A multiproxy analysis of extreme wave deposits in a tropical coastal lagoon in Jamaica, West Indies

摘要

The Small Island Developing States (SIDS) of the Caribbean Region are vulnerable to natural hazards including earthquakes, tsunamis and tropical cyclones that can cause widespread devastation. Sedimentary archives of these hazards are often well-preserved in coastal lagoons; however, few studies in the Caribbean have adopted a multiproxy approach to their reconstruction. Here, we present a 1200-year multiproxy record of extreme washover events deposited within a coastal mangrove lagoon on the south coast of Jamaica. Manatee Bay lagoon is a permanent fresh-brackish-water mangrove lagoon separated from the Caribbean Sea by a low-elevation carbonate beach. Fifteen sediment cores recovered along five shore-normal transects contain ostracod-rich authigenic carbonate lake muds interspersed with beds of organic lake mud and mangrove peat. The cores contain evidence of multiple palaeo-washover deposits that are readily distinguished by their sedimentology, geochemistry and microfossil assemblages. Hypersaline conditions dominated the early part of the record (similar to 800 to 900 CE), and we infer a freshening of lagoonal waters and the subsequent expansion of the mangrove community following an extreme wave event that occurred some time before similar to 1290 to 1400 CE. We constrain the primary historical-washover deposit to 1810-1924 CE (2 sigma; 71% probability), a period characterised by extreme tectonic and meteorological events, which include the Great Kingston Earthquake of 1907 and a local episode of enhanced hurricane activity. Whilst the balance of circumstantial evidence indicates that the deposit was probably emplaced during the tsunami generated by the 1907 earthquake, we are currently unable to differentiate between tectonically and meteorologically driven washover events based on their sedimentological characteristics.