泥河湾盆地火山角砾岩原料的热处理实验

Heat treatment experiments on the volcanic breccia materials from the Nihewan Basin

泥河湾盆地内发现了众多以精致楔形细石核为特色的细石器遗址。在以往的研究中,研究者对此类石制品组合进行了技术、类型等方面的研究,但其石料来源、石料是否经过热处理等问题仍未得到妥善解决。本文开展了盆地内旧石器时代晚期晚段常用原料火山角砾岩的调查和热处理实验研究。研究表明,泥河湾盆地六棱山基岩中的火山角砾岩,直接使用时,难以满足楔形细石核压制剥片对原料品质的要求;经过600°C的热处理后,其抗力性降低、延展性提高,剥片性能显著提高,可很好地进行楔形细石核的系统压制剥片。基于实验观察,同时借鉴其他学者的研究成果,本文对下卜庄遗址的相关材料进行了初步分析,发现了石料热处理行为的线索。对泥河湾盆地旧石器时代晚期遗址开展系统的石料热处理研究,有望揭示盆地内古人类对石料热处理的复杂行为。

Abundance of exquisite wedge-shaped microblade cores have been found at many microlithic sites in the Nihewan Basin.Through reconstructed reduction sequences of microblade technology,relationships between microblades and areas,microblade function and knowledge of lithic technology,researchers have a good understanding of human behavior,subsistence and adaptation in the Basin.However,there are still some questions such as raw material use.Bifaces and microblade cores are made of high-quality volcano breccia,showing smooth fracture faces and a greasy luster,whereas natural rocks lack these features,and the fracture patterns are rough and dull.This paradox is unexplained and some researchers suggest that heat treatment was applied to improve the quality of volcano breccia,but it has not been confirmed.By binding heat treatment experiments with flaking experiments,we have gained some important knowledge about the heat treatment of volcano breccia in the Nihewan Basin.When the volcano breccia is heated up to≥600°C,its resistance weakens,ductility is enhanced,flaking performance is improved significantly to make sophisticated bifaces and microblade cores,which is impossible with natural breccia.But not all volcano breccias show a greasy luster or color change,and this observation is the same with previous researchers.There is no doubt that flaking performance is the main transformation with the fracture of heated volcano breccia smoother.Before heating,however,volcano breccia’s fracture is rough.So heat-treated lithics retain several scars that are removed,but after heating there are two type of scars,rough and smooth.Heat treatment also induces conchoidal fractures,which can serve as valid evidence for the use of heat in this raw material.These characteristics are observed on some microblade cores and other lithics from the Xiabuzhuang site.We suggest that heat treatment is,indeed,used in the Upper Paleolithic in the Nihewan Basin,and it increases the diversity of human raw material selection and adaptability of use.