9:15 AM - 9:30 AM
[MIS10-02] Origin of stone materials in stone structures made by Kawaroku, a stonemason active in Inaba Province at the end of the Edo period
Keywords:cultural geology, magnetic susceptibility, cultural property, stone, San'in Kaigan Geopark, geopark
Rokurobei Ozaki (a.k.a. “Kawaroku”, birth date unknown - died in 1865, Tottori City Aoyakyodokan, 2016), a stonemason active mainly in the Aoya area of present-day Tottori City in the late Edo period, is said to have made komainu (guardian dogs) and lanterns using locally produced andesite (Omori, 2007). However, petrographic descriptions of Kawaroku's works have not been provided, and the rocks' provenance was unclear. Emura et al. (2025) made naked-eye observations of stone structures in Kawaroku's works and clarified that the stone materials can be roughly classified into andesite and basalt. In this presentation, we will estimate the candidate of stone production site by comparing the rock descriptions and magnetic susceptibility of the stone structures of Kawaroku and an outcrop. This study will provide basic data to clarify one aspect of the geological resources of stone and its consumption in the Inaba area during the late Edo period.
The geology of the study area is based on the Pliocene Kamejiri Basalt in the Kamejiri district of Aoyacho, Tottori City, covered by Pliocene andesitic lava called Hachibuse andesite, with rivers flowing between the mountains formed by each lava flow and river deposits in the plain areas (Murayama and Osawa, 1957). The Kamejiri basalt is composed of basalt in the upper part and coarse-grained basalt in the lower part (Murayama and Osawa, 1957).
The survey targets 38 stone structures in the list of Kawaroku products in Aoyakyodokan, Tottori City (2016) and an outcrop in the Kamejiri area, Aoyacho, Tottori City. The stone structures are distributed in western Tottori City and eastern Yurihama Town, Tottori Prefecture. The outcrop is the site of a quarry for the commonly known “Kamejiri stone”. During the survey, the rocks were observed with the naked eye, and the magnetic susceptibility was measured and described with a microscope. The magnetic susceptibility was measured at a point where the surface of the rock was as flat as possible, and where the radius of the edge of the stone structure was at least 64 mm from the center of the sensor of the magnetic susceptibility meter and the thickness of the stone structure was at least 38 mm.
The observations of thin section shows that the rocks of lower part of Kamejiri basalt is isogranular in textur, and contained plagioclase, peridotite, and ordinary pyroxene, the maximum size of which was about 2 mm. The lower part of the Kamejiri Basalt is isogranular, but in this study, it is referred to as basalt for convenience, following the previous study. The lithology of the lower part of the Kamejiri basalt and some of the stone structures (many Jizoson and komainu) in the basalt are similar. The minimum and maximum averaged values of the magnetic susceptibility of 20 measurements of these stone structures are 2.58 × 10-3 [SI] and 5.79 × 10-3 [SI], respectively, and the magnetic susceptibility of the outcrop of the lower Kamejiri basalt layer is 4.18 × 10-3 [SI]. Although both lithologies are similar, According to T-test result on the lithologies and outcrops, and significant differences are found. From these results, it could not be inferred that the lower Kamejiri basalt outcrop was used for some of the stone structures made by Kawaroku. However, since only one outcrop was measured and the lithology itself is similar, we would like to take further data and deepen our discussion. As a future prospect, we plan to search for outcrops that are candidates for stone production sites and compare them with the stone structures.
The geology of the study area is based on the Pliocene Kamejiri Basalt in the Kamejiri district of Aoyacho, Tottori City, covered by Pliocene andesitic lava called Hachibuse andesite, with rivers flowing between the mountains formed by each lava flow and river deposits in the plain areas (Murayama and Osawa, 1957). The Kamejiri basalt is composed of basalt in the upper part and coarse-grained basalt in the lower part (Murayama and Osawa, 1957).
The survey targets 38 stone structures in the list of Kawaroku products in Aoyakyodokan, Tottori City (2016) and an outcrop in the Kamejiri area, Aoyacho, Tottori City. The stone structures are distributed in western Tottori City and eastern Yurihama Town, Tottori Prefecture. The outcrop is the site of a quarry for the commonly known “Kamejiri stone”. During the survey, the rocks were observed with the naked eye, and the magnetic susceptibility was measured and described with a microscope. The magnetic susceptibility was measured at a point where the surface of the rock was as flat as possible, and where the radius of the edge of the stone structure was at least 64 mm from the center of the sensor of the magnetic susceptibility meter and the thickness of the stone structure was at least 38 mm.
The observations of thin section shows that the rocks of lower part of Kamejiri basalt is isogranular in textur, and contained plagioclase, peridotite, and ordinary pyroxene, the maximum size of which was about 2 mm. The lower part of the Kamejiri Basalt is isogranular, but in this study, it is referred to as basalt for convenience, following the previous study. The lithology of the lower part of the Kamejiri basalt and some of the stone structures (many Jizoson and komainu) in the basalt are similar. The minimum and maximum averaged values of the magnetic susceptibility of 20 measurements of these stone structures are 2.58 × 10-3 [SI] and 5.79 × 10-3 [SI], respectively, and the magnetic susceptibility of the outcrop of the lower Kamejiri basalt layer is 4.18 × 10-3 [SI]. Although both lithologies are similar, According to T-test result on the lithologies and outcrops, and significant differences are found. From these results, it could not be inferred that the lower Kamejiri basalt outcrop was used for some of the stone structures made by Kawaroku. However, since only one outcrop was measured and the lithology itself is similar, we would like to take further data and deepen our discussion. As a future prospect, we plan to search for outcrops that are candidates for stone production sites and compare them with the stone structures.