As part of an international team, the paleogeographers from Lomonosov Moscow State University and the Institute of Geography of the Russian Academy of Sciences found out the exact foundation date of the fortress Por-Bazhyn in Tuva. Using a new modification of radiocarbon dating, the scientists found that the construction of the fortress began in the summer of 777. And its purpose was not fortification, as previously thought, but religious: it was a Manichaean monastery.
Por-Bazhyn is the ruins of an ancient adobe fortress on an island in Lake Tere-Khol in one of the most inaccessible areas of the Republic of Tuva. The ruins were first investigated in 1891 by Russian geographer and ethnographer Dmitry Klements. At the turn of the 1950s and 60s, the archaeologist Sev’yan Vainshtein conducted the first excavations here and proved that the fortress was built during the third Uyghur Khaganate in the 8th century. However, the exact dating of the monument according to excavation data could not be established.
In 2007-2008, on the initiative of Sergey Shoigu, large-scale excavations were carried out in the fortress area. The archaeologists have revealed an interesting fact: the fortress was not used at all after the construction. For this reason, the cultural layer inside the fortress was very poor. However, hopes for clarifying the date and goals of building the fortress by archaeological methods were not realized.
Then the scientific methods came to aid. In 2012, an article by the Japanese researchers was published in the journal Nature, which dated single tree rings of a 1800-year-old cedar and discovered a surge in the content of radiocarbon in the atmosphere in 775. The surge was associated with an abnormal outburst on the sun. This phenomenon began to be called the "Miyake event" (named after the first author of the article in Nature). The Russian scientists have decided to use the "Miyake event" to date Por-Bazhyn. In 2018, they turned for help to one of the world's leading radiocarbon dating laboratories, located at the University of Groningen in the Netherlands.
“We sent three slices of larch from the walls of Por-Bazhyn to Groningen. One of them, with reliably preserved bark, was selected for study. And in it, in the third ring from the bark, that same “Miyake event” was discovered! And the study of the youngest ring at the cellular level allowed the dendrochronologists from Groningen to determine that the tree was cut down in the summer. Thus, not only the year was established, but also the season of the construction start (the summer of 777),” said Andrei Panin, professor at the Moscow State University, Department of Geography, deputy director of the Institute of Geography of the Russian Academy of Sciences. According to the archaeologists, the construction had been going on for two summer seasons. And in 779 a coup occurred.
In the 770s, a ruler was in power, on the initiative of which the state went through a painful religious reform - the adoption of Manichaeism. In 779, an anti-Manichaean coup occurred, during which the ruler was killed. A comparison of this historical context and the exact dating of the construction radically changed the scientists' view of the purpose of the fortress.
“According to the information, it was suggested that the purpose of the complex was not defensive, as previously thought, but religious: it was a Manichaean monastery. If the monastery was built on the eve of the coup, then the previous rulers simply did not have time to use it, and the new ones no longer needed it. This explains the main mystery of Por-Bazhyn, the lack of traces of its use," said Andrey Panin.
The study of the exact age of Por-Bazhyn was the first example of the use of radiocarbon diagnostics of astrophysical events of the Middle Ages for the accurate dating of archaeological sites. In recent years, researchers from Japan, the USA and China have discovered at least two more “Miyake events” - in 994 AD and in 660 BC. Therefore, there is no doubt that the proposed method will be increasingly used both in archeology and in other sciences that study the history of society and the natural environment.