Coastal boulders emplaced by extreme wave events impacting the ABC islands (Aruba, Bonaire, Curaçao; Leeward Antilles, Caribbean)

Abstract

Large coastal boulders are ubiquitous geomorphological features that are emplaced along coasts by extreme marine events such as storms, hurricanes, and tsunamis. Many large coastal boulders have been identified on emergent fossil coral reefs on the windward sides of the Aruba, Bonaire, and Curaçao (ABC) islands in the Leeward Antilles of the Caribbean. Here, structure-from-motion/multi-view stereo techniques were used to map boulder sizes at several coastal sites in the ABC Islands as well as construct digital terrain models of the surrounding areas. Chronological constraints on boulder transport were established through the radiocarbon dating of the vermetids and coral colonies that comprised boulders located along a ridge on Aruba Island. A suite of hydrodynamic models was used to empirically derive the required flow thresholds for boulder displacement to determine whether tsunamis or hurricanes were responsible for detaching and transporting these boulders. Our results suggest that multiple tsunamis, most likely triggered by the El Pilar fault, located near the Venezuelan coast, were the cause of boulder detachment and transport in this region during the Holocene, between 4000 and 500 years BP.