Journal of Geology & Geophysics
Open Access

Potential paleotsunami records as deduced from coral boulders on the lanyu island, Southeastern Taiwan

International Conference on Geology

June 22-23, 2015 Florida, USA

Yoko Ota and J B H Shyu

Posters-Accepted Abstracts: J Geol Geosci

Abstract :

In the last decades, several disastrous tsunamis hit a large area of coastal Asia and produced numerous casualties and economic losses. Taiwan is in urgent need for more knowledge of past tsunami records and potential tsunami genetic source. However, in Taiwan, paleotsunami was not studied until recently, even though many geological evidences of paleotsunami have been found in the Ryukyu Islands close to Taiwan. We expect that the east coast of Taiwan has a large potential for paleotsunami research. We provide evidence from our recent results from the coast of Lanyu offshore southeastern Taiwan. On the basis of detailed geomorphic mapping and field observation, we identified six sites in the northern part of the Lanyu where nine large coral boulders rest on Holocene coral terraces. We mapped their location and measured their profiles and took samples for 14C and U series dating. All the boulders likely moved by extremely strong waves and four sites have better constraints to suggest that the boulders may be transported during paleotsunami event based on large size and their occurrence. The age of the boulders range from 100 to 200 year ago to ca.7000 yBP suggest that the extremely strong wave events occurred at least several times since the middle Holocene and the youngest event may correlate with the 1771 Meiwa tsunami of the southern Ryukyu or alternatively undocumented event along the eastern coast of Taiwan. The location of coral boulder sites suggests that the sources of the events are located to the north of the island.