Coastal boulders related to extreme marine events impacting the ABC islands (Aruba, Bonaire, Curacao islands, Leeward Antilles)

Abstract

Extreme marine events determine different landform imprints, such as out-of-size deposits like coastal boulders with several tons in weight. These extreme marine events are usually connected to storms and tsunamis. Storms and tsunamis are characterized by a high-energy content, which is reflected in wave flow and wave height able to move the boulders. Several coastal boulders have been detected in Aruba, Bonaire, and Curacao (ABC) islands, overlying the marine terrace deposits that surround the seaward side of these islands. In this work, morpho-topographical surveys were performed on these coastal boulders in order to simulate the most probable events that caused their displacements. Unmanned Aerial Vehicle and close-range photogrammetry were used to reconstruct the volume and shape of boulders with their immersive scenario. Volume and shape of coastal boulders have been used to estimate the energy content able to determine their displacement. Furthermore, boulder samples were collected in order to assess their density and to obtain chronological constraints of the extreme marine events by applying U/Th and radiocarbon dating. Numerical models in Delft3D were applied to simulate the scenarios that could be responsible for the boulder movements. The results showed that the biggest boulders are located on Bonaire Island, located in the eastern part of the ABC archipelago, and were influenced by higher energy content than the Aruba and Curacao islands. This energy content could be related to three possible scenarios simulated in Delft3D: 1) a tsunami scenario connected to Venezuela earthquakes, 2) a Hurricane scenario impacting from the western side of the ABC archipelago, 3) a combination of multiple events (tsunami and storms) that caused differential boulders movement in the past.