Impact of environmental parameters on coral reef development and drowning: Forward modelling of the last deglacial reefs from Tahiti (French Polynesia; IODP Expedition #310)



The sedimentological and chronological analysis of the last deglacial reef sequences of Tahiti (French Polynesia), drilled during the Integrated Ocean Drilling Program Expedition 310, provide a high-resolution data set allowing a well-constrained forward modelling study. This study represents the first attempt to model in three dimensions the coral reef development of Tahiti during the last deglacial sea-level rise (23 000 to 6000 cal yr bp) using the software dionisos developed by IFP Energies nouvelles. It allows the testing of the reconstructed last deglacial sea-level curve and the different environmental parameters (for example, wave energy and sediment fluxes) that could have influenced the reef development. These last deglacial reef sequences form two prominent ridges occurring seaward of the living barrier reef that consist of successive submerged reefs. These reefs have been prone to drowning because the window of maximum carbonate production rate is inhibited by high water turbidity (sediment supply from a nearby river), shallow depth of wave action and substrate availability. These factors, combined with rapid sea-level rise, have driven the growth of retrograding reef pinnacles. Local factors (substratum nature, sediment supply and wave energy) were the main processes that induced the drowning of the inner ridge, whereas interplay of local and global factors (acceleration of the sea-level rise) was responsible for the drowning of the outer ridge. This particular acceleration of sea-level rise of 16 m between 14·6 ka and 14 ka bp corresponds to meltwater pulse 1A.