Strike-parallel variations in clay minerals and fault vergence in the Cascadia subduction zone

Online Access: Get full text
doi: 10.1130/0091-7613(2002)030<0155:SPVICM>2.0.CO;2
Author(s): Underwood, Michael B.
Author Affiliation(s): Primary:
University of Missouri at Columbia, Department of Geological Sciences, Columbia, MO, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 30(2), p.155-158. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 30 refs.; illus., incl. sketch maps
Summary: Clay minerals probably affect the zonation of mechanical properties within a thick unit of abyssal-plain deposits as they enter the Cascadia subduction zone. Landward-vergent thrust faults develop above a deeper decollement because smectite-rich mudrocks within that corridor release more water during clay dehydration, which in turn elevates pore pressure and reduces basal shear stress relative to wedge strength. Conversely, dilution of smectite by illite and chlorite increases the frictional coefficient, and fluid overpressure should drop where smectite dehydration is volumetrically reduced. Thus, thrust faults within chlorite-rich segments of the margin are seaward vergent.
Year of Publication: 2002
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 18 Geophysics, Solid-Earth; Accretionary wedges; Cascadia Basin; Cascadia subduction zone; Clastic rocks; Clay mineralogy; Clay minerals; DSDP Site 174; Decollement; Deep Sea Drilling Project; Deep-sea environment; Dehydration; Diagenesis; East Pacific; Faults; Leg 146; Leg 168; Leg 18; Marine environment; Marine sediments; Mudstone; North Pacific; Northeast Pacific; ODP Site 892; Ocean Drilling Program; Pacific Ocean; Plate boundaries; Plate tectonics; Pore pressure; Sedimentary rocks; Sediments; Segmentation; Shear stress; Sheet silicates; Silicates; Smectite; Strength; Subduction zones; Thrust faults
Coordinates: N444026 N444032 W1250705 W1250709
N445330 N445330 W1262048 W1262048
Record ID: 2002014646
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States