Potential for timing high-energy marine inundation events in the recent geological past through age-dating of reef boulders in Fiji

International audienceTransported coastal boulders have increasingly come to represent a valuable element of investigations within the broader framework of multi-proxy approaches applied to coastal hazard studies. Through a case study on Taveuni Island in Fiji, this paper outlines some approaches and hindrances to effective timing of prehistorical high-energy marine inundation events (storms and tsunamis) on tropical coastlines from the evidence of reef-platform carbonate boulders. Various sources of errors are outlined that investigators must consider when attempting to use carbonate boulder ages as a surrogate for timing past events. On Taveuni, uranium : thorium dates with a high level of precision (1–7 years) suggest that major inundation events have a return period of approximately 40–45 years since 1650 AD. Of particular importance, considerably different age dates are provided by coral samples sourced from the top and bottom (i.e. opposite faces) of individual boulders, so highlighting interpretation biases that must be avoided