Outcrop interpretation of seismic‐scale normal faults in southern Oregon: Description of structural styles and evaluation of subsurface interpretation methods

Davies, Roy; Crawford, Michael; Dula, William F.; Cole, Mary J.; Dorn, Geoffrey A.

doi:10.1190/1.1437750

Cited by 26 publications

(4 citation statements)

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“…1 for definition). Careful measurements of the initial topography of the sediment excluded the possibility of this being an experimental artefact; this is also supported by the fact that most relay ramps reported from natural settings tilt towards the basin (Stewart & Hancock, 1991; Peacock & Sanderson, 1994; Davies et al. , 1997), and only a few tilt towards the land (Larsen, 1988; Peacock et al.…”

Section: Experimental Relay Rampsmentioning

confidence: 90%

Relay ramps as pathways for turbidity currents: a study combining analogue sandbox experiments and numerical flow simulations

et al. 2009

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Unlike for subaerial settings, the impact of subaqueous relay ramps on sediment dispersal is still poorly understood. A combination of analogue laboratory experiments in a sandbox with numerical flow calculations is used to simulate relay ramp topographies on rifting continental margins and to analyse the resulting turbidity current pathways and their deposits. Various scenarios are investigated, including inflow perpendicular and oblique to the relay ramp axis as well as flow constrained by an incised channel on the ramp and by a landward‐directed tilt of the ramp. Without channelling, most sedimentation takes place on the basin floor because the bulk of the flow follows the steepest gradient down the fault and into the rift basin. With a channel along the relay ramp, significant flow occurs initially down the ramp axis, but channel spillover and basinward ramp tilting combine to redirect much of the sediment down the fault slope into the basin. When the relay ramp has a landward‐oriented tilt, most of the current flows down the ramp and deposits its sediment load there and at the foot of the ramp. However, also here a considerable amount of the flow is shed over the hanging wall fault and into the basin, forming a secondary depocentre, while ponding redistributes thin deposits over a wider area of the basin. The quantitative dependence of these results on the specific ramp geometries remains to be investigated further but may bear great importance for refined sedimentary models in subaqueous rifted settings as well as for hydrocarbon exploration therein.

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Section: Experimental Relay Rampsmentioning

confidence: 90%

Relay ramps as pathways for turbidity currents: a study combining analogue sandbox experiments and numerical flow simulations

et al. 2009

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“…Such asymmetric grabens (Gibbs, 1984;Rosendahl, 1987;Groshong, 1989;Jackson and White, 1989) can display a rich assemblage of topographic features (Davison, 1994) such as footwall uplift (Weissel and Karner, 1989), hangingwall subsidence (Gudmundsson and Ba¨ckstro¨m, 1991), and rollover anticlines (Moore and Schultz, 1999). These topographic elements increase in amplitude from zero at the graben terminations to maximum values near the middle regions of the fault, tracking the shape of the displacement distribution (Dawers et al, 1993;Dawers and Anders, 1995;Davies et al, 1997) and location of maximum offset, D max (Barnett et al, 1987;Pollard and Segall, 1987;Walsh and Watterson, 1987;Bu¨rgmann et al, 1994;Soliva and Benedicto, 2004).…”

Section: The New Hourglass Model For Grabens and Implications For Plamentioning

confidence: 99%

The Canyonlands model for planetary grabens: revised physical basis and implications

Schultz

Moore²,

Grosfils

et al. 2007

The Geology of Mars

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“…For an observer on the relay ramp facing in the dip direction of the segments, the fault in front of the observer is the front segment and the fault behind the observer is the rear segment (Figures 1 and 2). If two echelon faults are not connected across the ramp by a continuous fault surface or a zone comparable to the segments themselves, the pair is soft-linked, leaving an active ramp [Davies et al, 1997]. Active ramps may allow fluid communication from the footwall to the hangingwall of the composite structure, for example, for the migration of groundwater or hydrocarbons between two otherwise sealing fault segments.…”

Section: Geometry Of Overlapping Normal Faults In Map Viewmentioning

confidence: 99%

Fault linkage: Three‐dimensional mechanical interaction between echelon normal faults

Crider¹,

Pollard²

1998

J. Geophys. Res.

285

158

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Abstract. Field observations of two overlapping normal faults and associated deformation document features common to many normal-fault relay zones: a topographic ramp between the fault segments, tapering slip on the faults as they enter the overlap zone, and associated fracturing, especially at the top of the ramp. These observations motivate numerical modeling of the development of a relay zone. A three-dimensional boundary element method numerical model, using simple fault-plane geometries, material properties, and boundary conditions, reproduces the principal characteristics of the observed fault scarps. The model, with overlapping, semicircular fault segments under orthogonal extension, produces a region of high Coulomb shear stress in the relay zone that would favor fault linkage at the center to upper relay ramp. If the fault height is increased, the magnitude of the stresses in the relay zone increases, but the position of the anticipated linkage does not change. The amount of fault overlap changes the magnitude of the Coulomb stress in the relay zone: the greatest potential for fault linkage occurs with the closest underlapping fault tips. Ultimately, the mechanical interaction between segments of a developing normal-fault system promote the development of connected, zigzagging fault scarps.

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Outcrop interpretation of seismic‐scale normal faults in southern Oregon: Description of structural styles and evaluation of subsurface interpretation methods

Cited by 26 publications

References 0 publications

Relay ramps as pathways for turbidity currents: a study combining analogue sandbox experiments and numerical flow simulations

Relay ramps as pathways for turbidity currents: a study combining analogue sandbox experiments and numerical flow simulations

The Canyonlands model for planetary grabens: revised physical basis and implications

Fault linkage: Three‐dimensional mechanical interaction between echelon normal faults

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