Geological records of South China Sea tsunamis on Penghu Islands, Taiwan

•Three layers of tsunami deposits were first identified on Penghu Islands, Taiwan.•Embedded in terrestrial deposits, the layers are rich in beach gravels and shells.•We devise a systematic method to classify the likelihood of tsunami deposits.•Carbon-14 ages of the layers are from AD 300 to 500, 1000 to 1100, and 1400 to 1500.•The middle layer may be related to the AD 1076 Guangzhou tsunami of comparable age.