Timing of tectonic uplift rate change at Araki, Vanuatu, derived from 230-Th dating of fossil corals

Abstract

New data from precisely leveled and 230-Th-dated coral fossils allow for better constraints on the recent (~125 ka) tectonic history of Araki, Vanuatu. Subduction of two large underwater landforms have caused significant deformation to the intraoceanic arc on which Araki is centered and induced a variable and complex tectonic history. Due to the relatively few intraoceanic arcs undergoing similar collisions, an effort to better constrain and understand the tectonic history of Araki is valuable. This study presents an uplift model that builds on previous constraints of the tectonic history of Araki using fossil coral elevation and age data and a reference sea level curve. Data from fifty-nine samples was collected and used to provide chronological constraints for paleo shorelines that in turn offered insight into the tectonic history. The model suggests subsidence at a rate of 3.9 mm/yr from 125 ka to 106 ka, a shift to uplift at 106 ka continuing at a rate of 1.4 to 1.6 mm/yr until 25 – 30 ka, and then increasing to a rate of 4.6 mm/yr until the present. The abrupt changes in vertical tectonics implied by this modeling offers insight into the rapid tectonic variability and possible mechanisms controlling convergent margin tectonics.