Control of paleoshorelines by trench forebulge uplift, Loyalty Islands

The Loyalty Islands, part of the UNESCO World Heritage Site Lagoons of New Caledonia, exhibit unique paleoshoreline features shaped by neotectonic uplift. Unlike most tropical Pacific islands, these islands formed due to the uplift of pre-existing atolls on the flexural forebulge of the New Hebrides Trench. The study reveals that island morphology and topography vary with distance from the trench crest, influencing emergent paleoatolls like Maré and Lifou, which display ancient barrier reefs forming high-standing annular ridges around interior plateaus representing paleolagoon floors. Ouvea's partially emergent rim flanks a drowned lagoon, showcasing diverse paleoshoreline features such as paleoreef flats and tidal notches. These features record uplift rates since the last interglacial and mid-Holocene sea-level highstands, aligning with theoretical predictions based on trench subduction rates. The research highlights the Loyalty Islands as a case study for neotectonically controlled island environments.

Dickinson, W. R. (2013). Control of paleoshorelines by trench forebulge uplift, Loyalty Islands. Quaternary Research, 80(1), 125–137. https://doi.org/10.1016/j.yqres.2013.04.007