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; Sanchez-Gomez, Mario; Smith, David C.; Spivack, Arthur J.; Steurer, Joan; Tobin, Harold J.; Ujiie, Kohtaro; Underwood, Michael B.; Wilson, Moyra (2002): Porosity loss within the underthrust sediments of the Nankai accretionary complex; implications for overpressures. Geological Society of America (GSA), Boulder, CO, United States, Geology (Boulder), 30 (1), 19-22, georefid:2002-012613

Abstract:
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, lambda (super *) , of approximately 0.42, where lambda (super *) = [(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 lambda (super *) = approximately 0.47 was estimated, reflecting the additional loading due to recent thickening by the frontal thrust.
Coverage:
West: 134.0000 East: 135.0000 North: 33.0000 South: 32.0000
Relations:
Expedition: 131
Site: 131-808
Expedition: 132
Expedition: 190
Site: 190-1173
Site: 190-1174
Expedition: 196
Site: 196-1173
Site: 196-808
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2002-012613 (c.f. for more detailed metadata)
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