[U-03] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U03-05] Uncover a world-unique ancient ruin of Nan Madol, the Venice of the Pacific

★Invited Papers

*Chuan-Chou Shen^1,2、Felicia Beardsley³、Shou-Yeh Gong⁴、Osamu Kataoka⁵、Minoru Yoneda⁶、Yusuke Yokoyama⁶、Albert Yu-Min Lin⁷ (1.High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University、2.Research Center for Future Earth, National Taiwan University、3.University of La Verne、4.National Museum of Natural Science, Taichung, Taiwan ROC、5.Sophia University、6.The University of Tokyo、7.University of California, San Diego)

キーワード：Nan Madol, Saudeleur Dynasty, Coral, U-Th dating

Astonishing ancient architectures were made widespread in the Pacific. However, most of the construction histories remain uncertain due to the lack of developed writing system and the limitation of dating techniques. World-unique Nan Madol (0.7 km in width and 1.5 km in length), a ruined city called the “Venice of the Pacific” with over 100 artificial islets, on the southeastern coast of island Pohnpei in Micronesia were built with basalt megaliths and scleractinian coral cobbles. The main construction of Nan Madol of Pohnpei could range anywhere from the 13th-or-14th to the 16th-17th centuries, associated with the rise and fall of the Saudeleur Dynasty. However, the timing of its construction, along with the rise and fall of the dynasty, has remained unresolved. Our team used high-precision U-Th dating techniques to date the selected pristine coral infills and reveal the construction time. With over 150 coral ages determined, results show a peak in activity of Nan Madol construction during the mid 11th century could be associated with the rise of the dynasty. In the early 15th century, construction activities ceased, most likely associated with the dynasty’s downfall. Both Nan Madol construction and the rise and fall of the dynasty occurred 2-3 centuries earlier than previously estimated, which brackets their development between periods dominated by El Niño-Southern Oscillation (ENSO) variability and tectonic-related sea level rise. With the current intensification of ENSO variability and sea level rise, the coming decades will likely experience the inundation of more islands and an increase in the numbers of climate refugees.