9:15 AM - 9:30 AM
[HQR05-02] Use of volcanic ash for making earthenware revealed by the WDS analysis of volcanic glass in ceramic paste - Example for Usultan-style pottery in Chalchuapa, El Salvador -
Keywords:X-ray microprobe analyzer, Usulutan-style pottery, Arce tephra, Coatepeque
In volcanic area, volcanic ash is generally utilized for making pottery as one of materials. Then the chemical analysis of the volcanic glass contained in the paste of the pottery can provide available data to clarify the producing area of the pottery and also the producing method. Kitamura(2022) illustrated that a piece of Usulutan-style pottery, which was excavated in the La Cuchilla zone at the archaeological site of Chalchuapa, western El Salvador, contains volcanic glass originated from Arce Tephra by the analysis of chemical composition using wave-length-dispersion X-ray microprobe analyzer (WDS), and that volcanic ash of the Arce tephra is possible to be utilized selectively for making pottery.
The Arce Tephra is an extensive pumice fall (72 ka) originated from Coatepeque Caldera located in the neighbour area of Chalchuapa. While Kitamura (2017) devided the tephra into three units and demonstrated the chemical composition of each unit using WDS, Kutterolf, et al. (2020) devided it into 10 units, and clarified the chemical composition of volcanic glass by each unit. In this study, the chemical composition of volcanic glass contained in a piece of the Usulutan-style pottery, which was excavated in La Cuchilla zone at the archaeological site of Chalchuapa, were analyzed using WDS (JEOL JXA-8230) in the laboratory of Global Environment and Disaster Prevention Sciences, the Faculty of Science and Technology, Hirosaki University, and it was compared with that of each unit of the Arce Tephra analyzed by the same equipment.
The result of analysis of volcanic glass in ceramic paste shows bimodal compositoin, consistent with the middle unit (unit V) and the lower units (Unit III and IV) of the Arce Tephra. The chemistry of volcanic glass from the uppermost units (unit IX and X) shows mostly unimodal composition, consistent with one mode of the bimodal composition of the volcanic glass in the ceramic paste. The middle unit (unit V) and the uppermost units (unit IX and X) contain fine material so that they might be more useful for making pottery than the coarse pumice units (unit VI, VII and VIII).
The Arce Tephra is an extensive pumice fall (72 ka) originated from Coatepeque Caldera located in the neighbour area of Chalchuapa. While Kitamura (2017) devided the tephra into three units and demonstrated the chemical composition of each unit using WDS, Kutterolf, et al. (2020) devided it into 10 units, and clarified the chemical composition of volcanic glass by each unit. In this study, the chemical composition of volcanic glass contained in a piece of the Usulutan-style pottery, which was excavated in La Cuchilla zone at the archaeological site of Chalchuapa, were analyzed using WDS (JEOL JXA-8230) in the laboratory of Global Environment and Disaster Prevention Sciences, the Faculty of Science and Technology, Hirosaki University, and it was compared with that of each unit of the Arce Tephra analyzed by the same equipment.
The result of analysis of volcanic glass in ceramic paste shows bimodal compositoin, consistent with the middle unit (unit V) and the lower units (Unit III and IV) of the Arce Tephra. The chemistry of volcanic glass from the uppermost units (unit IX and X) shows mostly unimodal composition, consistent with one mode of the bimodal composition of the volcanic glass in the ceramic paste. The middle unit (unit V) and the uppermost units (unit IX and X) contain fine material so that they might be more useful for making pottery than the coarse pumice units (unit VI, VII and VIII).