Archaeology : The Historical Context Buried Beneath the Kofun (Mounded Tombs)


Okayama University Graduate School of Humanities and Social Sciences Jun Mitsumoto, Associate Professor


Okayama prefecture is a region where, even by national standards, the number of kofun (mounded tomb) is considered numerous. There are various clues buried within the kofun including not only information concerning the people buried there, but also details of the historical context, networks, and so forth. Associate Professor Mitsumoto and his group are conducting detailed research on the kofun in the prefecture by conducting repeat excavation surveys with three-dimensional laser scanning and hand surveys.

What kind of surveys do you conduct, Professor Mitsumoto?

In order to investigate the kofun, first, it is imperative to know the exact shape of the kofun. The research then progresses into questions such as the meaning of the kofun’s shape, and precisely when during the Kofun Period it was built. In my group, we have carried out surveys using lasers to take three-dimensional measurements and then proceeded to conduct excavation by hand. The benefit of three-dimensional measurements is that it is more precise than a two-dimensional contour diagram; terraces (a series of stepped, flat surfaces) and so on can be identified, even if they are hard to make out in a contour diagram. Every year, a survey is conducted at the Tsukura Kofun (early 4th century), which has been under investigation by the Okayama University Archaeological Research Laboratory since 2013; this year, we conducted our fourth survey. Each survey is conducted by about 10 to 20 people, including students, and lasts for several weeks to a month. In the case of the kofun, it is necessary to record precise data step by step; data such as the color and depth of the soil, the type of stone, the sedimentary state, and so on. Furthermore, we work throughout the year, as we have to compile reports after the excavation survey is over.

What kind of things can you understand from looking at the tomb?

Towards the end of the Yayoi Period, in addition to tombs where everyone was buried, tombs began to appear where only specific individuals could be buried. In other words, when you look at a tomb, you can partially view the microcosm of society during that time. By looking at how people were buried, or what kind of stone was used, etc., we can understand aspects of social status and networks from the times in which they lived.

To that end, what have you learned from conducting surveys at the Tsukura Kofun?

The tateanashiki sekishitsu (pit-style stone chamber, the place where the body is entombed) of the Tsukura Kofun is made from andesite from Kagawa prefecture. As noted in previous studies, andesite was prevalent in Kibi during the early part of the Kofun Period and was used in part for the influential Kibi Kofun. However, the quantity is a mystery. The Tsukura Kofun is a relatively large mound of 38.5 meters in length, but the amount of stone used is comparable to that of a gigantic burial tomb in the 140-meter class. It is said that the larger the kofun, the higher the status, but what does the amount of stone demonstrate? Why would a large amount of andesite be used in a kofun that is not that big, such as the Tsukura Kofun? Answers cannot be found without further excavation, but at that time the ocean was quite close to the southern part of the Tsukura Kofun; perhaps the individual was involved in maritime trade and had a network that extended across the ocean. Perhaps it was a person involved in the supply of tateanashiki sekishitsu building stones from Sanuki to Kibi. One can imagine a number of possibilities.

In March of this year, a bronze mirror discovered in the Tsukura Kofun attracted attention.

Yes. Within one of two pit-style stone chambers, near the head of the western stone chamber, a bronze mirror was discovered, which appears to be a Japanese mirror produced in the Japanese archipelago. It is an important clue to discovering the precise period of the tomb and details regarding the buried individual. It may be a kind of mirror known as a daryukyo, but the details of the mirror, including the patterns and type of mirror, will be examined further after it has been cleaned. As a result of the most recent excavation, we have also been able to identify the mirror’s exact location within the stone chamber. In the third year of excavation at the Tsukura Kofun, a haji ware jar (a low fired brown pottery) was discovered, and in the fourth year, this year, a bronze mirror was excavated. In the first two years, almost nothing was excavated, and it was difficult to find any clues, so when I found the mirror, I was very excited.

Please tell us about your future projects.

When compared to the kofun, mounded tombs of the Yayoi Period do not have much of a uniform shape; a uniform method of burial finally began to appear in the Kofun Period, with defined shapes, burial patterns, and so on. The shift from the Yayoi Period to the Kofun Period is considered a significant turning point, from an era that had a number of different shapes to an era of uniform shapes. Thus far, Okayama University has contributed to the solution of the process of the establishment of kofun as mentioned above. With the latest measurement technology, I hope to clarify the mechanism of change between the periods based on the excavation results of the Tsukura Kofun.

Finally, please give a message to students who are interested in pursuing Archaeology.

Although excavation is thought of as slow-going work, it is work that must be done responsibly. Once you have dug something up, it cannot be put back. Furthermore, writing the reports is a challenging task that involves carefully noting everything in great detail because later on it will be used as your basic data. It will not be a prestigious researcher but the students themselves, who will be excavating the site, well versed in this kofun. I want them to enjoy the sensation of excavating for themselves and making new discoveries.

Brief biography

Jun Mitsumoto Jun Mitsumoto was born in 1975. He graduated from the Okayama University Faculty of Letters. He completed his Ph.D. (literature) with the Okayama University Graduate School of Humanities and Social Sciences. After working as an assistant/assistant professor at the Okayama University Archaeological Research Center, he began his current position in October 2012. He specializes in archaeology and museum studies.


Excavated bronze mirror

Professor Mitsumoto