Shelf-edge deglacial reef establishment and subsequent partial demise: Response to distinct pulses of sea-level rise associated with environmental changes

Abstract

The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m amplitude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is anchored in only two palaeo reefs (Barbados, Great Barrier Reef). Here, the authors present the analysis of a coralgal reef that thrived along the south-east Papua New Guinea Peninsula outer shelf during this initial pulse. In the cone of a piston core, a shallow Goniastrea retiformis coral colony was retrieved at 111 m below present sea-level and uranium/thorium dated to 19.4 ka BP. This colony had been buried beneath the debris of a proximal coralgal reef before its partial drowning at 14.5 ka BP. Seismic survey data suggest that the reef edifice was established directly on the eroded top of a lowstand shelf-edge delta, partially drowned and then back-stepped towards the south-east in response to three distinct deglacial sea-level pulses and stepwise increases of water column turbidity.