5:15 PM - 7:15 PM
[O05-P07] Geological background of stone materials from Kinki area that were widely distributed from the Ancient to the Medieval Period
★Invited Papers
Keywords:hyaloclastite, granite, stone material, stone structure, archaeology, culture geology
1 Introduction
The study of stone structure is a major topic in archaeology. The main research method is tracing the genealogy of stone structure from their morphology using detailed measured drawings. Furthermore, in recent years, the origins of stone materials have been identified through methods such as magnetic susceptibility measurements. As a result, it has been revealed that some stone materials from certain regions were distributed over a wide area.
Representative stone materials that were widely distributed before the Middle Ages include Tatsuyama stone from Takasago City, Hyogo Prefecture, Hibiki stone from Takahama Town, Fukui Prefecture, and Mikage stone from the Rokko Mountains in Hyogo Prefecture.
2 Tatsuyama stone and Hibiki stone
Tatsuyama stone is a Cretaceous volcaniclastic rock known for being used as sarcophagus material in the Kofun period, having been distributed from the Kinki region to the Seto Inland Sea coastal region.
Ozaki and Harayama (2013) revealed that Tatsuyama stone is hyaloclastite of rhyolite origin that erupted into a Cretaceous caldera lake.
Most of the Cretaceous extrusive rocks in the Chugoku region consist of extremely hard welded tuff, which is unsuitable for processing. In contrast, Tatsuyama stone has both durable and soft enouph to be easily processed (Takasago City Board of Education, 2014). This is due to the fact that the rock is hyaloclastite.
Hibiki stone is Miocene andesite and its stone structures were distributed along the Sea of Japan coast from the Tohoku region to northern Kyushu during the Medieval Period. Most Hibiki stone is composed of autoclastic lava or hyaloclastite, and because the rock fragments and matrix are cemented together, it is easier to process than other Miocene tuffaceous rocks or andesite lava.
As mentioned above, the fact that both Tatsuyama stone and Hibiki stone are hyaloclastite probably gave them an advantage as stone materials.
3 Mikage stone
Cretaceous to Paleogene granites are widely distributed in Southwestern Japan, and the Mt. Rokko region is one of them. Granite quarried at the foot of Mt. Rokko is called Mikage stone, and medieval stone structures made from it are distributed not only throughout the Kinki region, but also in the western Chugoku region, southern Shikoku and southern Kyushu. The reason why Mikage stone, which has a standard rock facies for granite, is distributed more widely than other granites is thought to be due to the geological and geographical conditions of the quarrying area rather than the rock quality.
The Mikage stone was quarried from boulders carried to the coast by debris flow, which is thought to have made it easier to transport the stones (Sakiyama, 2023). In addition to Mikage stone, Shirakawa stone in Kyoto and Kido stone in Shiga are known granites that have been quarried in the Kinki region since ancient times. Both the Shirakawa and Kido are areas where alluvial fans have developed and where debris flows have frequently occurred in the past. These facts suggest that medieval granite materials were obtained from rock masses transported by debris flows, rather than quarrying from cliffs. In particular, the foothills of Mt. Rokko, where Mikage stone is produced, face the Seto Inland Sea, and because stone was located near the coast, it became the largest source of stone during the medieval period, when transportation was difficult.
4 conclusion
As mentioned above, clarifying the rock characteristics and geological and topographical background of stone materials leads to understanding the history and culture of the region.
References
Ozaki, M. and Harayama, S. (2003) Geology of the Takasago district. Quadrangle Series, 1:50,000, Geological Survey of Japan, AIST, 87p. (in Japanese with English abstract 3p.).
Sakiyama, T. (2023) Why is "granite" called "Mikage stone"? - Inscribed stones brought about by debris flow. in Culture Geology in Tectonic Zones, Kyoto University Press, 120-132. (in Japanese)
Takasago City Board of Education (2014) Ishi-no-Hoden and Tatsuyama Stone Quarry Site - Detailed distribution survey report II of the Tatsuyama stone quarry site. Takasago City, 116p. (in Japanese)
The study of stone structure is a major topic in archaeology. The main research method is tracing the genealogy of stone structure from their morphology using detailed measured drawings. Furthermore, in recent years, the origins of stone materials have been identified through methods such as magnetic susceptibility measurements. As a result, it has been revealed that some stone materials from certain regions were distributed over a wide area.
Representative stone materials that were widely distributed before the Middle Ages include Tatsuyama stone from Takasago City, Hyogo Prefecture, Hibiki stone from Takahama Town, Fukui Prefecture, and Mikage stone from the Rokko Mountains in Hyogo Prefecture.
2 Tatsuyama stone and Hibiki stone
Tatsuyama stone is a Cretaceous volcaniclastic rock known for being used as sarcophagus material in the Kofun period, having been distributed from the Kinki region to the Seto Inland Sea coastal region.
Ozaki and Harayama (2013) revealed that Tatsuyama stone is hyaloclastite of rhyolite origin that erupted into a Cretaceous caldera lake.
Most of the Cretaceous extrusive rocks in the Chugoku region consist of extremely hard welded tuff, which is unsuitable for processing. In contrast, Tatsuyama stone has both durable and soft enouph to be easily processed (Takasago City Board of Education, 2014). This is due to the fact that the rock is hyaloclastite.
Hibiki stone is Miocene andesite and its stone structures were distributed along the Sea of Japan coast from the Tohoku region to northern Kyushu during the Medieval Period. Most Hibiki stone is composed of autoclastic lava or hyaloclastite, and because the rock fragments and matrix are cemented together, it is easier to process than other Miocene tuffaceous rocks or andesite lava.
As mentioned above, the fact that both Tatsuyama stone and Hibiki stone are hyaloclastite probably gave them an advantage as stone materials.
3 Mikage stone
Cretaceous to Paleogene granites are widely distributed in Southwestern Japan, and the Mt. Rokko region is one of them. Granite quarried at the foot of Mt. Rokko is called Mikage stone, and medieval stone structures made from it are distributed not only throughout the Kinki region, but also in the western Chugoku region, southern Shikoku and southern Kyushu. The reason why Mikage stone, which has a standard rock facies for granite, is distributed more widely than other granites is thought to be due to the geological and geographical conditions of the quarrying area rather than the rock quality.
The Mikage stone was quarried from boulders carried to the coast by debris flow, which is thought to have made it easier to transport the stones (Sakiyama, 2023). In addition to Mikage stone, Shirakawa stone in Kyoto and Kido stone in Shiga are known granites that have been quarried in the Kinki region since ancient times. Both the Shirakawa and Kido are areas where alluvial fans have developed and where debris flows have frequently occurred in the past. These facts suggest that medieval granite materials were obtained from rock masses transported by debris flows, rather than quarrying from cliffs. In particular, the foothills of Mt. Rokko, where Mikage stone is produced, face the Seto Inland Sea, and because stone was located near the coast, it became the largest source of stone during the medieval period, when transportation was difficult.
4 conclusion
As mentioned above, clarifying the rock characteristics and geological and topographical background of stone materials leads to understanding the history and culture of the region.
References
Ozaki, M. and Harayama, S. (2003) Geology of the Takasago district. Quadrangle Series, 1:50,000, Geological Survey of Japan, AIST, 87p. (in Japanese with English abstract 3p.).
Sakiyama, T. (2023) Why is "granite" called "Mikage stone"? - Inscribed stones brought about by debris flow. in Culture Geology in Tectonic Zones, Kyoto University Press, 120-132. (in Japanese)
Takasago City Board of Education (2014) Ishi-no-Hoden and Tatsuyama Stone Quarry Site - Detailed distribution survey report II of the Tatsuyama stone quarry site. Takasago City, 116p. (in Japanese)