Magnetic fabrics of deformed soft sediments at the deformation front of the Hikurangi subduction margin

Online Access: Get full text
Author(s): Greve, Annika; Kanamatsu, Toshiya; Fagereng, Ake; Morgan, Julia; Wang Maomao; Savage, Heather M.; Kars, Myriam Annie Claire; Li, Xuesen; Wallace, Laura M.; Saffer, Demian M.; Petronotis, Katerina E.
International Ocean Discovery Program (IODP), Expedition 372 Scientists, College Station, TX
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
University of Cape Town, South Africa
Rice University, United States
Hohai University, China
Lamont-Doherty Earth Observatory, United States
Kochi University, Japan
University of Bremen, Germany
University of Texas at Austin, United States
Pennsylvania State University, United States
International Ocean Discovery Program, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Site U1518 of International Ocean Drilling Program Expedition 375 penetrated approximately 500 m of Pleistocene aged mud- and siltstones in the outer accretionary wedge, near the deformation front of the Hikurangi subduction margin. The top of a splay fault zone was penetrated at ca. 300 mbsf, followed by an approximately 60 m thick zone of variable deformation intensity that shows both brittle and ductile deformation features. This zone can be divided into an upper main fault, a basal subsidiary fault, and an intervening zone of lower intensity deformation. Diagnostic rock magnetic parameters measured on core-samples suggest pervasive mineral diagenesis, as indicated by the presence of authigenic greigite. Here we aim to quantify the style of sediment deformation from hanging wall, footwall, and throughout the fault zone based on the magnetic strain ellipsoid. Anisotropy of magnetic susceptibility, measured on over 300 discrete samples, indicate that the entire sequence is dominated by bedding parallel oblate fabric. The corrected degree of anisotropy P' increases slightly with depth (1.01<P'<1.08), which is typical for foliation by lithostatic compaction. Samples from the bottom sequence of the hanging wall and from within the main and subsidiary fault zones yield a wider distribution of P', the shape parameter T and the magnetic lineation (L) than the surrounding lithologies, most likely reflecting variable degrees of strain. Magnetic remanence directions enable the reorientation of the AMS tensor into a geographic reference frame. Implied deformation directions will be discussed and our results compared to previous studies in the Kumano basin area of the Nankai Trough, SW Japan.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 18 Geophysics, Solid-Earth; Authigenic minerals; Deformation; Expedition 375; Greigite; Hikurangi Margin; IODP Site U1518; International Ocean Discovery Program; Magnetic properties; Pacific Ocean; Plate tectonics; South Pacific; Southwest Pacific; Subduction; Subduction zones; Sulfides; West Pacific
Coordinates: S385133 S385133 E1785346 E1785346
Record ID: 2019050436
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States