistry,it offers a reconstruction of the regional depositional environment of the Zoumaling site during the mid-late Holocene.Furthermore,it explores the connection between regional environment and human activities.The study indicates that:(1)During 6.4-5.3 ka BP,the CIA,Rb/Sr,and Mn/Ti values were generally high,and the Be and Saf values showed an opposite trend,indicating a warmer and wetter climate.The ancestors of the lower Qujialing culture constructed the city of Zoumaling.(2)During 5.3-4.7 ka BP,the values of CIA,Rb/Sr,and Mn/Ti reached their peak,and the climate was warm and humid.Rice agriculture flourished and the Qujialing culture in Zomaling city reached its heyday.Specifically,between 4.7 and 4.6 ka BP,a significant rise in grain size parameters indicates that the ancient city was subjected to flood events due to intense precipitation.(3)During 4.7-4.2 ka BP,the climate became cooler and drier.Consequently,the Shijiahe culture within the Zomaling city began to decline gradually.(4)During 4.2-2.4 ka BP,the CIA,Rb/Sr,and Mn/Ti values fell to their lowest,indicating a shift to cooler and drier climate conditions,and the ancient city was abandoned around 3.9 ka BP.(5)During 2.4-0.3 ka BP,CIA and Rb/Sr values rebounded and Saf and Be values decreased,indicating a warming climate.Around 0.8 ka BP,the Shangjinhu Lake was formed.During 0.3-0.1 ka BP,the values of CIA and Rb/Sr decreased sharply,and Be and C/N values increased,indicating a cold and arid climate at Zomaling during the heyday of the Ming-Qing Little Ice Ages.The primary productivity was high due to frequent human activities like land reclamation.The Zomaling city primarily depended on the Sheziling waterbody for its water supply.During the rainy season,the west water gate was opened to release flood water into the Shangjinhu Lake via the trench.During the dry season,the west water gate was closed,and water was drawn from the external Sheziling waterbody to supply the city.In the later period,as the climate turned cooler and drier,the depletion of water bodies caused the moat system of the Zoumaling city to become ineffective,resulting in its abandonment.
Holocenemiddle Yangtze Riverenvironmental evolutioncity trenchancient city of Zoumaling
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