Paleosea-Level Records from Late Quaternary Coral Reef Terraces on Araki Island, Vanuatu; Comparison With Previous Results from Huon Peninsula, Papua New Guinea

New 230Th/238U ages for precisely leveled fossil corals from Araki Island, Vanuatu, generally corroborate MIS 3 and 4 paleosealevel estimates from the Huon Peninsula (HP), Papua New Guinea. Corals have been essential for paleosea-level reconstructions and their timing because they provide such precise U-series dates. However, paleosea-level estimates from uplifted corals rely on inferring tectonic uplift rates in order to subtract them from coral elevations. Uplifted coral reefs at central Varnuatu and Western Solomons exemplify the extremely abrupt tectonic rate changes that forearcs can undergo. If uplift rate changes are not detected and taken into account then paleosea level estimates could be wrong by tens of meters. Araki Island, located 2500 km and two plates away from the Huon Peninsula is tectonically independent. Araki should share a similar paleosea level history with HP, including Global Isostatic Adjustments, and other water-loading influences, but should be tectonically different. Assumptions similar to those used to infer HP sea-level estimates are applied for the Araki mid-Holocene, MIS 5c, and MIS 5e paleosealevels in order to constrain MIS 3 and 4 paleosea levels. Before and during MIS 5e (~130-120 ka) until MIS 5c (~106 ka) Araki subsided at ~3 mm/yr. At or soon after 106 ka Araki abruptly began uplifting at a mean rate of ~1.65 mm/yr. This ~1.65 mm/yr mean uplift rate appears to have prevailed until ~25-30 ka after which uplift accelerated to a mean rate of ~4.6 mm/yr. These uplift rates imply MIS 3 and 4 paleosea levels very similar to those inferred from the HP reef terraces of similar ages. The abrupt changes in vertical tectonics that our coral ages and elevations imply for Araki Island offer insightsregarding the remarkably rapid tectonic variability and possible mechanisms that control convergent margin tectonics as well as the challenges involved in using the data for paleosea level reconstructions.