UC Berkeley

This dissertation clarifies the nature of the relationship between a small group of ironworkers and their forest landscape in the fifth and sixth centuries on the Osaka Plain, and in so doing builds a model for investigating the relationship between craft production and landscape change more broadly.

Scholars have long pointed to metallurgical activities as factors in environmental transformations, but these studies have focused on smelting and refining activites, while disregarding smaller scale activities like smithing. Ogata, a large-scale ironworking site of the Middle and Late Kofun Periods located in Kashiwara City, Osaka Prefecture, Japan, has been excavated sporadically since the early 1980s, and the accumulated finds and data offer insight into questions of the reciprocal and knowledgeable influences between ironworkers and their local forest landscape.

This dissertation approaches this issue through reconstructing chaînes opératoires of ironworking, and extending them to encompass fuel procurement activities on the landscape. The knowledge involved in each step in a chaîne opératoire provides a way to investigate not only the choices that actors make, but also the motivation behind them. However, this is only possible with detailed knowledge of the craft as well as the landscape. In addition to the material characteristics and natural processes of the landscape, an appropriate understanding of the general nature of relationships between human activities and landscape transformation. This project adopted the research program of historical ecology as a lens through which to view the empirical evidence of landscape transformation and ironworking activities.

To facilitate reconstructing useful and accurate ironworking chaînes opératoires, this dissertation reviews the physical behavior and characteristics of iron and its alloys, along with charcoal fuel and the fundamentals of premodern ironworking technologies and techniques. It further examines the specific ironworking technologies known from the Kofun Period in the Japanese Archipelago. A close review of paleoclimatic data for the Japanese Archipelago as well as pollen data from other archaeological sites near Ogata establishes that the Osaka Plain in the Kofun Period was climatically much like the twentieth century, and that the area near Ogata was heterogeneously forested by lucidophyllous taxa with some elements of warm temperate deciduous forest as a result of disturbance by human activity. A review of Japanese lucidophyllous forest disturbance and regeneration dynamics and conservative estimates for rates of charcoal fuel in forge operations is used to estimate sustainable levels of wood harvesting for charcoal production. Next, the results of the main archaeological excavations at Ogata are introduced with an emphasis on artifacts and features related to ironworking.

With the these technological, archaeological, and environmental contexts established, analysis of twenty forge slags from four depositional contexts of the 1984-1 excavation is conducted. Since removing artifacts from Japan is difficult, these slags were prepared as petrographic specimens for reflected light microscopy and initially examined photographed by Suzuki Mizuho through Nippon Steel Technology Co., Ltd. Taxon identification and radiocarbon dating of charcoal fragments extracted from these slags was also conducted. Charcoal identification was conducted by Paleo Labo Co., Ltd, and AMS radiocarbon dating by Beta Analytic, Inc. Four additional pieces of charcoal and a charred peach pit from a possible charcoal kiln feature uncovered in the same excavation were also radiocarbon dated by Beta Analytic, Inc. The internal macrostructure of the forge slags was analyzed using a method pioneered by Vincent Serneels, Sébastien Perret, and Raphaëlle Soulignac allowing for the estimation of the forge slags’ formation process. This analysis was supplemented by reflected light microscopy of the slags.

Results of these analyses supported earlier hypotheses about ironworking at Ogata, concerning hardwoods as the preferred fuel, the use of at least some steel as working stock, and forge refining as one of the ironworking processes performed there. New results include the confirmation metallic copper in slags, indicating that copper was worked in some capacity at Ogata.

These analyses also revealed that the age of trees used for charcoal production increased significantly over time. This demonstrates that there were still some very old trees living nearby Ogata, but also that the need to harvest them arose, most likely due to decreased availability of younger wood from previous sources. At the same time, a new slag form emerged that suggests an increase in the speed of work or at least faster cooling upon completing work. Either possibility would entail somewhat reduced fuel expenditure compared to prior practices. These changes both indicate a concern with fuel availability for ironworkers, and reflect their prior insufficient management of forest resources, and a choice to economize with respect to fuel. This was not the only option available to ironworkers; they could have continued to use the same amount of fuel, further accelerating the apparent decrease in fuel availability over time, or negotiated for greater access at the expense of other fuel-users. However, it appears that found that introducing new ironworking techniques was the best way to manage the forest and the competing interests in its resources.

Beyond these results and establishing a chaîne opératoire approach as a viable model for investigating human-landscape relationships, this project also revealed several avenues for future research. Mori, the other major Kofun Period ironworking site in Osaka Prefecture, will be an excellent comparative case for Ogata using the same methodology and analytical techniques. At Ogata, additional research is necessary to clarify the role of copper and potentially copper-plated iron artifacts in the production and circulation of iron goods. Finally, this project revealed the need for additional experimental work on slag formation processes and postdepositional corrosion.