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Carboneras Fault Features (Field Obv (Phyllosilicate rich fault gouge…
Carboneras Fault Features
1. Fault strand linkage
= portions of fault which accommodate displacement
Carboneras = anastomosing & branching
SAF = linked @ depth
2. Bodies in
fault zone
Carboneras: Dolomite blocks
Very rigid ∴ exhibit angular fracture
Form en echelon arrangements
Reflecting different mechanical properties wrt matrix
Strain hardening?
--> distributed def within well-defined layers as
SAF: Parkfield
Small high
velocity bodies
granular, strain weakening fault rocks ?
narrow zone deformation ?
Microearthquakes
localised fault surface patches undergoing stick slip ?
surrounded by stable sliding areas that slowly feed displacements ?
Slickensides
in fault gouge
Slickensides in phyllosilicate fault gouge
Used to determine fault strand orientations
= smoothly polished surface
normally striated in the direction of movement
Cause: frictional mvmt btwn rocks along the two sides of a fault
Field Obv
Phyllosilicate rich fault gouge
Derived from basement
Abundant strands
Slickensides - infer relative fault strand mvmt
Strain hardening
Igneous Rocks
Intruded into fault to SE
Dolomite
blocks
Highly striated & polished localized fault surfaces
Very rigid ∴ exhibit angular fracture
Deformed along sharp pronounced boundaries
Country rock
Bound by layers of phyllosilicate-rich fault gouge
Variably fractured lenses
Lenses incorporated as new fault gouge strands developed?
Wide def zone
strain hardening of fault gouge
eventually becomes easier to deform undeformed country rock
Strain Partitioning
Folding abundant
on flanks of fault
Transpressive deformation
Compressional element=accomodated by folding
Sediments influenced by transpression even after faulting ceased
3. Fault gouge bands
= portion of fault zone accommodating slip
anastomosing slip surface pattern
encompasses fractured lenses of material deforming less actively
4. Localised fault planes
Often those involved in seismic events
Fault gouge itself has little frictional strength thus fails easily
Strike slip may faults appear as
surrounded by damage zones
Anastomosing shear plane arrays
5. Fault gouge structures
R- shears dip steeply SE
P foliation dipping steeply S
slickenlines
= striations on shears
indicate movement direction