Abstract:

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.

Key words: Upper Paleolithic, Nihewan Basin, Heat Treatment, Microbalde Technology, Experimental Archeology