Weathering processes and mapping of rock’s damage category using GIS at Yoshimi region, Japan

Japan is one of the countries that has a considerable number of archaeological sites that are dated back to thousands of years and are of value. They, as well as many archaeological sites worldwide, suffer weathering to different limits of damage categories. Specification of damage category of such ancient sites is of value for the decision of conservation. The current study aims to find out the prevailing weathering processes acting on the archaeological sites at the Yoshimi area. Also, it aims to map damage categories defined by field survey using a geographic information system (GIS 10.1) program, numerical specification of rock’s damage categories applying the magneto-structive ultrasonic waves for measuring the velocity of the ultrasonic waves (Cp) at specific measuring points in the field. The rock’s salt content has also been examined in the laboratory for small size representative rock samples at the Yoshimi region to find out the main reasons behind the prevailing weathering at the study area. Rock’s petrography and mineral composition using a transmitting polarizing microscope and a scanning electron microscope indicated meta-sediments at the Yoshimi site with diagenetic kaolinite. The damage category at caves 2 and 3 is higher than that at cave 1 as indicated from field survey as well as laboratory measurements of Cp and rock’s salt content. Mapping with GIS confirms that field specification of damage categories is highly matching with laboratory study for these caves. Chemical weathering and mechanical weathering are acting at these sites creating diagenetic kaolinite, micro-cracks, rock deformation up to rock powdering. Salt weathering acts through crystallization of chlorides and hydration of sulfates. Frost weathering as well as biological weathering by algae and plants deforms these sites that are of historical value.