Paleogeography and volcanic morphology reconstruction of a buried monogenetic volcanic field (part 2)

Abstract

Over the last two decades, a growing number of studies have identified the presence of ancient volcanic systems buried and preserved within sedimentary basins. Continuous improvements in remote-sensing techniques such as seismic reflection offer an opportunity to analyze how these extinct buried volcanoes have formed and evolved. In this paper, we reveal the Maahunui Volcanic Field (MVF), a cluster of middle Miocene volcanoes and shallow intrusions currently buried by more than 1000 m of sedimentary strata of the Canterbury Basin, New Zealand. This “fossil” volcanic field is imaged by high-quality 2D seismic lines and has representative igneous rocks penetrated by the Resolution-1 borehole. These data have been used to reconstruct the original morphology of the volcanoes and the regional paleogeography in which eruptions and shallow ( 200 m) located in a neritic setting were possibly emergent at the paleosea surface, forming an archipelago of nine small extinct volcanic islands. This study demonstrates the value of detailed seismic reflection mapping and borehole analysis for improving understanding of the processes that formed, transformed, and preserved ancient volcanoes now buried in sedimentary basins.