Abstract
Near-seafloor bathymetric and magnetic data have been collected by Autonomous Underwater Vehicle (AUV) and manned submersible (DSS) over a volcanically active area southeast of Futuna Island, French Territory of Wallis-and-Futuna, in the Southwestern Pacific Ocean. Located at the edge of the Lau and North Fiji basins, at the convergence of the Pacific and Australian plates, this area is characterized by intense volcanic and tectonic activity. Direct observation by submersible reveals that the seafloor is covered by recent lava flows, volcanoes and large, active or inactive calderas filled by smooth lava flows and eventually hosting hydrothermal sites. We investigate the volcanic chronology by combining a Bayesian inversion of the AUV-gridded magnetic data with an inversion of the submersible data specifically designed to estimate the rock magnetic polarity and absolute magnetization. We show that some volcanoes predate the last (Brunhes-Matuyama) magnetic polarity reversal 780 kyr ago whereas their neighbors exhibit a normal polarity and appear to be recent. This result suggests that the seafloor in this region has undergone continuous and sparse volcanic activity over the last few million years.
Highlights
The most active volcanic area in the world, known as the Pacific Ring of Fire, encompasses the Pacific Ocean and marks the limits of the Pacific Plate
Combining a Bayesian inversion of the AUVgridded magnetic data (Honsho et al, 2012) with an inversion of the submersible data designed to estimate the rock magnetic polarity and absolute magnetization (Szitkar et al, 2015a), we show that the volcanic activity started before the last magnetic polarity reversal (780 ka) and has been continuous ever since, with no signs of waning
Ship-based bathymetric data collected during campaigns FUTUNA 1 and 3 contribute to refine this model and allow precising the plate contours, in the vicinity of Futuna Island with the definition of new micro-plates
Summary
The most active volcanic area in the world, known as the Pacific Ring of Fire, encompasses the Pacific Ocean and marks the limits of the Pacific Plate. Combining a Bayesian inversion of the AUVgridded magnetic data (Honsho et al, 2012) with an inversion of the submersible data designed to estimate the rock magnetic polarity and absolute magnetization (Szitkar et al, 2015a), we show that the volcanic activity started before the last magnetic polarity reversal (780 ka) and has been continuous ever since, with no signs of waning Such “intraplate” (i.e. off the well-defined plate boundaries) volcanic activity may result from melting of the underlying Indian ocean-type mantle and an additional input driven by the Samoa hotspot (Jackson et al, 2010; Jenner et al, 2012).
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