Porosity loss within the underthrust sediments of the Nankai accretionary complex: Implications for overpressures

Elizabeth Screaton, Demian Saffer, Pierre Henry, Sabine Hunze

Research output: Contribution to journalArticle

93 Citations (Scopus)

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 décollement 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.

Original languageEnglish (US)
Pages (from-to)19-22
Number of pages4
JournalGeology
Volume30
Issue number1
DOIs
StatePublished - Jan 1 2002

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overpressure
porosity
hydrostatic pressure
pore pressure
fluid flow
trench
thrust
sediment
turbidite
dewatering
Ocean Drilling Program
trough
subduction
transect
physical property
permeability
fluid
loss

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

Screaton, Elizabeth ; Saffer, Demian ; Henry, Pierre ; Hunze, Sabine. / Porosity loss within the underthrust sediments of the Nankai accretionary complex : Implications for overpressures. In: Geology. 2002 ; Vol. 30, No. 1. pp. 19-22.
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Porosity loss within the underthrust sediments of the Nankai accretionary complex : Implications for overpressures. / Screaton, Elizabeth; Saffer, Demian; Henry, Pierre; Hunze, Sabine.

In: Geology, Vol. 30, No. 1, 01.01.2002, p. 19-22.

Research output: Contribution to journalArticle

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