Sedimentary evidence of tsunamis in New Caledonia, southwest Pacific

Abstract

This study aims to identify tsunamis in the coastal sedimentary archives of New Caledonia (Grande Terre and the Loyalty Islands) in the southwest Pacific, to extend a relatively short historical tsunami record (150 years), and to bring more constraints on the frequency of the main tsunamigenic earthquakes in the region. Using a combination of sedimentary and geochemical approaches on sediment core samples, we document three types of deposits related to marine inundation: (1) bioclastic sand layers; (2) crypto-deposits with a marine chemical signature; and (3) accumulations of rounded pumice lapilli. Most of the sampling sites being located outside the morpho-dynamic impact zone of the cyclones, a tsunami origin is preferred. The spatial distribution of the deposits suggests tsunami runups exceeding 2.5 m a.s.l. on the northeastern coast of Grande Terre, 6 m on the eastern coast of Maré Island, and 10 m on the northeastern coast of Lifou Island. Finally, at least six tsunamis were preserved in the sedimentary record: one event soon after 1000 BCE, two events during the first millennium CE, and at least three events during the last millenium (including a 15th century tsunami, the 28 March 1875 tsunami, and a tsunami possibly related to the 1729 earthquake in Vanuatu).