浙江余杭跳头遗址晚商-西周早期铸铜活动的沉积地层记录

THE SEDIMENTARY STRATIGRAPHIC RECORDS OF COPPER CASTING ACTIVITIES DURING THE LATE SHANG-EARLY WESTERN ZHOU PERIODS AT THE TIAOTOU SITE IN YUHANG,ZHEJIANG PROVINCE

青铜器的使用对人类社会意义重大。作为生产青铜器的场所,铸铜作坊在铸造过程中会在当时环境中遗留下许多痕迹。然而,目前还较少有关于铸铜活动沉积地层记录的研究报道。本研究在浙江余杭跳头铸铜遗址(30°15′00″N,119°53′39″E)选取T1614S(总长400 cm)和T1510S(总长255 cm)两个剖面的沉积物样品,结合遗址附近的现代河道样品,运用AMS^(14)C、粒度、磁化率、有机地球化学和重金属元素分析,试图探究埋藏古河道的演变过程,探讨古代社会铸铜活动对环境的影响。研究结果发现:T1614S剖面的埋藏古河道在1045~830 BC(晚商-西周早期)期间,平均粒径(Mz)相较前一个阶段的13.0μm增大至23.5μm,分选变差,砂组分(4.7%~19.0%)增大,但整体上水动力较弱,推测是先越人为铸铜开挖的蓄水池或水沟;830 BC(西周晚期)之后,水动力增强,随后动力环境与现代铜山溪河道相似;85 A.D.(东汉)后,河道中堆积洪水地层;最后古河道消失,成为湖泊环境。在1045 BC时,TOC、C/N和δ^(13)C等有机地球化学指标也同步发生突变,阶段平均值分别从0.21%、3.39和-21.05‰变为6.70%、14.38和-27.74‰,同时伴随Cu、Zn元素含量分别从21.90 ppm和88.62 ppm突然增加到33.60 ppm和136.63 ppm。上述结果表明,晚商时期先越人在跳头遗址开挖古河道、使用大量燃料,并开始铸铜活动;Pb元素含量稍晚也从6.46 ppm突增至23.40 ppm,可能反映了先越人铸铜技术的进步;T1510S剖面晚商至西周文化层的χ_(fd)%达到6.82%~8.13%,反映了铸铜作坊区的用火行为,但是其重金属元素含量在西周文化层才持续增高,反映铸铜遗址不同功能区的地层记录差异。值得注意的是,跳头遗址铸铜活动结束后。两个剖面重金属元素含量持续呈现高值,反映遗址上游的铜山溪流域在历史时期也许一直存在采矿甚至冶炼活动,同时余杭地处钦杭成矿带,因此本研究推测跳头遗址商周时期的铜矿可能也来源于铜山溪流域。对比自然环境和社会背景,推测跳头遗址铸铜活动的兴衰主要与社会因素有关。

The utilization of bronze ware holds significant importance in human society.As a place for the production of bronze ware,the site of workshop preserves many traces of copper casting activities in the environment.However,there are few research reports focusing on the sedimentary stratigraphic records of copper casting activities to date.In this study,two profiles T1614S(400 cm) and T1510S(255 cm) were selected from the Tiaotou copper casting site in Yuhang,Zhejiang Province( 30°15′00″N,119°53′39″E),together with collection of channel sediments from the present-day river near the site.As for research methods,74 samples from profile T1614S,20samples from profile T1510S and 12 samples from the present-day river channel were analyzed for grain size;20samples from profile T1510S were tested for magnetic susceptibility and 74 samples from profile T1614S were analyzed for organic geochemistry(including total carbon(TC),total organic carbon(TOC),total nitrogen(TN)and stable isotope of organic carbon(δ13C));22 samples from profile T1614S and 20 samples from profile T1510S were analyzed for heavy metals Cu,Zn,and Pb.The purpose of this study is to explore the evolutional process of buried paleo-river channel and the influence of ancient society's copper casting activities on the environment.The results show that the Mzof buried paleo-river channel in profile T1614S increased from 13.0 μm to 23.5 μm during1045 ~830 B.C.(late% Shang-early Western Zhou),compared with the previous stage,the sorting declined and the sand component(4.7~19.0%)increased,indicating weak water currents.So the channel is presumed to be the reservoir or ditch excavated by Pre-Yue people for copper casting.The hydrodynamic force increased after 830 BC(late Western Zhou),and then reached a similar level to the modern Tongshan River channel.The flood deposits accumulated in the river channel after 85 A.D.(Eastern Han),and the paleo-river channel disappeared and finally became a lacustrine environment.At 1045 B.C.,the organic geochemical indexes such as TOC,C/N andδ13C also changed from 0.21%,3.39 and-21.05‰to 6.7%,14.38 and-27.74‰,respectively,while contents of Cu and Zn suddenly increased from 21.90 ppm and 88.62 ppm to 33.60 ppm and 136.63 ppm contemporaneously.These changes show that the Pre-Yue people artificially transformed the environment at the Tiaotou site,including the digging of waterway,utilization of large amount of fuels and the copper casting in the late Shang period.The content of Pb increased sharply from 6.46 ppm to 23.40 ppm later,which may reflect the progress of copper casting technology of Pre-Yue people.The χ Shang to the West Zhou,reflectinfd%of profile T1510S reached 6.82%~8.13%in the cultural layer from the lateg the behavior of fire in the workshop area,while the content of heavy metals continuously increased in the cultural layer of the West Zhou,indicating the variation of stratigraphic records in different functional areas of the copper casting site.It is worth noting that after the end of the copper casting activities at the Tiaotou site,the heavy metal contents in the two profiles continued to show high values,which may reflect that mining and even smelting activities had always existed in the Tongshanxi basin upstream of the site throughout the historical period.Meanwhile,Yuhang area is located in Qin-Hang metallogenic belt.Therefore,this paper speculates that the copper source of the Tiaotou site may also come from the Tongshanxi catchment in the Shang and Zhou Dynasties.Comparing the natural environment and social background,it is speculated that the rise and decline of copper casting activities at Tiaotou site is mainly related to the social factors.