摘要： 四川省文物考古研究院2020年对掩埋坑周边区域展开了考古勘探,发现在靠近三星堆土台的南侧,存在有建造在二级阶地之上的壕沟,其古水流自西北流向东南沟通马牧河河曲段,壕沟沉积物主要形成时代推测为三星堆文化的第3期—第4期。通过对壕沟剖面样品进行薄片鉴定、扫描电镜观测和粒度分析研究,发现该壕沟主体由近源搬运的河流相沉积物组成,仅在个别地层富集陶片等遗物,壕沟以自然沉积为主,未发现大规模的人为倾填活动。生土及不同阶段的壕沟沉积物中岩屑等成分没有显著差异,表明自晚更新世以来,发源于龙门山构造带的湔江及其支流马牧河没有发生过明显的改道作用。壕沟至少经历了3次“挖沟—充填”的过程: 第1阶段沉积物主要为黏土及粉砂,水动力较弱,沉积环境比较稳定,古人活动频繁; 第2阶段沉积物主要为中粗砂,水动力较强,此时可能洪水频发,可见沟岸被明显切割并有大面积分布的越岸砂质沉积; 第3阶段沉积物水动力波动显著,后期逐渐稳定,古人重新回到壕沟区域。壕沟形态存在有多阶段人为修筑的痕迹,体现了古人对气候变化及自然作用的应对能力。

关键词: 三星堆遗址, 壕沟沉积物, 人类活动, 古洪水事件

Abstract: In 2020,the Sichuan Provincial Institute of Cultural Relics and Archaeology carried out archaeological exploration in the surrounding area of the burial pits. On the southern side of the Sanxingdui platform,there are trenches built on the second terrace. Paleocurrent flows from the northwest to the southeast to connect the Mamu River meandering section. The main age of trench sediments is speculated to be the third and fourth stages of the Sanxingdui culture. Through thin-section identification,scanning electron microscopy observation,and particle size analysis of the trench profile samples,it was found that the main part of the trench was composed of near-source fluvial sediments,and only pottery pieces and other relics were enriched in individual strata. The trench was dominated by natural deposition,and no large-scale anthropogenic dumping activities were found. There is no significant difference in the composition of rock debris and other components in the raw soil and trench sediments of different stages,indicating that the Jianjiang River originating in the Longmenshan tectonic belt and its tributary Mamu River have not undergone significant diversion since the late Pleistocene. The trenches experienced at least three ‘trenching-filling' processes. In the first stage,the sediments are mainly clay and silt,with weak hydrodynamic force,a stable sedimentary environment,and frequent activities of the ancients. The sediments in the second stage are mainly medium to coarse-grained sand with strong hydrodynamic force and there may be frequent floods at this time. It can be seen that the ditch banks are cut and a large area of sandy sediment is distributed across the banks. In the third stage,the hydrodynamic fluctuation of sediments was obvious and gradually stabilized in the later stage. The ancients returned to the trench area. There are traces of multi-stage man-made construction in the form of trenches,reflecting the ancients' ability to cope with climate change and natural effects.

Key words: Sanxingdui site, trench sediments, human activities, ancient flood events

中图分类号: 

• P534.63