Using Magnetic Susceptibilities of the Sandstone Blocks to Determine the Construction Period of the Revetment of the Surrounding Moat of the Angkor Wat Temple, Cambodia

In the Angkor monument located in Siem Reap Province, Cambodia, temples surrounded by moats are commonly seen. However, examples of surrounding moats protected with stone blocks such as sandstone (gray to yellowish-brown sandstone) and laterite are not common. The surrounding moat of the Angkor Wat temple, representing the Angkor monument, is one of the few temples surrounded by a moat revetted with sandstone and laterite blocks. The Angkor Wat temple is the pinnacle of the Khmer architecture, and was founded by King Suryavarman II in the first half of the 12th century. Sandstone and laterite blocks were mainly used in its construction. The Angkor Wat temple is surrounded by a moat 1.5 km long E-W, 1.3 km long N-S, and 190 m wide. Magnetic susceptibility measurements were carried out on the sandstone blocks that make up the revetment to clarify its construction period. The mean magnetic susceptibilities of the sandstone blocks at each area of the structures inside the surrounding moat are relatively high, ranging from 3.1 to 4.0 × 10^？3 SI units. In contrast, the mean magnetic susceptibilities of the sandstone blocks at each area of the revetment of the surrounding moat, except for the central part of the revetment of the western surrounding moat, are lower, ranging from 2.0 to 2.9 × 10^？3 SI units. These magnetic susceptibility values correspond to those of the sandstone blocks used in the early Bayon-style period, indicating that the moat revetment was likely constructed during this period (the late 12th century to the early 13th century), slightly later than the structures inside the surrounding moat. There is a clear discontinuity between the central part of the moat revetment on the west side and the rest of the revetment, and much of the latter has collapsed. Judging from the degree of collapse and the clear boundary between the two, the latter is presumed to have been built later than the former. Considering the limited number of the sandstone blocks still present along the inner side of the surrounding moat and the lack of stepped structures, revetment may not have been undertaken on the inner side of the surrounding moat of the Angkor Wat temple except for the central part in the western side.