A study on the possible construction order of the temples in Mahendraparvata on the summit of Kulen Mountain, Cambodia, based on brick and sandstone materials

The Angkor monument is a group of temples built between the 9th and 15th centuries. Mahendraparvata, the first capital of the Angkor Empire, was built by King Jayavarman II on the summit of Kulen Mountain, ~35 km northeast of Siem Reap, Cambodia. In this study, we investigated the building materials of the 18 temples that make up Mahendraparvata and found that mainly bricks were used in the construction of temples in Mahendraparvata. Gray sandstone, derived from the Phu Kradung Formation (the Red Terrain Formation) of the late Jurassic to early Cretaceous age (distributed in the southeastern foothills of Kulen Mountain and widely used throughout the Angkor monument), was used in small quantities at the door frames, stairs, and lintels of the temples. Chemical composition measured with a portable X-ray fluorescence analyzer and magnetic susceptibility measured with a portable magnetic susceptibility meter were conducted on the brick and sandstone materials, and the thickness of the bricks was also measured. On the basis of the magnetic susceptibility and Rb content of the bricks, the 18 investigated temples were categorized into three groups: Groups A, B, and C. The Rb content of the gray sandstone revealed that Group A differs from Groups B and C. Temples in Group A, namely Prasat O Phaong, Prasat Khmum, and Prasat Kraham (I & II), are aligned in a straight line, and Prasat O Phaong, Prasat Rong Chen, and Prasat O Top are also aligned in a straight line. The intersection of these two lines is at Prasat O Phaong. This suggests a possible relationship among the temples in Group A. Temples in Group A tend to be in better condition than those in other groups. The thickness of the bricks used in the temples of Mahendraparvata is between the thickness of bricks used in the Sambor Prei Kuk monument from the pre-Angkorian period and those of the temples of Hariharalaya, the next capital after Mahendraparvata. During these periods, there was an overall trend of decreasing brick thickness over time, suggesting a technical connection among these monuments.