GEOCHEMISTRY OF STONE TOOL SOURCES ON HAWAII ISLAND AS DETERMINED BY EDXRF

Geochemical source characterization for stone tool artifacts in the Hawaiian archipelago using non-destructive EDXRF is complicated by the presence of ubiquitous basalt flows on the islands. Unlike obsidian characterization, which often involves individual source area volcanoes which may have very different compositions, colors, and textures, Hawaii stone tools are generally made from black, fine-grained, dense basalt. Fortunately volcanoes in the Hawaiian hot spot chain evolve geochemically through a predictable pattern as they move away from the hotspot. Hawaii Island benefits from having volcanoes in several different phases of volcano evolution. This provides the basis for significant discrimination of material in an otherwise relatively homogenous source. We recognize and describe the geochemical signature of three significant source areas on Hawaii Island (Kilauea Summit Lithic Block Quarry, Pololu Valley-Kohala Volcano, and Mauna Kea Adze Quarry Complex), and their utility in deciphering domestic lithic assemblages. While the overall geochemistry of Hawaii is well known through many different methods of analysis, specific information on discriminating elements from archaeologically significant sites is not. We rely heavily on trace elements (Rb, Sr, Y, Zr, Nb) to discriminate sources due to higher precision with our instrument and greater % variation within Hawaiian rocks. Principal component analysis of rocks from the Pololu Quarry and the Mauna Kea Adze Quarry show significant differences between the measured range of geochemical compositions within the quarry and geographically proximate lava flows. Lithic blocks with similar geochemical signatures near the summit of Kilauea were preferentially selected for the manufacture of stone tools from the site.