An abrupt backreef infilling in a Holocene reef, Paraoir, Northwestern Luzon, Philippines

Shou Yeh Gong, Tso Ren Wu, Fernando P. Siringan, Ke Lin, Chuan Chou Shen

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We describe a sudden backreef infilling at the west coast of Luzon, Philippines, which occurred after 324 ± 12 yr ago (year BP, before 1950 AD). Results of 30 230Th-dated fossil corals from the surface and 5 cores, 17-29. 1 m in length, recovered from a Holocene reef at Paraoir show that the reef flat developed in two stages. The reef margin is dated at 10,256 ± 50 (2σ) yr BP at 23. 9 m below mean sea level (MSL) and about 6,654 ± 29 yr BP at 3. 7 m below MSL with ages increasing with depth. The reef flat was formed with sediments of 818-324 yr BP old, which do not follow an age-depth correlation. The evidence suggests that a backreef moat remained empty throughout the buildup of the reef for about 6 kyr and was filled abruptly with a 26-m-thick succession of rubble and bioclastics by an extreme wave event (EWE) after 324 ± 12 yr BP. Field evidence, historical records, and tsunami simulation suggest the EWE sedimentation was likely caused by a single severe tropical cyclone, although the possibility of tsunami is not ruled out. The Paraoir reef flat was built up in a mode different from previously reported cases of Holocene reefs.

Original languageEnglish
Pages (from-to)293-303
Number of pages11
JournalCoral Reefs
Issue number1
StatePublished - Mar 2013


  • Backreef infilling
  • Coral U-Th dating
  • Extreme wave event
  • Holocene reef
  • Philippines
  • Tropical cyclone


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