Facies and Stratigraphy of Upper Holocene Marine Event Deposit in Penghu, Chiayi, and Tainan Coasts

Typhoons and tsunami lash Taiwan frequently. It has been found challenging to evaluate coastal inundations and recurrence intervals of these events due to the lack of sufficient historical records, given that numerous systems of observation, forecast, mitigation, and prediction simulation have been established. Upper Holocene facies and stratigraphy of marine facies event deposit is one of the best solutions. Long-term geological records dating back to thousands of years ago are available for evaluating the event recurrence intervals. Facies characteristics, geochemistry, geophysics, and their variations of the event deposit reflect sedimentary erosion, transportation, and deposition during coastal marine flooding and are useful in reconstructing the inundation area, run-up, wave height, and post-event geomorphological and ecological change. The event deposit’s sedimentology and stratigraphy further provide important constraints on backward hydraulic simulation, geomorphological and ecological modeling, mitigation, and damage prevention and recovery. Origins of the ancient marine events may also be unveiled, such as the short-wavelength typhoon surge and the long-wavelength tsunami, and so the tsunami origins of an earthquake, volcanic eruption, and mass movement. Therefore, to establish the Upper Holocene marine event stratigraphy and sedimentology of Taiwan, the coastal areas spanning the southern Taiwan Strait are first selected in this project because of facing the mega-wave-prone Manila Subduction Zone and South China Sea. In three years, the project aims to accomplish field investigations of outcrop exposure and shallow excavation on the major islands of Penghu and along the Chiayi-Tainan coastlines and to comprehensively outline the regional history and future development of mega wave events in the studied area.