浙江大榭史前制盐遗址人工土台的堆土特征及来源分析*
Characteristics and origin of the earth from artificial mound of prehistoric Daxie salt-making site, Zhejiang Province

位于浙江省宁波市大榭岛的大榭遗址,是迄今所发现的中国最早的史前海盐业遗址,与一般遗址沉积地层不同,其主体区系人工堆筑土台。本研究在遗址发掘过程中,采集了泥质和砂质2种类型堆土、废弃陶器堆中的白色硬化物和盐灶坑表层白色硬化物,同时采集本岛自然堆积物,进行了粒度、无机元素地球化学和重矿物分析,以探讨堆土的原料构成、古人的制盐工艺及制盐活动对堆土地层产生的影响。研究结果显示: 来自盐灶遗迹附近的7个泥质堆土样品,其中5个具有陆相元素富集特征,但是后期受海水影响,另外2个显示滩涂盐泥特征;废弃陶器堆中的白色硬化物元素组成与盐泥相似,盐灶坑表层白色硬化物具高Ca、Sr、Ba含量,推测是烧煮卤水产生的沉淀物。砂质堆土的粒度和重矿物组成显示其属于河流冲积物,且具强烈的化学风化特征,推测其原始地层不仅限于全新统。该研究显示了钱山漾文化时期古人利用岛屿上的潮上带、山麓黄土、河流冲积物等原材料在滩涂营建土台,并在土台上利用“淋卤煎炼”工艺从事制盐活动。
Daxie site is the earliest prehistoric sea salt-making site discovered in China to date,and is located on the Daxie Island,Ningbo,Zhejiang Province. Artificial mounds constitute the major site. In this study,samples of muddy and sandy artificial earth from the Neolithic mound and samples of hard white material from the garbage and surface of salt-making stove during the archaeological excavation were collected. Samples representing the natural deposits on the island were also collected. Analysis including grain size,inorganic geochemistry and heavy mineral on these samples to explore the origin of the artificial earth and the influence of the salt-making activities were conducted. Results demonstrate that among the seven muddy earth samples collected from excavation units close to the salt-making stoves,five were of terrestrial origin,but also influenced by seawater. Origin of the other two samples were inferred to be the salty mud collected from tidal flat. The sample of white hard material from the garbage has similar elemental chemistry to the salty mud. The sample from the surface of salt-making stove is characterized by high content of Ca,Sr and Ba which is inferred to be the precipitation during boiling. Grain size and heavy mineral analyses of the sandy earth showed an alluvial origin with characteristics of strong chemical weathering,which imply that the original strata were beyond the Holocene. We imply that above results reflected prehistoric people's adaption and utilization of an island and its mud flat,which was using the supratidal, foothill deposits and alluvial sediments for constructing the artificial mound on the tidal flat , and making salt using the technique including leaching the salty mud and boiling the salt-enriched liquid