Eustatic sea-level change of 11 - 5 ka in Western Taiwan, constrained by radiocarbon dates of core sediments

Abstract

Twenty-nine cores and two outcrops in the Western Coastal Plain, each containing more than one radiocarbon date (5 - 20 ka; totally 74 dates), are used to determine the 11 - 5 ka eustatic sea level in Taiwan. All the dates are obtained from coastal sediments with deposition positions assumed ±3 m of the sea level. These dates can be used to calculate rock uplift (subsidence) rates for given eustatic sea-level data. The sea level data derived from Penghu (< 5 ka) and the Sunda Shelf (> 11 ka) are applied, and the rock uplift of the study sites is assumed to be steady over time. The 11 - 5 ka sea level is constructed by repetition of changing its shape until the dates in the same cores yield consistent rock-uplift rates. Optimal sea-level curves are found to fit all but seven dates used. These sea-level curves are characterized by: (1) a rapid rise (> 13 m ky-1) around 11 - 10 ka; (2) a rise of 8 - 9 m ky-1 from ∼10 ka to 6.5 - 6.6 ka when the sea level approached the modern level, and (3) a much slower rise after 6.5 - 6.6 ka.