Dynamic permeability, consolidation and deformation structures in accretionary prism sediments

Author(s): Maltman, Alex J.; Bolton, Alistair J.
Author Affiliation(s): Primary:
University of Wales, Institute of Earth Studies, Aberystyth, United Kingdom
Volume Title: American Association of Petroleum Geologists 1996 annual convention
Source: Annual Meeting Expanded Abstracts - American Association of Petroleum Geologists, Vol.5, p.89; American Association of Petroleum Geologists 1996 annual convention, San Diego, CA, May 19-22, 1996. Publisher: American Association of Petroleum Geologists and Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States. ISSN: 0094-0038 CODEN: APGAB2
Note: In English
Summary: In the actively deforming materials of modern accretionary prisms there is a close interaction between permeability, mechanical state, and deformation structures. Core-scale structures from the Nankai prism, Japan, suggest that they have acted to localise fluid flow; dynamic permeability values (determined in the laboratory during progressive strain) vary with the strain state and, particularly, consolidation ratio. These interactions have been quantified further in experiments on sediments retrieved during recent ODP Leg 156 drilling of the Barbados prism and on laboratory-generated analogues. Dynamic permeability values vary in a complex manner with the amount of strain, and an important control is the degree of over- or under-consolidation. Moreover, because fluid pressure gradients give rise to variations in effective stress conditions across a sediment, the consolidation state differs locally. Material can be dilating in one part and showing an transient increase in permeability, while nearby areas are compacting and curbing flow. Detailed analysis of pore-volume changes during the experiments links intervals of dilation with the permeability/strain variations and accounts for the local but marked variations in the hydrogeology around the prism decollement. The results help explain evidence from the deformation structures in the decollement that indicate both fluid overpressuring and locally enhanced fluid flow, which implies transient pulsing of the pressurised fluids.
Year of Publication: 1996
Research Program: ODP Ocean Drilling Program
Key Words: 16 Structural Geology; Accretionary wedges; Asia; Atlantic Ocean; Barbados Ridge; Consolidation; Cores; Decollement; Deformation; Dilation; Drilling; Experimental studies; Far East; Japan; Leg 156; Mechanical properties; Nankai Trough; North Atlantic; North Pacific; Northwest Pacific; Ocean Drilling Program; Overpressure; Pacific Ocean; Permeability; Pressure; Sediments; Strain; West Pacific
Coordinates: N153128 N153213 W0584251 W0584453
Record ID: 1997017517
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