Linking sedimentary imprints of storms and tsunamis with numerical wave modeling: A case from a coastal lagoon in the Lesser Antilles (Saint Martin)

Abstract

We examined sedimentary records in a coastal lagoon on Saint Martin Island in the Lesser Antilles to identify and characterize extreme-wave events (EWEs), such as hurricanes and tsunamis. Employing a comprehensive approach involving sedimentological, geochemical, and radiocarbon dating analyses, complemented by X-ray computed microtomography (micro-CT) for examining sediment fabrics, we applied this multiproxy method to three oriented short sediment cores along a transect. This allowed us to identify sediment layers linked to both tsunami- and hurricane-induced EWEs. Five out of the seven EWEs were identified as paleo-tsunamis through their geochemical, sedimentary, and structural signatures. These five paleotsunamis were successfully dated over the last 3500 years, including the well-documented Pre-Columbian tsunami at approximately 1400 yrs CE and the transatlantic Lisbon tsunami at 1755 CE. This suggests a tentative local tsunami chronology of five well-documented events over the last 3500 years with a recurrence interval of 400 to 500 years. However, the most recent EWE corresponded to the powerful Category 5 Hurricane Irma in 2017. Over the last 150 years, another 14 less intense hurricanes impacted the island, leaving no sediment imprints in the lagoon. This finding is in line with most recent publications showing that tropical storm intensification rates have already changed as anthropogenic greenhouse gas emissions have warmed the globe (Garner, 2023). Furthermore, micro-CT-based sediment analysis provided a deeper understanding of the relationship between sediment fabric and tsunami wave dynamics. Therefore, we used the deposits of the Pre-Columbian tsunami and compared paleo-flow directions from micro-CT-derived fabric patterns to those from numerical tsunami models. The results that best explain the Pre-Columbian tsunami deposit emplacement are in line with a Mw 8.5–8.7 megathrust earthquake source located on the subduction interface at the Puerto Rico Trench, north of Anegada Island (Cordrie et al., 2022). Ultimately, integrating deposits of EWEs with numerical models is pivotal for devising effective hazard mitigation strategies tailored to vulnerable coastal communities. Cordrie, L., Feuillet, N., Gailler, A., Biguenet, M., Chaumillon, E., Sabatier, P., 2022. A Megathrust earthquake as source of a Pre-Colombian tsunami in Lesser Antilles: Insight from sediment deposits and tsunami modeling. Earth Sci Rev 228, 104018. https://doi.org/10.1016/j.earscirev.2022.104018 Garner, A.J. Observed increases in North Atlantic tropical cyclone peak intensification rates. Sci Rep 13, 16299 (2023). https://doi.org/10.1038/s41598-023-42669-y