Continuous reef growth during the last 23 cal kyr BP in a tectonically active zone (Vanuatu, SouthWest Pacific)

Abstract

At Urélapa island, Vanuatu, sea-level rise and a tectonic uplift of ∼3 mm yr −1 have controlled water depth and the colonization and reef development on a substrate from 23 until 6 cal kyr BP. Analysis of coralgal assemblages offers insights on the mode of reef growth and on water depth over the reef for the studied period. Those assemblages, precisely dated by the 230Th/ 234U method, give valuable information on the rate and timing of sea-level rise since the Last Glacial Maximum. The Urélapa reef sequences are characterized by upwards replacement of reef frameworks which indicates changes in wave energy through time. The sudden acceleration of sea-level rise associated with meltwater pulse-1B at around 11.3 cal kyr BP is marked by a change in reef growth strategy, from a keep-up mode to a catch-up mode. We examine the delay in timing of the occurrence of suitable substrates, the role of paleoceanographic factors and the influence of possible jumps in sea level.