Porosity loss within the underthrust sediments of the Nankai accretionary complex; implications for overpressures

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doi: 10.1130/0091-7613(2002)030<0019:PLWTUS>2.0.CO;2
Author(s): Screaton, Elizabeth; Saffer, Demian; Henry, Pierre; Hunze, Sabine; Moore, Gregory F.; Taira, Asahiko; Klaus, Adam; Becker, Keir; Becker, Luann; Boeckel, Babette; Cragg, Barry A.; Dean, Allison; Fergusson, Christopher L.; Hirano, Satoshi; Hisamitsu, Toshio; Kastner, Miriam; Maltman, Alex J.; Morgan, Julia K.; Murakami, Yuki; Sánchez-Gómez, Mario; Smith, David C.; Spivack, Arthur J.; Steurer, Joan; Tobin, Harold J.; Ujiie, Kohtaro; Underwood, Michael B.; Wilson, Moyra
Ocean Drilling Program, Leg 190, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
University of Florida, Department of Geological Sciences, Gainesville, FL, United States
University of Wyoming, United States
École Normale Supérieure, France
Geowissenschaftliche Gemeinschaftsaufgaben, Federal Republic of Germany
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 30(1), p.19-22. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 15 refs.; illus., incl. sect., sketch map
Summary: Subduction complexes provide an opportunity to examine the interactions of deformation and fluid flow in an active setting. Ocean Drilling Program Leg 190 investigated the relationship between deformation, physical properties, and fluid flow in the toe of the Nankai Trough accretionary complex. With three sites (two from Leg 190, one from a previous leg) penetrating the decollement zone at various stages of development along the same transect, it is now possible to examine the change in porosity during rapid loading by trench turbidites and subsequent underthrusting. Results indicate inhibited dewatering and probable overpressure development seaward of the frontal thrust. Comparison of a reference site porosity versus depth curve to data from a site located within the protothrust zone indicates an overpressure ratio, λ*, of ∼0.42, where λ* = [(pore pressure - hydrostatic pressure)/(lithostatic pressure - hydrostatic pressure)]. These overpressures suggest that the hemipelagic sediments have insufficient permeability for fluid escape to keep pace with the rapid loading by turbidite deposition within the trench. At a site 1.75 km farther arcward, an excess pore pressure ratio of λ* = ∼0.47 was estimated, reflecting the additional loading due to recent thickening by the frontal thrust.
Year of Publication: 2002
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Compaction; Decollement; Deformation; Faults; Fluid dynamics; Hemipelagic environment; Leg 131; Leg 132; Leg 190; Marine environment; Marine sediments; Nankai Trough; North Pacific; Northwest Pacific; ODP Site 1173; ODP Site 1174; ODP Site 808; Ocean Drilling Program; Overpressure; Pacific Ocean; Permeability; Physical properties; Plate tectonics; Pore pressure; Porosity; Sediments; Shikoku Basin; Subduction; Thrust faults; Troughs; Turbidite; Underthrust faults; West Pacific
Coordinates: N320000 N330000 E1350000 E1340000
Record ID: 2002012613
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States