重庆忠县甘蔗丘遗址商周时期以来环境考古研究

ENVIRONMENTAL ARCHAEOLOGY OF GANZHE HILL SITE IN ZHONG COUNTY OF CHONGQING

通过对重庆忠县甘蔗丘遗址自商周时期以来的215cm厚的文化堆积层进行孢粉、炭屑和磁化率指标的综合研究。结果表明,商周时期出土器物丰富,磁化率值和炭屑浓度整体较高,但孢粉浓度很低,表明该地点处于一级阶地上,先人在此生活不仅用水方便,且因当时气候偏干凉,较少受到极端洪水灾害威胁,较高的炭屑表明了古人用火频繁。到唐宋时期中期,出土器物明显减少,孢粉浓度增大,且属种增多,尤其是喜湿植物孢粉浓度明显增大,可能表明该时期环境较为潮湿,居住地有可能受到洪水破坏,农业活动在遗址处开始发展,其炭屑浓度和磁化率值减小的特征也说明人类居住地迁出和土地性质已开始以初级农业活动为主。唐宋后期气候更为暖湿,区域降雨量增大,由于遗址区位于长江干流一级阶地上,易受洪水灾害的威胁,先民在该区的活动进一步减少。明清时期早期,孢粉浓度虽然变化不大,但水稻型禾本科花粉浓度大幅度增加,次生性的松属也相应较高,显示出人类农业活动增强,遗址地可能逐渐演变为农田;到了明清后期,炭屑浓度和磁化率值又逐渐增大并出现峰值,反映遗址区开始受到近代农业活动的强烈影响。

Combined analysis of palynomorphs,charcoal, and magnetic susceptibility of the Ganzhe hill site in Zhong County of Chongqing, shows that during the Shang and Zhou Dynasities, when tons of cultural relics were unearthed and the magnetic susceptibility values and overall concentration of charcoal were high, the pollen and spore concentration was low. In the relatively dry and cold climate of that time, ancestors settled down on a river terrace, therefore avoiding extreme flood threat. In the succeeding mid Tang and Song Dynasties, the number of unearthed cultural relics decreased sharply and charcoal and magnetic susceptibility values also dropped, whilst palynomorph species and concentration, especially of those plants which tended to grow in humid conditions, increased significantly indicating that the environment was humid in this period and that the site had tended to be damaged by flood and then agricultural activities had began. The characteristics of magnetic suscep- tibility and of the charcoal illustrate that the settlements had moved out and that agricultural activities had begun again. In the warm and humid climate of the late Tang and Song Dynasties, regional precipitation increased and the area was prone to flood as it was located on the Yangtze River level terraces, which, as a result, reduced human activities still further. In early Ming and Qing Dynasties, palynomorph concentration changed little, whilst, secondary Pinus pollen concentration increased considerably, indicating enhanced human agricultural activities, and the site gradually evolved into rice farmland. In the late Ming and Qing Dynasties, the emergence of another peak concentration of charcoal and gradual increase in magnetic susceptibility values, indicate that the site area began to be even more strongly influenced by human activities.