Distribution of resistive and conductive structures in Nankai accretionary wedge reveals contrasting stress paths

Marianne Conin and Sylvain Bourlange and Pierre Henry and Aurelien Boiselet and Philippe Gaillot. ( 2014 )
in: Tectonophysics, 611:0 (181 - 191)

Abstract

In this article, we study the characteristics and spatial distribution of the deformation structures along the Kumano transect of the Nankai accretionary wedge, and use this information to interpret the stress path followed by the sediments. Deformation structures are identified from logging while drilling (LWD) resistivity images of the materials surrounding the drill hole and from 3-dimensional X-ray CT-images of cores acquired during the IODP NanTroSEIZE project. The relative resistivity of the structures identified on logs and the strike, dip, and density of structures identified on CT scan images are measured. The analysis of dip and strike of structures indicates that most of the resistive structures identified on logging data correspond to compactive shear bands. Results also indicate that conductive structures predominate at the toe of the prism and above the main out of sequence thrust, in locations where past and recent erosion occurred. We propose several mechanisms that could explain the relation between erosion and the absence of compactive shear bands. We conclude that sediments followed different stress paths depending on their location within the wedge, and that those differences explain the distribution of deformation structures within the wedge. We also show the coexistence of dilatant and compactant structures in fault zones including the frontal thrust and mega splay fault, and we interpret the coexistence of these structures as a possible consequence of a transient fluid pressure.

Download / Links

BibTeX Reference

@ARTICLE{Conin2014181,
    author = { Conin, Marianne and Bourlange, Sylvain and Henry, Pierre and Boiselet, Aurelien and Gaillot, Philippe },
     title = { Distribution of resistive and conductive structures in Nankai accretionary wedge reveals contrasting stress paths },
   journal = { Tectonophysics },
    volume = { 611 },
    number = { 0 },
      year = { 2014 },
     pages = { 181 - 191 },
      issn = { 0040-1951 },
       url = { http://www.sciencedirect.com/science/article/pii/S0040195113006902 },
       doi = { 10.1016/j.tecto.2013.11.025 },
  abstract = { In this article, we study the characteristics and spatial distribution of the deformation structures along the Kumano transect of the Nankai accretionary wedge, and use this information to interpret the stress path followed by the sediments. Deformation structures are identified from logging while drilling (LWD) resistivity images of the materials surrounding the drill hole and from 3-dimensional X-ray CT-images of cores acquired during the IODP NanTroSEIZE project. The relative resistivity of the structures identified on logs and the strike, dip, and density of structures identified on CT scan images are measured. The analysis of dip and strike of structures indicates that most of the resistive structures identified on logging data correspond to compactive shear bands. Results also indicate that conductive structures predominate at the toe of the prism and above the main out of sequence thrust, in locations where past and recent erosion occurred. We propose several mechanisms that could explain the relation between erosion and the absence of compactive shear bands. We conclude that sediments followed different stress paths depending on their location within the wedge, and that those differences explain the distribution of deformation structures within the wedge. We also show the coexistence of dilatant and compactant structures in fault zones including the frontal thrust and mega splay fault, and we interpret the coexistence of these structures as a possible consequence of a transient fluid pressure. }
}