|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Department of Geology, Humboldt State University, Arcata, California 95521, USA
2 Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA
Zones of deformation bands occur in unconsolidated late Pleistocene marine terrace sand in the footwall of the active McKinleyville thrust fault in Humboldt County, California. Individual deformation-band shear zones are as much as 8 cm wide and accommodate 
50 cm of reverse-dip separation. Like deformation bands described in Mesozoic sandstone of the Colorado Plateau, these structures formed in fine-grained, well-sorted, porous sand. We assessed the relative importance of compaction, grain breakage, and grain rotation during shear-zone development by measuring grain size, grain shape, grain orientation, porosity, and bulk strain both within and outside deformation-band shear zones. Sand grains within shear zones are smaller, more compacted, and have stronger preferred orientations and more elongate shapes than grains outside of deformation-band shear zones. Bulk strain analyses of sand within shear zones give strain ellipses that are compatible with dextral shear strains of 0.1–0.5 and volume loss of 5%–15%. On the basis of these observations, we conclude that compaction, grain rotation, and extensive cataclasis all contribute to deformation-band shear-zone formation in these unconsolidated sands, despite very low confining pressures. In addition, the position of these deformation-band shear zones adjacent to an active fault with a history of episodic slip during large earthquakes suggests that they may form in conjunction with slip events.
Key Words: cataclasis • deformation band • active fault
This article has been cited by other articles:
|
|
 |
|
  A. Rotevatn, J. Tveranger, J. A. Howell, and H. Fossen Dynamic investigation of the effect of a relay ramp on simulated fluid flow: geocellular modelling of the Delicate Arch Ramp, Utah Petroleum Geoscience, February 1, 2009; 15(1): 45 - 58. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. E. S. Johansen and H. Fossen Internal geometry of fault damage zones in interbedded siliciclastic sediments Geological Society, London, Special Publications, January 1, 2008; 299(1): 35 - 56. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Fossen, R. A. Schultz, Z. K. Shipton, and K. Mair Deformation bands in sandstone: a review Journal of the Geological Society, July 1, 2007; 164(4): 755 - 769. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. M. Cashman, J. N. Baldwin, K. V. Cashman, K. Swanson, and R. Crawford Microstructures developed by coseismic and aseismic faulting in near-surface sediments, San Andreas fault, California Geology, July 1, 2007; 35(7): 611 - 614. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Evans and K. K. Bradbury Fractured dirt: Deformation textures and processes in sediment and other unconsolidated deposits Geology, July 1, 2007; 35(7): 671 - 672. [Full Text] [PDF]
|
|
|
|
 |
|
 S. M. Cashman and K. V. Cashman Cataclastic textures in La Grange fault rocks, Klamath Mountains, California Geological Society of America Special Papers, January 1, 2006; 410(0): 433 - 450. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. DRAGANITS, B. GRASEMANN, and C. HAGER Conjugate, cataclastic deformation bands in the Lower Devonian Muth Formation (Tethyan Zone, NW India): evidence for pre-Himalayan deformation structures Geological Magazine, November 1, 2005; 142(6): 765 - 781. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. N. Bindeman Fragmentation phenomena in populations of magmatic crystals American Mineralogist, November 1, 2005; 90(11-12): 1801 - 1815. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Vigneresse Rheology of a two-phase material with applications to partially molten rocks, plastic deformation and saturated soils Geological Society, London, Special Publications, January 1, 2004; 224(1): 79 - 94. [Abstract] [PDF]
|
|
|
|
|
|
J. E. Wilson, L. B. Goodwin, and C. J. Lewis Deformation bands in nonwelded ignimbrites: Petrophysical controls on fault-zone deformation and evidence of preferential fluid flow Geology, October 1, 2003; 31(10): 837 - 840. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Draganits, B. Grasemann, and H. P. Schmid Fluidization pipes and spring pits in a Gondwanan barrier-island environment: groundwater phenomenon, palaco-seismicity or a combination of both? Geological Society, London, Special Publications, January 1, 2003; 216(1): 109 - 121. [Abstract] [PDF]
|
|
|
|
|
|
I. G. Main, O. Kwon, B. T. Ngwenya, and S. C. Elphick Fault sealing during deformation-band growth in porous sandstone Geology, December 1, 2000; 28(12): 1131 - 1134. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
