Sea level reconstructions from stable and moved Pacific Islands: Marquesas, Vanuatu, New Caledonia   Email     Print   PDF

Norbert Frank¹, Guy Cabioch², Lucien Montaggioni³, Eline Sallé1, Claire Seard⁴, Martine Paterne¹, Christophe Colin⁵

¹LSCE, unité mixte CEA-CNRS-USVQ, Gif-sur-Yvette, France

²IRD, Unité de Recherche “Paléotropique”, Nouméa, New Caledonia

³LGC, Université de Provence, Marseille, France

⁴CEREGE, Aix-en-Provence, France

⁵IDES, Université de Paris Sud, Orsay, France

Bathymetric surveys of submarine platforms and terraces of the tropical Marquesas archipelago (French Polynesia), coupled with sedimentological and paleoecological analyses reveal the occurrence of distinct intervals of reef deposition during the last deglacial sea-level rise (i.e. the last 26,000 yr or 26 ky). The observed replacement of shallower habitats by deeper ones is interpreted as an upward-deepening sequence. Identification of morphological and biological features combined with coral dating provide evidence of 4 reef generations (RG) between 26 and 9 ka, now ranging from 138 to 58 m in depth. Their development was probably interrupted by abrupt rises in sea-level and/or drastic climate changes. Such a scenario is similar to observations reported in Barbados and Hawai'i where rapid rises in sea-level, interpreted as reflecting major melting events of continental ice, caused the drowning of reefs. In contrast to the glacial/interglacial sea level recorded from the tectonically almost stable Marquesas, New Caledonia is due to its slow subsidence a place to trace solely sea level high stands and flooding levels. Reef tracks are easily identified and coring, subsequent coral dating and habitat investigation provides good constrains on past sea level highs during marine Isotope Stage 1, 5, 7, 9 and likely beyond. But how can we close the gaps between sea level low and high recordings in the western Pacific?

Since a decade the today rapidly uplifting Island Vanuatu has been studied and exposed coral reef where dated. However, the unique tectonic history of the past 400ka may now provide the possibility to close the gaps of the Pacific sea level history since stage 7 till present.