重庆中坝遗址剖面磁化率异常 与人类活动的关系

结合古器物推定及¹⁴C 测定年代、人类遗存遗迹和堆积物自然属性特征, 重庆中坝考 古遗址多剖面地层高分辨率采样的质量磁化率(SI) 综合对比研究表明: 磁化率分布表现异常, 在很大程度上已掩盖了气候变化、成土作用等因素对地层磁化率分布的贡献, 反映遗址堆积物曾受到人类长期异常强烈的改造。堆积物来源主要以文化器物碎片、人为带入的自然碎屑物和频繁的洪水沉积物为主。碎陶片集中(尤其红陶) 的文化层表现为高磁化率值, 其中多次异常高值的出现可能与此时高强度用火、大规模燃烧等事件致使土层磁性矿物增加有关; 而" 洪水扰动层" 则表现为低磁化率值。进一步分析曲线还可发现, 中坝地区新石器末至唐代是人类活动的活跃期, 宋以后人类活动有逐渐减弱的趋势, 其中新石器时代末、夏商中期、西周早中期、春秋时期、战国中晚期、六朝时期及唐代为活跃期中的旺盛阶段。新石器晚期、夏商早期、西周早期、春秋晚期、战国早期、宋代、明清和现代地层中洪水扰动明显, 推断 为洪水频发时代或此间曾出现过特大洪水。

Relationship between Abnormal Phenomena of Magnetic Susceptibility Curves of Profiles and Human Activities at Zhongba Site in Chongqing

Based upon the ages inferred by cultural relicts, AMS 14C dating, phenomena of human activitices and characteristics of magnetic susceptibility (SI) curves of profiles at Zhongba Site in Chongqing, we find that the contribution of climate change and soil formation to the distribution of magnetic susceptibility values in stratum is concealed by the impact of the abnormally strong human activitices for a long time. The results of analysis indicate that the sources of accumulation at Zhongba Site include mainly enormous ceramics fragments, natural scrap materials from human activities and flood deposits. The cultural layers gathered with a large number of ceramics fragments (red pottery particularly) show high magnetic susceptibility values, among them, the especially abnormal high values may be concerned with the increase of the magnetic materials caused by mankind's using the fire and burning on a large-scale at that time; on the other hand, the "flood disturbed layers" usaully show low magnetic susceptibility values. Based on further analyses of the magnetic susceptibility curves, we can still find that the active epoches of human activities was from the final stage of the Neolithic Age to the Tang Dynasty, and human activities began to tend to be weakening after the Song Dynasty. During the active epoch, the final stage of the Neolithic Age, the middle period of the Xia and Shang dynasties, the early and middle periods of Western Zhou Dynasty, Spring and Autumn Period, middle and late stages of the Warring States, the middle period of the Six Dynasties and Tang Dynasty were in the periods of great prosperity. However, there are obvious flood disturbed deposits included in the layers of the late stage of the Neolithic Age, the early period of the Xia and Shang dynasties, the early period of Western Zhou Dynasty, the late period of Spring and Autumn Period, the early period of the Warring States, Song Dynasty, Ming and Qing dynasties and modern period, which can be inferred to be the ages of the occurrence of severe floods.