Mid- to late Holocene environmental and climatic changes in New Caledonia, southwest tropical Pacific, inferred from the littoral plain Gouaro-Déva |
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| Authors: | Denis Wirrmann Anne-Marie Sémah Jean-Pierre Debenay Magali Chacornac-Rault |
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| Institution: | aCentre IRD France Nord, Unité 182, Paléoproxus, Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques, LOCEAN UMR 7159 (IRD/CNRS/UPMC/MNHN) - Institut Pierre-Simon Laplace, 32 Avenue Henri Varagnat, 93143 Bondy cedex, France;bInstitut de recherche pour le développement (IRD), UR PALÉOTROPIQUE, BP A5, 98848 Nouméa cedex, Nouvelle-Calédonie;cDpt. de Préhistoire, Muséum national d'histoire naturelle, (MNHN) UMR 7194, USM 204, 1 rue René Panhard, 75013 Paris, France |
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| Abstract: | Multiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings, emersion or very high-energy conditions, likely related to climatic changes and mostly controlled by ENSO variability. Between 2750 and 2000 cal yr BP, relatively dry and cool climate prevailed, while wetter conditions predominated between ca. 1800 and 900 cal yr BP. The Rhizophoraceae peak between ca. 1080 and 750 cal yr BP, coeval with the MWP, may indicate a global phenomenon. Microcharcoal particles present throughout the record increased after 1500 cal yr BP, suggesting an anthropogenic source. From ca. 750 cal yr BP the appearance of current type of vegetation marks the human impact. |
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| Keywords: | New Caledonia Littoral swamp Holocene Relative sea level ENSO Medieval Warm Period Extreme event Sedimentology Foraminifera Pollen |
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