1
Q
Any surface or narrow zone with
measurable slip (shear displacement).
A
Faults
2
Q
Consist of fault rock material and subsidiary brittle structures and therefore have a definable thickness.
A
Faults
3
Q
A discontinuity in the velocity or
displacement field associated with
deformation.
A
Faults
4
Q
Loss of cohesion and slip occurs on
several faults within a band of definable width.
A
Fault Zone
5
Q
In a fault zone, the width of the zone depends on the _________ _____ _____________ – it ranges from cm to km when studying large-scale faults.
A
Scale of Observation
6
Q
Regions of localized but continuous ductile displacement. Rocks does not lose mesoscopic cohesion, so that strain is distributed across a band of definable width.
A
Shear Zone
7
Q
Analogs in a ductile material of faults in a brittle material. Hence, shear zones are thus __________ _____________.
A
Ductile Faults
8
Q
Rocks deform by _______________ (a process involving fracturing, crushing, and frictional sliding of grains or rock fragments) or by crystal plastic deformation mechanisms.
A
Cataclasis
9
Q
From what theory of faulting does the information below fit?
1 of the 3 principal stresses must be perpendicular to the surface.
The other 2 must be parallel.
A
Anderson’s Theory of Faulting
10
Q
Fault Geometry:
fault block beneath the fault
surface.
A
Footwall
11
Q
Fault Geometry:
where a layer or feature in the
footwall is cut by the fault.
A
Footwall cut-off
12
Q
Fault Geometry:
fault block above the fault surface.
A
Hanging Wall
13
Q
Fault Geometry:
where a layer or feature
in the hanging-wall is cutby the fault.
A
Hanging wall cut-off
14
Q
Fault Geometry:
relative offset of points once
adjacent on either side of a fault.
A
Displacement
15
Q
Fault Geometry:
rocks that have been translated
great distances away from their
original site.
A
Allochthonous
16
Q
Fault Geometry:
rocks that have
retained their
original location.
A
Autochthonous
17
Q
Fault Geometry:
locally transported
rocks.
A
Parautochthonous
18
Q
Fault Geometry:
is a planar geomorphic feature
formed by offset of the surface.
A
Fault scarp
19
Q
Fault Geometry:
The fault that intersected the ground surface while it was active is an ____________ __________.
A
Emergent Fault
20
Q
Fault Geometry:
__________ __________ are faults that did not break the surface.
A
Blind Fault
21
Q
Fault Geometry:
The largest faults in a faulted area,
called _________ _________, are associated with minor faults.
A
Master Faults
22
Q
Fault Geometry:
dips toward the
master fault.
A
Antithetic fault
23
Q
Fault Geometry:
dips in the same
direction as the master fault.
A
Synthetic fault
23
Q
Fault Geometry:
Faults with a displacement of down-dip
A
Normal
24
Fault Geometry:
Faults with a displacement of up-dip
Reverse
25
Extensional faulting (lengthening) is associated to __________ Faulting.
Normal
26
Contractional (Shortening) faulting is associated to __________ Faulting.
Reverse
27
low-angle (0-45°)
reverse faults.
Thrust faults
28
Type of stress that leads to the genesis of Normal Faults.
Tensional Stress
29
Type of stress that leads to the genesis of Reverse Faults.
Compressional Stress
30
High angle, dip-slip fault on
which the hanging-wall has
moved down relative to the
footwall.
Normal Fault Systems
31
Younger rocks over older ones;
because of the separation of
geological horizons, normal
faults are also termed ___________
faults.
Extension
32
Extensional ramps termed
_____________ cut down section
in the direction of transport.
Detachments
33
Normal Fault Systems forms in?
Rifts, passive Margins, and Mid-Ocean Ridges
34
Comprise relay or parallel arrays; theyncan be listric or planar or contain distinct fault bends.
Normal Fault Systems
35
In Normal Fault Systems, Movement generally results in rotation of hanging-wall blocks, causing tilting of overlying fault blocks and/or formation of rollover ____________ and ___________.
anticlines and synclines
36
dip angle is less than 45°.
Low-angle fault
37
dip more than 45°.
Steep faults (High-angle fault)
38
decrease in dip with depth.
Listric fault
39
are concave upward, dip-slip displacements that occur in many tectonic and sedimentary environments.
Listric faults
40
Preferential stratigraphic thickening
in space created by successive, downward displacement of fault blocks
Shelf margin, delta front
41
Shelf and delta margin
formed by ____________.
Slumping
42
normal faults dipping away
from each other create an
upthrown block.
horst
43
normal faults dipping
toward each other create a
downthrown block.
graben
44
bounded by a normal
fault on only one side.
Half-graben
45
A dip-slip fault on which the
hanging-wall has moved up and
over the footwall.
Reverse Fault Systems
46
Old rocks lay over younger ones;
produce a repetition or overlap of
a geological horizon and are
accordingly termed _____________ ______________.
contractional/compression fault.
47
A _________fault is a low-angle
reverse fault along which the
hanging wall forms thrustsheets (nappes) of allochthonous rocks
emplaced over the autochthonous or parautochthonous footwall.
Thrust
48
T or F
Most common, thrust faults
ramp up section towards the
surface in the direction of
tectonic transport.
T
49
Thrust fault often run parallel to
bedding (flat) then cut up
through the layers (ramp) before
finding another weak layer to
follow.
Flat-Ramp Structure
50
T or F
Flat-ramp geometries generally
develop best in sequences of
well-stratified sedimentary rock.
T
51
Thrust slices (horses) above a décollement along incompetent (weak) layers.
Bounded by a flat-lying roof thrust and a floor thrust (also sole thrust) enclosinga stacked-up pile of horses.
Covered by a major upper thrust sheet.
Duplex Structure
52
Fan-like splay of thrust panels and
thrust faults generated from a singlevdécollement. Unlike duplexes, there is no roof thrust.
Imbricate zone/fan or schuppen
structure
53
_____________ _____________ often result in the stacking up of a series of thrust
sheets separated by subparallel
thrust faults.
Thrust Sequences
54
Stress Meausurements:
Forces related to plate tectonics and stress regimes expected from these forces.
World Stress Map
55
If erosion produces a hole in a thrust sheet so that at the ground surface we see an exposure of the footwall completely surrounded by hangingwall rocks, then the exposure is called a ___________ or ____________.
window or fenster.
56
Alternatively, if erosion removes
most of a thrust sheet so that you
can map a remnant of the
thrust sheet that is completely
surrounded by footwall strata, then
the "island" of hanging-wall rock is
called a ______________.
klippe
57
Two types of displacement in a strike-slip/horizontal slip fault.
Right-Lateral and Left-Lateral
58
Usually have very steep or
vertical dips and the relative
movement between the
adjacent blocks is horizontal,
parallel to the strike of the
fault plane.
Strike-Slip Fault Systems
59
T or F
Major strike-slip faults can be
several hundred kilometers
long and are not simple
planar movement planes.
T
60
Large strike-slip faults are
referred to as?
transcurrent faults and wrench faults
61
Transfer displacement/slip
between two similarly oriented
fault segments (e.g. two normal
faults).
Transfer fault
62
Usually confined to hanging
walls of detached systems and
terminate where they connect
the linked faults.
Transfer fault
63
strike slip fault at plate boundaries.
Transform fault
64
Three types of Transform Faults.
Ridge-ridge, Trench-trench, and Ridge-Trench
65
repeatedly offset the ocean ridges to accommodate differences in the spreading rates of either side of a ridge and/or between neighboring segments (e.g., Romanche transform zones separating the African and South American plates).
Ridge-Ridge
66
link two segments of a destructive plate boundary (e.g.. Alpine Fault, New Zealand.
Trench-Trench
67
connects spreading to convergent plate boundaries. A subtype would link a ridge to a mountain belt (e.g., Middle-East Fault, which links the Red Sea spreading center to the N-Syria-E-Turkey collision mountains.
Ridge-Trench
68
A mechanism that synchronouslyforms a subduction zone and a strike-slip fault. The normalstress is accommodated by the subduction/trench system.The shear stress is accommodated by a strike-slip fault.
Shear partitioning
69
The ___________ ___________ is a product of the obliqueconvergence between the Philippine Sea Plate and the Philippine Mobile Belt.
Philippine Fault
70
___________-___________ transform faults are
the most common.
Ridge-ridge
71
They are fracture zones striking at
nearly right angles to the mid-oceanic
ridges and seemingly offsetting the ridges.
Ridge-Ridge transform faults
72
show both dip-slip and strike-slip motion.
Oblique-slip faults
73
the amount of slip
changes along strike so that the
hanging-wall block rotates around an
axis that is perpendicular to the fault
surface.
Scissors fault
74
displacement of one fault
block relative to the other.
Net slip
75
To describe net-slip, ________ and _________ _______ __________ must bedetermined.
rake and sense of slip
76
angle between the strike
of the slip surface and the slip vector.
Rake/Pitch
77
relative displacement of
one wall of the fault with respect to the
other wall; whether one wall went up
or down, and/or to the left or right of
the other wall.
Sense of slip
78
T or F
Faults accumulate displacement as
they grow in length and height.
T
79
The apparent displacement that is
observed on a section or plane is
called the __________ ___________.
Apparent Separation
80
separation of
layers observed on a horizontal
exposure or map.
Horizontal separation
81
separation of layers in
a vertical section.
Dip separation
82
Dip separation can be decomposed into?
Heave and Throw
83
Dip separation
(vertical component)
Throw
83
Dip separation
(horizontal component)
Heave
84
Missing stratigraphic section or repeated section in wells drilled through a fault.
Stratigraphic separation
85
For vertical wells at the fault cut,
___________ ____________ always indicate normal faults.
Missing section
86
For vertical wells at the fault cut,
___________ ____________ occurs where the normal fault is steeper than the intersecting wellbore.
Repeated section
87
____________ _____________ (or slip
surface) - most intensely
deformed part of a fault,
composed of crushed
and shattered rock.
Fault core
88
surrounding area of less
intense deformation,
characterized by
fractures, subsidiary
faults, and veins that
decrease in density with
distance from the fault
core.
Damage zone
89
along a fault zone. It
tends to have a mах.
displacement in the
central part, gradually
decreasing toward the
tips.
Displacement distribution
90
Non-foliated incohesive fault rocks.
Fault Gouge, Fault Breccia, and Indurated Gouge/Breccia
91
Non-foliated cohesive fault rocks.
Cataclasite and Pseudotachylyte
92
Foliated cohesive fault rocks.
Mylonites
93
composed of angular fragments of rock> 1 mm to several m in diameter.
Fault breccia
94
composed of fine-grained rock flour (< 1mm) produced by
continued displacement across the fault zone.
Fault gouge
95
The network of fractures between fragments in breccia and gouge allows groundwater to pass through the fault zone, allowing precipitation of minerals (i.e., quartz, calcite).
As a result, fragments are cemented together by minerals precipitated from fluids (i.e., groundwater) producing _____________ _____________.
indurated gouge/breccia.
96
T or F
Faults cannot act as conduits or seals/bariers to fluid flow.
F, it can.
97
As __________ they provide a focus for groundwater flow, geothermal
activity, mineralization, and hydrocarbon migration.
conduits
98
As __________ they impede both the vertical and lateral components of fluid flow and contribute to trapping of buoyant fluids
like oil and gas.
seals/barriers
99
The ______________ will depend on the degree of fracturing and the interconnectedness of fractures.
permeability
100
the fragments interlock, allowing the fragmented rock to
remain coherent even without cementation.
Cataclasite
101
Cataclasite
10–50% of the rock is matrix
Protocataclasite
102
Cataclasite
50-90% of the rock is matrix
Cataclasite (sensu stricto)
103
Cataclasite
90-100% of the rock is matrix
Ultracataclasite
104
glass or microcrystalline material that forms whennfrictional heating melts rock during slip on a fault. Pseudotachylyte commonly flows into cracks between breccia fragments or into cracks penetrating the walls of the fault. It may be several m thick (e.g., impact sites), but generally it is mm to cm in thickness.
Pseudotachylyte
105
ell foliated and commonly also lineated
and show abundant evidence of plastic
deformation mechanisms rather than
frictional sliding and grain crushing. They
form at greater depths and temperatures
than cataclasites and other fault rocks
(e.g., above 300C for quartz-rich rocks).
Subdivided based on the amount of
large, original grains and recrystallized
matrix.
Mylonites
106
a smoothly polished surface caused by frictional movement between rocks along a fault.
Slickensides
107
This surface is typically
striated with linear
features, called
__________, in the
direction of
movement.
slickenlines
108
Surface irregularities may
show a striated or stylolitic
surface facing movement
(compression) direction of
the missing block and
unstriated slopes towards
the movement (extension)
direction.
Defines dissolution surfaces
facing the displacement
direction with microstylolitic
peaks pointing in the
upstream direction at a low
angle to the fault surface.
Slickolite
109
Five types of Fault Terminations
Wing cracks, Horsetail splay, Synthetic Splay, En enhelon fractures, and Antithetic splay
110
Fault terminations
occur where there is a rapid
decrease in the slip at the fault tip.
Wing cracks
111
Fault terminations
develop where slip dies out
more gradually towards the fault tip than for
wing cracks.
Horsetail splay
112
Fault terminations
are geometrically and
mechanically similar to wing cracks but are
finer and more closely spaced with relatively
low angles to the master fault. They have the
same sense of slip as the main fault and may
link with a neighboring fault segment.
Synthetic splay
113
Fault terminations
formed due to the
localized extension that occurs inside the shear
zone.
En enhelon fractures
114
Fault terminations
have a sense of slip opposite
to that of the main fault and tend to develop
at high angles to the master fault. They are
isolated fractures separated from the master
fault and often increase their length and
spacing away from the fault tip.
Antithetic splay
115
Subsidiary shear fractures that propagate a short distance out of the
main fault but are coeval with it.
The geometrical arrangement of is indicative of the sense of movement within the fault zone and is therefore widely used for the interpretation of its kinematic evolution.
Riedel shears
116
normally the first
subsidiary fractures to occur and
generally build the most
prominent set.
They develop at an acute angle,
typically 10-20° clockwise to a
dextral main fault.
Synthetic to the main fault.
R shears
117
may develop with or
after R shears. A second set of
faults at about 75o to the PDZ are
conjugate to the Riedel shears
and antithetic to the PDZ.
Veins Conjugate shear fractures
They are oriented at high angle,
approx. 75° clockwise to a dextral
main fault.
Antithetic to the main fault.
R' shears
118
As shear continues, a third set
of fractures ____ ____________
develops.
Link together the previously
formed Riedel shears, and,
eventually, a throughgoing
fault zone consisting of linked
R-, R'-, and P-shears develops.
P Shears
119
Faults and folds commonly occur in the same
outcrop.
The transition between brittle and ductile
deformation can depend on strain rate.
Recall: If ductile strain (e.g., folding) in a rock
body develops fast enough to accommоdate
regional deformation, then differential stress
does not get very high in the rock and faulting
need nof occur.
Fault-Related Folding
Structural Geology
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