The role of compaction contrasts in sediments in decollement initiation in an accretionary prism

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doi: 10.1016/j.margeo.2011.02.011
Author(s): Raimbourg, Hugues; Ujiie, Kohtaro; Kopf, Achim J.; Hisamitsu, Toshio; Hamano, Yozo; Saito, Saneatsu; Kinoshita, Masataka
Author Affiliation(s): Primary:
JAMSTEC, Yokosuka, Japan
Other:
University of Orleans, France
MARUM, Germany
Kochi Core Center, Japan
University of Tsukuba, Japan
Volume Title: Marine Geology
Source: Marine Geology, 282(3-4), p.188-200. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. Includes appendices. 54 refs.; illus., incl. sketch map
Summary: To understand how decollements develop into the pristine sedimentary succession entering subduction zones, we have performed mechanical tests on samples from the sediment column entering the Nankai accretionary prism, Japan (ODP site 1173). Both poroelastic compliance and plastic shrinkage upon application of a large effective pressure sharply decrease with depth in a ∼100 m-thick domain in the upper section of the Lower Shikoku Basin unit, i.e. in a domain stratigraphically close to the actual location of the decollement near the toe of the prism. These property contrasts provide a potential explanation for the outward migration of the decollement into the incoming sediments. When approaching the deformation front, a given material particle is affected by an increase in stress, which has a component of vertical loading due to the deposition of overburden trench sediment, and also a component of lateral compression transmitted from the accretionary wedge. Depending on its initial mechanical state, the amount of lateral shortening in the incoming Nankai sediment column varies with depth and causes horizontal velocity gradients that concentrate into the mechanical transition zone (upper section of the Lower Shikoku Basin at appx. 450-550 m depth) into which the decollement eventually propagates. Future work has to assess the role of this plastic deformation relative to other governing factors such as friction coefficient and excess pore pressure, both at Nankai and along other active margins. Abstract Copyright (2011) Elsevier, B.V.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 16 Structural Geology; Accretionary wedges; Cementation; Compaction; Crust; Crustal shortening; Decollement; Diagenesis; Elasticity; Experimental studies; Laboratory studies; Leg 190; Leg 196; Marine sediments; Mechanical properties; Models; Nankai Trough; North Pacific; Northwest Pacific; ODP Site 1173; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Permeability; Pore pressure; Poroelasticity; Porosity; Sediments; Shear strength; Shikoku Basin; Spatial variations; Stress; Subduction zones; West Pacific
Coordinates: N321500 N321500 E1350200 E1350200
Record ID: 2011053909
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands