publ.: July 2007
Photos: MATSUGI Takehiko, NIIRO Izumi and Jane OKSBJERG
(Click on photos to enlarge)
A group of students from Okayama 岡山 University are currently in the final phase of an excavation season that took its start in the middle of February this year. They are excavating what is one of the most exciting sites for any archaeologist; an unlooted grave inside a burial mound. The excavation of Shōbuzako Kofun 勝負砂古墳 (Map 1), led by Associate Professor MATSUGI Takehiko 松木武彦 from Okayama University, is part of a larger project throwing light on the late 5th and early 6th century burial mounds of Kibi 吉備, the ancient name of the region included by the Okayama Plain facing the Inland Sea and today the home of Okayama City. Kibi can be identified as a political centre already in the Yayoi 弥生 period (800 BCE – CE 250) together with those of Kinai 畿内, Izumo 出雲 and northern Kyūshū 九州.
Shōbuzako is situated on a plain in the Mabi 真備 area near Kurashiki 倉敷 at the lower reaches of the
Oda 小田 River where this flows into the Takahashi 高梁 River (Map 2:3). It is built 600 m south of the
Oda River, 500 m west of the conspicuously well-situated Tenguyama Kofun 天狗山古墳 (Map 2:4), and only 200
m east of its nearest neighbouring mound, the Nima-Ōtsuka Kofun 仁万大塚古墳 (Map 2:2). Several other mounds,
individually and in clusters, are erected in the same area, the Nima section near the northern bank
of the river. Also on the northern side of the Oda River, a multitude of mounds were erected in the
Kofun period (CE 250 – 538), although here they are further away from the stream. The larger Takahashi
River, whose current changes its direction towards east in the vicinity of Shōbuzako and its neighbouring
mounds, separates the Mabi Plain from the Sōja 総社 Plain to its east, housing other mounds and mound
clusters, including the largest mounds in Kibi.
Map 1: General location of Shōbuzako Kofun in Okayama Prefecture and location of ancient Kibi
Map 2: Location of sites mentioned in the text. 1. Kuromiya-Ōtsuka site, 2. Nima-Ōtsuka Kofun,
3. Shōbuzako Kofun, 4. Tenguyama Kofun, 5. Misu-Tsukuriyama Kofun, 6. Kamo-Tsukuriyama Kofun.
The wide plain of Kibi houses numerous kofun mounds spread all over its lowland in a seemingly homogenous distribution; however, as we shall learn shortly, with very varied temporal concentrations in the different areas, which are demarcated by natural borders in the shape of a multitude of rivers that cross the plain on their way to the Inland Sea.
Kibi boasts two giant mounds from the early 5th century, Kamo-Tsukuriyama 加茂・造山 Kofun [fn. 1] (360 m in length) that is situated in the southern part of Sōja Plain (Map 2:6) and Misu-Tsukuriyama 三須・作山 Kofun (286 m) (Map 2:5), located to the west of the lower reaches of the Ashimori 足守 River. Both are keyhole shaped mounds (Jap. zenpō kōenfun 前方後円墳). However, in the second half of the century, during what is called the 'Yūryaku dynasty 雄略(朝)' [fn. 2] period, no large scale mounds of keyhole shape were constructed in the Kibi area. A few mounds were built in the landscape surrounding Kamo-Tsukuriyama, but these are of a diameter of less than 50 m. Also at the Suna 砂 River, where the keyhole shaped Ryōgūzan 両宮山 Kofun (190 m) had been erected in the middle of the 5th century, there was a decline in the building of large mounds in this phase (MATSUGI ed. 2001:26).
In contrast to this, the Mabi area at the Oda River at the outskirts of the Kibi region, an area whose role in terms of mound building had hitherto been extraordinarily modest, started construction, and even with mounds whose size surpassed those of the previously 'leading' areas. Thus, we here have Tenguyama which is strategically placed next to the junction of two rivers, and we have Nima-Ōtsuka which proved to be one of the earliest passage grave mounds in Kibi (NIIRO 2006). Both will be dealt with in detail below.
Almost no burial mounds had been built in the Mabi area since the square tumulus of Kuromiya-Ōtsuka 黒宮大塚 (Map 2:1) was constructed in the 2nd century. No Early Kofun – 3rd and 4th century – mounds exist in the area. 'Kings' who were sufficiently influential to order the construction of burial mounds for themselves or their predecessors thus seem to have been absent in the Mabi area until the latter half of the 5th century, when construction was initiated of mounds that were on average larger in size than those built in the areas that house the above mentioned giant mounds built earlier in the century.
The 'Yūryaku-dynasty project' carried out by the researchers at Okayama University and their students aims at answering the question of what the mound sequences in the Kibi region mean by surveying and excavating mounds constructed in Mabi and beyond from that phase and until the middle of the 6th century. The project [fn. 3] was initiated in 1998 by Professor NIIRO Izumi at Okayama University, who conducted the excavations at Nima-Ōtsuka Kofun (NIIRO 2005) from 2001 to 2004 and Associate Professor MATSUGI Takehiko who led the excavations at Tenguyama Kofun (MATSUGI ed. 2001) from 1998 to 2000. Now, investigations at Shōbuzako Kofun are drawing to a close.
The investigations carried out in the Nima section so far indicate that a powerful dynasty was founded in the previously insignificant Mabi area in the Yūryaku dynasty period, a dynasty that continued to build burial mounds also in the early 6th century, Late Kofun, when the practise had come to a complete stop in many areas within the Kibi region.
Tenguyama (Map 2:4) is a scallop shaped (Jap. hotategai-gata 帆立貝形) mound [fn. 4] that – placed as it is on the top of a small mountain 80 m above sea level – overlooks the place where the Oda River flows into the Takahashi River and commands a fine view of the alluvial plain formed by the Oda River, telling clearly of the role of this mound as the basic one of the plain (MATSUGI ed. 2001:2). The mound itself measures 60 m, but it is enclosed with an earthen dike that gives the feature a total length of 80 m. [fn. 5] At its south-western edge, the small Tenguyama-Nishi 天狗山西 mound, measuring 10 m in diameter, is attached.
Mirrors, horse gear and armour had already been unearthed during a pre-war excavation of the vertically
established stone chamber
in Tenguyama, when the researchers at Okayama University decided to make renewed investigations. The
burial chamber (Fig. 1) was rectangular and measured 3.9 × 1 m. The foundation stones of the walls built
by small boulders had been solidly buried, and the wooden coffin placed on the surface. Six large flat
capstones covered the chamber, giving it a height of 0.8 m.
Sherds from cylindrical haniwa 埴輪, some with flaring mouth and all with a diameter between 20 and 23 cm, were recovered from all over the mound. The base of 23 of these still stood at their original spots creating a row along one side of the round part and the adjoining constriction. [fn. 7] From the square part a large quantity of sherds from the same type of haniwa [fn. 8] were collected (MATSUGI ed. 2001:19).
Sue ware (Jap. sueki 須恵器) dating from the latter half of the 5th century was recovered from
different parts of the mound, but in particularly large quantities from the ceremonial platform.
The chamber, whose floor was located 5 m below the top of the mound, was entered using the route left
by the earlier excavators. During the excavation a dagger, two spears and a halberd of iron were recovered
as was horse gear and armour (MATSUGI ed. 2001:17, 25).
Several aspects of the Tenguyama mound bear evidence of close contact between the leaders in the area and those in the Korean Peninsula during the Yūryaku dynasty phase. The clay filling between the stones used to build the chamber and the fact that the chamber was placed in such great depth from the surface are phenomena that show the peninsular influence, and pieces among the recently excavated Sue ware proved to be imported from the south-western part of the Korean Peninsula (MATSUGI ed. 2001:26).
Nima-Ōtsuka (Map 2:2) is a representative of what happened in the Mabi area in the early 6th century, i.e. Late Kofun. As mentioned, after the Yūryaku dynasty period, the construction of regularly keyhole shaped mounds ceased and scallop shaped mounds were built instead, but Nima-Ōtsuka marks the revival of the keyhole shape (NIIRO 2005:29).
This mound that is situated 200 m west of Shōbuzako and close to the small Nimadani 仁万谷 River flowing
into the Oda River to its north-west was excavated from 2001 through 2004, and a multitude of beautiful
in situ finds were revealed during the investigations. What makes up one of the most lasting
impressions, however, was the fact that the mound was equipped not with a closed shaft hole chamber
but with a passage grave chamber (Fig. 2).
Nima-Ōtsuka measures 38 m and is thus somewhat smaller than the earlier Tenguyama. Sue ware recovered from the surface of the northern constriction prior to excavation had led the excavators to anticipate the ceremonial platform (NIIRO 2005:9). Here, the platform consisted in a natural hill that had been levelled down to fit the height of the lower of the two tiers making up the mound. The base of the top tier had a slightly smaller circumference than the top of the bottom tier, creating an all encircling terrace on which haniwa had been lined up.
The lower tier had been built after levelling down the mountain (NIIRO 2005:6, 16), and it included the stone chamber and the passage, at whose outer walls the earth could be observed to have been fitted carefully in between the stones. An isolated area was discovered of whitish burnt soil located near the top of the chamber containing a concentration of about 40 small and fragile sherds from the neck of a 6th century pot. Based on this find, it is assumed that a fire-involving ritual took place after the completion of the stone complex and the lowest tier. Nothing similar to this phenomenon was recovered anywhere else within the fill of the mound (NIIRO 2005:20). The pottery itself carried no traces of fire, but the general appearance of the find seems to reflect a phenomenon that could be observed inside the chamber involving charcoal. (This will be dealt with below).
The bases of 49 haniwa were still in situ extending along one side of the mound including
the inner line of the ceremonial platform (Fig. 3). On top of the platform figuratively shaped haniwa
had been assembled in one corner,[fn.
10] whereas Sue ware
was lined up along the platform edge facing away from the mound.[fn.
11] Large quantities
of haniwa sherds were found in layers at the foot of the mound, and at the base of the platform
there was a high concentration of sherds stemming from the haniwa and Sue ware above (NIIRO 2005:5,
The stone chamber, measuring 4.7 × 2.5 m and the 4.4 m long passage that connected it to the outside world was built on the levelled surface of the original mountain, the base of the walls solidly buried, and drainage facilities dug in the floor of both the chamber and the passage (NIIRO 2005:22, 23).
The grave goods included accessories and weapons, armoury, horse gear, tools and pottery of which the accessories and part of the tools are reminiscent of items known from the Korean Peninsula. An 11.5 cm large bronze mirror [fn. 12] was recovered as were earrings [fn. 13] and a bronze bracelet of a type that is rare in Japan but reminiscent of pieces made from silver in the Peninsula. A multitude of beads were found along the walls of the chamber. Three long and two short swords [fn. 14] and 163 arrow points of iron were recovered in addition to the metal fittings from a quiver (NIIRO 2005:26-27).
Sue ware had been assembled and piled up at the entrance (Fig. 4), in one of the corners and at the
centre of one of the walls of the chamber. Also at the entrance and at one of the walls there were concentrations
of horse gear. The Sue ware and the horse gear at the inner walls of the chamber proved to be earlier
than that at the entrance, stemming from the middle and later part of the 6th century respectively.
Activities involving the use of fire – reminding us of the whitish burnt earth next to the top of the chamber – had left traces inside the chamber in the shape of pieces of charcoal found in the layer closest to the floor, in some places sparsely distributed, but in others in big black lumps. However, there was no burnt soil inside the chamber, and no traces of heating activities, so these pieces must stem from organic material burnt either outside the chamber or inside it but in a vessel, before being spread on the floor (NIIRO 2005:25).
From the artefacts recovered in- and outside the mound, the date of construction of Nima-Ōtsuka could be assessed to the middle of the 6th century. It is thus one of the oldest keyhole shaped mounds with a passage grave in Kibi, and the prototype of mounds to be built later in the region (NIIRO 2005:29).
As was the case with Tenguyama, Nima-Ōtsuka also clearly demonstrates the connection that the political leaders in Mabi must have had to the Korean Peninsula by part of its grave goods and by the construction of the burial chamber itself, here not as a deeply situated vertical grave, as was the case at the earlier Tenguyama, rather now as a passage grave accessible also after the initial burial had taken place. In fact, re-entrance into Nima-Ōtsuka seems likely to have been the case based on the two temporally different assemblages of Sue ware and horse gear within the chamber. The height of 1.65 m inside the passage and 2.5 m inside the chamber would have made access relatively easy and allowed for performing activities inside the chamber.
From Nima-Ōtsuka and the mid-6th century we return to Shōbuzako that is contemporary with Tenguyama, and whose keyhole shape is likewise of the scallop variation. It is by now proved to be 42 m long of which 29 m constitutes the round part, and surrounded by a moat (Map 3). It is placed on a small hillock 200 m east of Nima-Ōtsuka and 500 m west of Tenguyama. Its shape has been confirmed during the surveys and excavations taking place over the last seven years, and it adds to the likelihood of the king buried here belonging to the same lineage as those buried in these mounds (Okayama Daigaku Kōkogaku Kenkyūshitsu 2005:1).
Map 3: Contour of Shōbuzako Kofun.
Numerous students of Okayama University have participated in the excavations of Shōbuzako. Each year
new students, who are in the earlier phase of their studies at the archaeological department join the
excavation, and others, who have just completed their masters, leave it. Some of the people currently
working here are in the last year of their master’s course, and they have been digging at Shōbuzako
every year in March almost since investigations started in 2000.
From 2001 to 2005 new trenches were cut every year into various parts of the mound, crossing the perimeter of what was believed from the beginning to be the square and round parts respectively, in order to verify firstly the shape of the mound, and secondly the presence of a moat encircling it. And eventually, the trench that had been dug all the way from the end of the square part into the centre of the round was widened, deepened and made permanent in order to offer the excavators an entrance.
Contrary to the investigations at both Tenguyama and Nima-Ōtsuka, the ones carried out at Shōbuzako have never led to finds of haniwa that can be related to the mound (Okayama Daigaku Kōkogaku Kenkyūshitsu 2007:1).
In 2003, work was begun to locate the grave itself, and a multi-angular field measuring approximately 40m2 was opened at the top of the mound. This field was to develop into a shaft as it became still deeper over the following two years of excavation.
In 2004, the shaft dug from the top of the mound disclosed an area with a different quality of soil, slightly dislocated from the centre of what would later be detected was a dome-like feature built over the grave. Most likely, this interruption was caused by the subsequently realised collapse of one of the large stone slabs that covered the grave, resulting in the whole sequence on top of it caving in.
As the team worked its way down the shaft, the details of a highly interesting and complicated mound
construction became clear. After the stone coffin had been built on the ground and sealed with clay,
reddish earth was piled up on top of it till it formed a circular dome with a flat top and a flat circumference.
This round structure had been built carefully and coherently over the chamber where it rose to a height
of 1.5 m (Fig. 5). Two more layers of red soil were added on top of the circumference soil, leaving
the centre of the dome. Then a yellowish brown layer followed by a blackish brown layer, each measuring
approximately 50 cm, were added. However, in between these two layers a ring of black soil was added,
just thick enough to neutralise the sloping down of the layers. After these painstaking arrangements
had been completed, the construction of the rest of the mound had been interrupted and reinitiated countless
times, since the following layers consisted of innumerable small units of different qualities of soil
in order to shape the mound, until it had a total height of ca. 10 m. (Okayama Daigaku Kōkogaku Kenkyūshitsu
2005:1-8; Okayama Daigaku Kōkogaku Kenkyūshitsu 2006:1-7).
Fig. 5: Dome of reddish earth with flat top, unearthed in 2005.
Fig. 6: The chamber covered with pale clay, from west.
In 2006 an untouched layer of clay covering the coffin was reached, and apart from the broken cap
stone, the intact state of the grave realised (Fig. 6). Facing the chance of observing and excavating
a grave unlooted and unexcavated by earlier researchers, Professor MATSUGI applied for, and obtained,
funding to prolong the season of excavation this year, initially for an extra month, but eventually
for a total of four months, meaning that the investigations are finally to come to an end in June this
year (Figs. 7-17).
Fig. 7: Shōbuzako Kofun from west. A tent has been erected next to the mound to accommodate the team-members, who are night-watching in turn. (photo by author)
Fig. 8: SKURODA Yusuke and FUJIHARA Maya preparing the total station at the beginning of the day... (photo by author)
Fig. 9: ...followed by adjusting the levelling instrument. Here MIYOSHI Motoki and... (photo by author)
Fig. 10: ...ARATA Keisuke.
Fig. 11: HATANAKA Kōsuke.
Fig. 12: Seiji signalling to the total station. (photo by author)
Fig. 13: A member of the team.
Fig. 14: YAMANASHI Chiaki measuring for plan drawing.
Fig. 15: MIYOSHI Motoki and MIZUNO Hotaru in discussion. Southwest corner in background. (photo by author)
Fig. 16: Stratigraphical sequence of the northern wall. (photo by author)
Fig. 17: Professor MATSUGI considering the procedure. (photo by author)
During the current excavation season the chamber, originally constructed as a stone frame around
an inner wooden coffin, was opened and examined (Figs. 18-27).
Fig. 18: The grave placed slightly obliquely in the east-west oriented mound. East-end to the left with the broken capstone. The shape of the dome is visible opposite. From north. (photo by author)
Fig. 19: The southern end of the grave covered with a layer of clay.
Fig. 20: The cavity created by the broken capstone that is still in situ.
Fig. 21: MATSUGI Takehiko takes a thorough look inside the grave after earth has been removed.
Fig. 22: The broken capstone, however, – being still in situ – limits the view.
Fig. 23: MIZUSHIMA Yō'ichirō…
Fig. 24: …in discussion with Professor MATSUGI.
Fig. 25: Meeting at the end of the day... (photo by author)
Fig. 26: ...discussing results and planning further steps to be taken. NAKAHARA Kaori, MORI
Masahiro and KATAYAMA Kentarō...
Fig. 27: ...before watering the clay layer (HIROYA Fujii) and covering up the field. (photo by author)
The building of the chamber before erecting the mound is reverse to the usual sequence in which initially the mound would be constructed, and subsequently the grave established by digging a vertical shaft hole from its top. The sequence employed at Shōbuzako explains the depth of 4 m from the surface of the mound to the bottom of the chamber, and this circumstance is what has saved the grave from being looted.
The chamber had been closed by eight oblong capstones (Fig. 28), which may have been covered by a
layer of red colour, since traces of red pigments were recovered on parts of their upper surface. Gaps
between the capstones had been filled with round pebbles and small angular stones and everything had
been sealed with bluish-grey clay. After many months of observing and measuring, the excavators removed
the clay, observed the condition of the capstones and finally removed these in order to investigate
the inside of the grave itself (Figs. 29-34).
Fig. 28: The chamber with cleaned capstones, from east. (courtesy of MATSUGI Takehiko)
Fig. 29: Opened coffin, from east. (courtesy of MATSUGI Takehiko)
Fig. 30: A lump of the clay lining from the inside of the coffin with traces of red pigment. (photo by author)
Fig. 31: A bundle of arrowheads. (courtesy of MATSUGI Takehiko)
Fig. 32: Armour. (courtesy of MATSUGI Takehiko)
Fig. 33: Horse-trappings with bronze rosettes. (courtesy of MATSUGI Takehiko)
Fig. 34: Whetstones and Haji ware. (courtesy of MATSUGI Takehiko)
The interior of the chamber measured 3.6 × 1.2 m and the height of its walls was 60 cm (Fig. 92). Also the interior of the walls had been worked with clay (Fig. 30); this had been fitted into gaps between corner stones and levelled down to fit the height of the walls. The floor had been covered by round pebbles before placing the wooden coffin. The coffin itself had decayed, but three sets of iron cramps, presumably used as clasps on the coffin, were located in opposite positions along the walls. Iron nails were found at both ends of the chamber, and traces of wooden material were discovered between the capstones and the walls. The purpose of either of these materials however, is as yet unclear.
What met the eyes of the excavators when they removed the capstones was a set of armoury in almost perfect shape together with additional grave goods and the skull of the person buried there. At the time of writing this, the chamber has still not been thoroughly excavated, and accumulated sand hinders a full view of its contents. However; information of the finds visible at the surface is available. The deceased had been placed with his head to the east. Bones of his skull, including some teeth, were found resting on a bronze mirror. The rest of the grave goods were concentrated in the western half of the chamber. From the corpse’s waist to the area around its feet had been placed at least two bundles of iron arrowheads (Fig. 31) [fn. 15] and two swords, the latter accompanied with some wooden material. The most conspicuous object, a suit of iron armour, was placed about 50 cm from the western end (Fig. 32).[fn. 16] Its surface was covered with organic material, probably the remains of wrapping. Between the cuirass and the end wall was found a set of horse trappings. The iron bit and the bronze rosettes [fn. 17]remained (Fig. 33), exhibiting wear of the leather bridle originally fastened to them. The rosettes were extraordinarily shaped into S-curving cylinders from which rows of small bells were suspended.
Next to the trappings, in the north-western corner, a third bundle of iron arrowheads had been placed.
two spearheads of iron were recovered, one with a long hilt varnished with black lacquer,[fn.
19] and pointing from the
feet of the deceased towards the south-western corner of the chamber. The other does not have a visible
hilt; it is placed at the opposite side of the cuirass.
Apart from the metal ware, also two whetstones and a pair of small sized Haji ware (Jap. hajiki 土師器) jars were found in the chamber, placed together along the southern wall (Fig. 34).
Like Tenguyama and the later Nima-Ōtsuka, Shōbuzako bears clear evidence of connections to and influence from the burials built in the Korean Peninsula. The rich use of clay when building the chamber and the process of constructing the mound itself both originate in the southern part of the Korean Peninsula. It is also in this area that we find the insertion of wood in the construction of the stone chamber, which phenomenon has been observed here in chambers earlier than that of Shōbuzako. It is furthermore likely that the origin of the cylindrical bronze rosettes should be traced to the Peninsula.
The combination and styles of the grave goods place the building of Shōbuzako in the latter half of the 5th century,[fn. 20] temporarily with Tenguyama, and in the Yūryaku dynasty period. It turned out to be the content of the grave itself that assessed Shōbuzako’s date of construction. None of the sherds of haniwa and Sue ware, recovered over the years of investigations in various trenches and in the earth accumulated in the moat had been in a position to clearly verify their connection to the mound itself (Okayama Daigaku Kōkogaku Kenkyūshitsu 2007:1-2).
The discontinuity in Kibi in the late 5th century of the building of giant and large scale kofun mounds like Kamo-Tsukuriyama, Misu-Tsukuriyama and Ryōgūzan is sometimes seen as indicating that the elite here suffered a restriction of power by the great kings in the Kinai 畿内 region (Map 1). This discontinuity however, can be observed all over western Japan. Even the Furu'ichi 古市 and the Mozu 百舌鳥 kofun clusters in Ōsaka 大阪 that represent leaders in what we assume must have been the most powerful region of all, move towards a stop in terms of construction of large scale mounds at exactly the same point of time (MATSUGI ed. 2001:64).
Furthermore, the excavations and surveys executed by the archaeologists at Okayama University show that mounds were constructed in Kibi in the latter half of the 5th century, although in a more moderate scale than the large examples from the beginning of the century. Particularly many more scallop shaped mounds were erected, among these Shōbuzako and Tenguyama, and in all areas of Kibi they came to mark the landscape together with regularly keyhole shaped mounds. So, "was it the political relations of the people in power in Kibi that changed, or was it the meaning inherent in the keyhole shaped mound itself?", ask the researchers in one of their excavation reports from Shōbuzako (Okayama Daigaku Kōkogaku Kenkyūshitsu 2006:7). They are on their way to answering the question through the ongoing investigations that they carry out together with their students. So far, the answer seems to be that the keyhole shaped mounds themselves came to have new and weaker connotations during the late 5th century, and that some of the shape’s earlier connotations of supremacy were taken over by that of the scallop shaped mounds.
The Nima section in Mabi, however, is one of the few areas of Kibi in which construction of burial mounds continued after the turn of the 6th century, and the rich graves found here that stem from the later half of the 5th century constitute a prelude to the turn things took in the following period.
As was the case with Tenguyama, Shōbuzako Kofun has proved to be the grave of one of the strong leaders of the Nima area in the late 5th century. The image of the deceased person buried here in a highly complex chamber is that of a powerful person with a strong air of militarism around him, an image derived from his grave goods dominated by weapons and armoury. Particularly the cuirass is believed to be a piece of armoury associated with Kinki power - leading in the production and distribution of armoury -; it demonstrates the military connection of the deceased to the political power held by the supreme kings in Yamato.
In other words, the researchers continue, in the process of abolishing the maintenance of supreme rulers inside certain areas such as those interred in Kamo-Tsukuriyama and Misu-Tsukuriyama, a situation arose in which the leaders of other areas, areas that had previously supported the few supreme areas, became connected in and by their own power. Furthermore, these new, though less hegemonic leaders, held connections not only to each other but also to leaders in other regions inside as well as outside the Japanese archipelago using their political power, which relations at one time strengthened their position and caused them to compete. Shōbuzako and the nearby located Tenguyama make up two of the burials belonging to this new situation of social upheaval.
However, by the start of the 6th century, the chambers of burial mounds began to be built with a passage as was the case at Nima-Ōtsuka, which shows that, once again, a change had taken place in the meaning of the mound and in its relation to society. Large scale changes and reorganisations took place in the surrounding society leading ultimately to the ritsuryō 律令 nation[fn. 21] .
In the early 6th century, Late Kofun, the Nima area, which held no mounds at all until the middle of the 5th century, rose to power. While several areas within Kibi came to a complete stop in terms of mound building of any shape, the Nima area, which offers a unique concentration of scallop shaped mounds, and which houses one of the oldest passage graves in Kibi, can be viewed as the headquarter of a leading dynasty that came to hold the concentrated power of Kibi half a century or more after it had waned in the areas of the giant tombs of Kamo-Tsukuriyama and Misu-Tsukuriyama (Okayama Daigaku Kōkogaku Kenkyūshitsu 2006:7).
By detailed comparative research of Tenguyama and Shōbuzako on the one side, and Nima-Ōtsuka on the
other, it is the hope of the researchers at Okayama University to be able to demonstrate how one type
led to the other (Okayama Daigaku Kōkogaku Kenkyūshitsu 2007:1-2).
First of all, I would like to thank Professor MATSUGI for inviting me to visit the excavation of the Shōbuzako Kofun in early March 2007, thus giving me an excellent opportunity to experience one of the important archaeological investigations constituting the Yūryaku dynasty project, which he and Professor NIIRO have been carrying out over the last decade together with their students, and which will continue next year, when the first steps of examining a new burial mound will be taken. Also, I want to thank Professor MATSUGI for reading and commenting on this article and for following up on the account by sending me the report from the current year’s excavation within days after completing it together with fresh pictures, thus providing the article with some of its most crucial details, namely those dealing with the content of the chamber of Shōbuzako.
I also want to express my appreciation to the students working at Shōbuzako for kindly introducing me to the details of the excavation during my visit, and for including me in their team in spite of the disturbance of their daily routine that my presence must have caused.
In addition, I want to thank Professor MATSUMOTO Naoko 松本直子, Okayama University, for sending me the material on Tenguyama and Nima-Ōtsuka Kofun which constitutes substantial parts of this article and for answering my questions on a number of details, and I want to thank Professor NIIRO Izumi for sending me the pictures of Nima-Ōtsuka Kofun.
Finally, I want to thank Barbara SEYOCK for valuable comments on and help with numerous details within the article and Michael MOOS for producing the maps used here and for his work with the photos.
1) A thorough survey (to be carried out over a three year period) of the Kamo-Tsukuriyama Kofun has been initiated by Professor NIIRO Izumi 新納泉, Okayama University, employing digital equipment for accurate measurements. With its 360 m it is the 4th largest keyhole shaped mound in all of Japan and it is fortunately not categorised as a 'royal tomb' like other gigantic tumuli, meaning they are untouchable not only in terms of actual excavation, but also in terms of surface observation (NIIRO and ISHISAKA (ed.) 2006:1).
2) Yūryaku 雄略 is the posthumous name for a ruler of the late 5th century called Waka Takeru (Ohohatsuse no Wakatake 大泊瀨幼武) according to the 8th century chronicles, the Kojiki 古事記 and the Nihon Shoki 日本書紀. He is mentioned in the Chinese chronicles for sending a letter to the Chinese emperor together with four other "kings", and his name appears on two swords excavated from Saitama 埼玉 and Kumamoto 熊 本 Prefectures respectively. According to tradition, he was the 21st emperor. Thus, Yūryaku does not refer to any ruler within Kibi, but is the name used for the period in question.
3) Digital measurements make up an important part of the whole project. Contour lines are transferred to three-dimensional representations of the excavated mounds. Registering the height above sea level of countless points using a total station that transmits all information to a central computer ensures the standardisation of all information from all excavations and surveys.
4) Basically of keyhole shape, but whereas regular keyhole shaped mounds have square parts at least half as long as the diameter of their round parts, the square parts of scallop shaped mounds are much shorter and lower than their round parts.
5) When Tenguyama was digitalised the whole mound was covered with markers with a mutual distance of 50 cm. The heights of all of these were used to create a Digital Elevation Model (DEM), after which the results were transferred to a map constituted by 50 cm meshes. In order to make up for the many changes in obliqueness of the mound, TIN (Triangulated Irregular Network) was uses in addition to the meshes, meaning that numerous randomly picked points were measured in terms of height, and joined with lines thus shaping triangles of various shapes (MATSUGI ed. 2001:27).
6) I.e. a chamber that had been closed from its top and covered by the top of the mound, thus not meant to be accessible after the initial burial.
7) This is the angle created where the round and the square parts meet.
8) I.e. cylindrical haniwa with walls divided by raised bands into four sections of which the second and sometimes also the third from the bottom had been equipped with round holes (MATSUGI ed. 2001:19).
9) The ceremonial platform constitutes a section protruding to one side near the constriction between the round and the square parts. The sherds from the platform all belonged to bowls or lids of these. Also Sue ware was recovered from the annex Tenguyama-Nishi mound (MATSUGI ed. 2001:23-25).
10) It is the corner closest to the constriction.
11) Of both these types of artefacts also only the bases remained, however, one haniwa was identified as being of house shape, and three others are thought to be of human figures. The line of Sue ware consisted of a bowl, three large pots and a footed jar. The entire record of Sue pottery from the exterior of the mound stemmed from the platform (NIIRO 2005:9, 11).
12) The mirror shows saw-tooth pattern on its inside and depictions of five beast on its outside.
13) Three pairs and a single item have been found.
14) The sword lengths are 111 cm, 96 cm, 69 cm, 36 cm, and 31 cm.
15) All are of long-necked slender type (Jap. chōkei-shiki 長頸式).
16) It is a cuirass made of horizontal strips of iron riveted together (Jap. yokohagiita byōdome tankō 横矧板鋲留短甲).
17) These devices are thin metal plates of various shapes and with various decorations placed at each side of the mouth of the horse, serving the function of holding the bit in the right position as this was fastened to them.
18) Most of these are of the type described above, but a few are of short triangular type (Jap. tankei sankaku 短茎三角).
19) The surface of the hilt seems at the present to have consisted of bark.
20) The Haji pottery however, is rare as grave good for the period in question.
21) The ritsuryō code, a set of laws and regulations stemming from the beginning of the 8th century, assessed the right of aristocratic families to be exempted from tax, and the hereditary authority of the emperor as well as of government officials.
MATSUGI Takehiko (ed.) 2001, Kibi Chiiki ni Okeru "'Yūryaku-Chō' Ki" no Kōkogaku-teki Kenkyū (Archaeological research into the Yūryaku-dynasty period in Kibi Region): Kagaku Kenkyūhi Hojokin (Kiban Kenkyū(B)(2)) Kenkyū Seika Hōkokusho, Heisei 9 Nendo – Heisei 12 Nendo, Okayama [松木武彦: 「吉備地域における「『雄略朝』期」の考古学的研究 科学 研究費補助金基盤研究: 科学研究費補助金(基盤研究(B)(2))研究成果報告書; 平成9年度〜平成12年度」. 岡山].
NIIRO Izumi 2005, Okayama-Ken Kibi-Gun Mabi-Chō Nima-Ōtsuka Kofun (Nima-Ōtsuka Kofun in Mabi Town, Kibi District, Okayama Prefecture). Okayama [新納泉: 「岡山県吉備郡真備町仁万大塚古墳」. 岡山].
NIIRO Izumi; ISHISAKA Daiji (ed.) 2006, Tsukuriyama Kofun Dai 1 Ji Sokuryō Chōsa Hōkoku (Report of the 1st survey of the Tsukuriyama Kofun). Okayama [新納泉, 石坂泰士 [編]: 「造山古墳第１次測量調査報告」. 岡山].
Okayama Daigaku Kōkogaku Kenkyūshitsu; Shōbuzako Kofun Dai 5 Ji Hakkutsu Chōsa Dan (ed.) 2005, Shōbuzako Kofun Dai 5 Ji Hakkutsu Chōsa: Genchi Setsumei Shiryō (Report of the 5th excavation of the Shōbuzako Kofun: Field Briefing Material). Okayama: Okayama Daigaku Kōkogaku Kenkyūshitsu [岡山大学考 古学研究室・勝負砂古墳第5次調査団 [編]: 「勝負砂古墳第5次調査: 現地説明資料」岡山: 岡山大学考古学研究室].
Okayama Daigaku Kōkogaku Kenkyūshitsu; Shōbuzako Kofun Dai 6 Ji Hakkutsu Chōsa Dan (ed.) 2006, Shōbuzako Kofun Dai 6 Ji Hakkutsu Chōsa: Genchi Setsumei Shiryō (Report of the 6th excavation of the Shōbuzako Kofun: Field Briefing Material). Okayama: Okayama Daigaku Kōkogaku Kenkyūshitsu [岡山大学考 古学研究室・勝負砂古墳第6次調査団 [編]: 「勝負砂古墳第6次調査: 現地説明資料」. 岡山: 岡山大学考古学研究室].
Okayama Daigaku Kōkogaku Kenkyūshitsu; Shōbuzako Kofun Dai 7 Ji Hakkutsu Chōsa Dan (ed.) 2007,
Shōbuzako Kofun Dai 7 Ji Hakkutsu Chōsa: Genchi Setsumei Shiryō (Report of the 7th excavation of
the Shōbuzako Kofun: Field Briefing Material). Okayama: Okayama Daigaku Kōkogaku Kenkyūshitsu [岡山大学考
古学研究室・勝負砂古墳第7次調査団 [編]: 「勝負砂古墳第7次調査: 現地説明資料」. 岡山: 岡山大学考古学研究室].
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