重庆中坝遗址早期文化层人类活动的多元素示踪

Multi-elementary tracing of human activities in the early cultural layers of the Zhongba Site in Chongqing

  • 摘要: 本文测试了重庆市忠县中坝遗址早期文化地层(640~1250 cm:新石器晚期、夏代和商代)的质量磁化率和常量元素含量,用元素含量中值比较法将文化层中的测定元素分为3类:① 富集型元素:Ba、C、Cu、Ca、Mg、Mn、P、Sr,② 流失型元素:Al、Cr、Fe、K、Na、V,③ 微变型元素:Co、Hg、Ni、Pb、Ti、Se,然后用主成分分析法遴选出对第一主成分有高贡献的元素。基于聚落功能区元素赋存对应的人类活动模式,探讨了3期文化地层中人类活动的变化特征:① 新石器文化层下段(950~1250 cm)的富集型元素Cu、Ba、Mg、Mn含量呈上升趋势,同时Cr、V、Al、K等元素加速流失,表明人类活动强度不断加深。新石器文化层上段(835~950 cm)的Cu、Ba、Sr含量逐渐走低,而Hg、Mg、Mn含量上升趋势明显,表明研究地层发生了从垃圾堆放区到住宅区的功能转化。② 夏代(740~835 cm)和商代文化层(640~740 cm)的红烧土和陶屑集聚量不断增加,表现为磁化率呈整体上升,流失型元素含量不断走低,人类活动强度持续增强。中坝文化地层的富集型元素、流失型元素以及Co、Fe、Mg、Mn等元素含量的变化不仅是人类活动干扰的结果,而且也是气候变化、地质过程和生物循环共同作用的结果, 特别是在降雨量快速变化的背景下。

     

    Abstract: The mass magnetic susceptibility and multiple elements in the early cultural strata (640~1250 cm, covering three cultural phases: late Neolithic period, Xia and Shang dynasties) in the Zhongba Site in Chongqing were tested, and the measured major elements in the late Neolithic and Xia-Shang cultural strata were classified into three types by element content median comparison and principal component analysis (PCA): (1) enriched elements: Ba, C, Cu, Ca, Mg, Mn, P, Sr; (2) depleted elements: Al, Cr, Fe, K, Na, V; and (3) slightly-changed elements: Co, Hg, Ni, Pb, Ti, Se. Based on the patterns of human activities corresponding to the characteristics of enriched or depleted elements, the variation characteristics of human activities in the three cultural phases were discussed. The lower Neolithic layer (950~1250 cm) presents increment in contents of Cu, Ba, Mg and Mn, and the accelerated losses of Cr, V, Al and K, indicating the intensification of human activities. The upper Neolithic layer (835~950 cm) shows a gradual decrease of Cu, Ba and Sr, and obvious increase of Hg, Mg and Mn, indicating that the Zhongba Site had changed from waste dumping to residential living in function. The Xia Dynasty (740~835 cm) and Shang Dynasty (640~740 cm) culture layers contain increasingly accumulated burnt-clay particles and ceramic sherds, and pose an overall increase in magnetic susceptibility and a continuous decrease in the content of depleted elements, reflecting the continuous increase in the intensity of human activities. We suggested that the changes in the contents of enriched elements, depleted elements, and other elements of Co, Fe, Mg, and Mn in the Zhongba Site are not only the result of human interference, but also the result of the combined effects of climate change and geo-biological cycles in specifically the context of rapid rainfall changes.

     

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