Sedimentary records of extreme wave events in the southwestern Caribbean

High-energy events in the Caribbean Sea include hurricanes, tropical storms, cold fronts and tsunamis. El Rosario Archipelago, located on the Colombian Caribbean shelf (SW Caribbean) consists of a set of ancient and successive coralline formations, uplifted by tectonic and diapiric activity. We undertook an integrated analysis of instrumental climate records and sediment records from a beach ridge system, a reef lagoon and a mangrove lagoon in the Archipelago, to determine whether historical extreme weather events influenced the coastal geomorphology and reef sedimentation. Statistical analysis of historical extreme winds and waves was accomplished using ERA-Interim reanalysis data. Extreme sea-level events were identified with calibrated data from the nearest tide gauge. Sediments from the reef and mangrove lagoon were dated using 210Pb and 14C. Beach ridges were dated indirectly thorough their relationship with the closure of the mangrove lagoon. The eroding capacity of the historical extreme waves (i.e. maximum grain size that could be entrained by the orbital velocity of the waves) was compared with the grain sizes present in the deposits, and foraminifera species helped to determine the provenance of those deposits. Storms typically occur during the dry season associated with cold fronts. Foraminifera and coral fragments indicated that beach ridges were supplied with sediment that eroded from ancient terraces. In the reef lagoon, a 56-cm-thick unit of coarse coral and shell debris, grading to a finer sediment, represents a major high-energy event that occurred after ca. 1655 CE. This event was also recorded by the beach ridges. The probable explanation for this high energy unit is that a strong event carried coarse sediments into the lagoon, with subsequent reworking by minor events, such as those reported in the historical record. Two tsunamis occurred in the Caribbean after 1655, but the associated waves reaching the area were not strong enough to deposit the coarser clasts of the unit. Thus, coarser material was probably delivered to the lagoon as a consequence of sudden diapiric and/or tectonic activity. Our data show that major storms and other high-wind, extreme-wave events shape the beach ridges on Rosario Island, every 70 years. The findings suggest that if global climate change increases the frequency and/or magnitude of major storms and other high-wind, extreme wave events that impact the Caribbean coast of Colombia, then El Rosario Archipelago will be susceptible to future, significant landscape transformations.