Archaeogeological implication of lithic artifacts from the Unjeonri Bronze Age site, Cheonan, Republic of Korea

The Bronze Age lithic artifacts from the Unjeonri sites in the Republic of Korea were studied on the basis of petrological, geochemical and archaeogeological interpretations. The use and rock names of the artifacts are a stone-grinding pestle (medium-grained two-mica granite), two stone-grinding plates (fine-grained two-mica granite and fine-grained quartz diorite), two stone axes (coarse-grained syenitic rock and graphitic schist), an unknown use artifact (biotite gneiss) and a stone knife (black slate). Values of magnetic susceptibility (MS) of the lithic artifacts are mainly less than 0.5 (10−3 SI unit); however, the syenitic rock (stone axes) ranges from 2.0 to 2.7. In the rocks around the relic sites, the MS values discovered were lower than 0.5. However, the syenitic rock stone axe, the graphitic schist stone axe, and the black slate stone knife showed different values from some of the measured rocks of an outcrop. Various kinds of rocks observed around the Unjeonri sites along the stream could be used for the stone-grinding pestle, the stone-grinding plate, and one of the stone axes. Each artifact was coupled with raw material samples rocks, and analyzed geochemically. The geochemical pattern of both lithic artifacts and sampled rock were identical when normalization was used to identify the behavior, enrichment, compatibility, and incompatibility of the elements. Therefore, it is possible that the source rocks of the interpreted lithic artifacts are distributed in the vicinity of the relic sites with the exception of one a stone axe (graphitic schist), the stone knife (black slate), and a stone arrowhead (gray shale); they did not conform to typical occurrences within a 10 km radius distribution area of the site. Consequently, in the Unjeonri sites, the artifacts suggest that the two types of materials coexist as domestic and foreign lithic artifacts. Using raw materials in situ, the domestic rock types (grinding pestle, plate, and axe) are self-sufficient. The foreign rock types (knife, arrowhead, and axe) are presumed to have been introduced from a different area. The foreign types should be examined for various introduction possibilities such as tribal migration, diffusion, plundering, or trade.