Tectonics of the Central New Hebrides Arc, North Aoba Basin

Abstract

Drilling at Sites 832 and 833 in the North Aoba Basin provided the first continuous section in the central New Hebrides Island Arc from the Late Miocene. We report here tectonic structures observed in the cores and data obtained from the boreholes with the Formation MicroScanner logging tool. The structures observed on cores were geographically oriented using the declination of the natural remanent magnetism obtained from continuous core sections and from discrete samples. The corrected data are generally in good agreement with in-situ Formation MicroScanner measurements, indicating the reliability of the reorientation method that assumes that no tectonic rotation occurred since the deposition of the sediments. Finally, structural data allow us to obtain information concerning the deformations, especially the direction of sequence tilting and the orientations of principal stress axes. Using also the lithostratigraphy, we reconstruct the late Miocene to Pleistocene tectonic history recorded in the North Aoba Basin and attempt to correlate these data with the onshore geology in the context of the New Hebrides Island Arc-d'Entrecasteaux Zone collision.