Dynamic as always – Sedimentary evolution of a coral reef island from the Spermonde Archipelago, Indonesia

The effects of changing climate and environmental conditions on coral reef islands have received a lot of attention, and the findings are discussed broadly. The low elevation of such islands above mean sea level and the largely unconsolidated sediment is exposing them to hydrodynamic processes. Coral reef islands are formed by sediment sourced from the surrounding reef systems and depend on these reef systems as continuous material suppliers. Shifts in these governing conditions may affect these landforms, however the results of such shifts remain controversial as island-response is likely to be regionally specific. The present sedimentological study addresses the formation of a reef island in the Spermonde Archipelago, Sulawesi, and its development through time. Sediment cores of 10 m length taken on the island allowed to reconstruct the sedimentary history of this mid-shelf island. The carbonate facies from these cores reflects the development of the island and thus allows for inferring the evolution of the surrounding ecosystem as well as the hydrodynamic regime that governed sedimentation. While sediment from the maximum depth of the cores mirror parautochthonous accumulation in a lagoonal environment, subsequent sedimentation is thought to be the result of hydrodynamic events with oscillating intensity.