Announcements Mihai's lectures are available on web Field trip during lab this week Posta-Quemada fold exercise- due Wed in lecture Nov. 13: Draft of fault paper due in lecture!

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AnnouncementsMihai's lectures are available on
webField trip during lab this
weekPosta-Quemada fold exercise- due Wed in
lectureNov. 13 Draft of fault paper due in
lecture!
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Strike-slip fault systems(DR 357-371)
1. Tectonic settings and significance 2.
Geometries 3. Active strike-slip faults-
EQs!4. mineralization petroleum
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At the scale of plate tectonics, transform
(strike-slip) plate boundaries are subordinate to
convergent and divergent plate margins- but they
play a critical role
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oceanic (ridge-ridge) transform faults, revisited
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Continental strike-slip faults- the San Andreas
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The Alpine fault in New Zealand transfers slip
between two subduction zones (trench-trench
transform)
What is the sense of slip?
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Major active continental strike-slip faults in
Asia
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tectonic extrusion or escape hypothesis
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Strike-slip faults can transfer slip between
different thrust or extensional systems
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Strain can be partitioned into different styles
of fault systems- analyze with vector diagrams
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Strain partitioning in oblique convergent margin
settings
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Fault traces are rarely straight- they can curve,
branch, or be arranged en echelon. This leads to
a wide variety of strike-slip related deformation
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Transtension in releasing bends may lead to
development of sag ponds and pull-apart basins
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Restraining bends and transpressional
deformation- folds and thrusts
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The San Andreas bend near Los Angeles thrusting
related to strike-slip faulting
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Many strike-slip fault systems are characterized
by faults that converge downward and form flower
structures
compressional setting "positive" or "palm tree"
flower structure
extensional setting "negative" or "tulip"
flower structure
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Some flower structures look like duplexes turned
on their side- strike-slip duplexes
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Riedel shears, revisited- especially common in
strike-slip fault systems
R synthetic Riedel shearR' antithetic Riedel
shearP synthetic shear, subordinate to R and R'
or absent
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Altyn Tagh fault, China
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summary of strike-slip-related deformation
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What is important about strike-slip faults and
why do we care? 1. Many active strike-slip
faults are associated with high slip rates, major
earthquakes, and lithospheric plate boundaries
Big faults yield big quakes lots of people
trouble! e.g., San Andreas fault, Anatolian
fault in Turkey, strike-slip faults in Asia
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Significance of strike-slip fault systems for oil
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Many Archean and Phanerozoic mineral deposits
(especially gold) are associated with zones of
strike-slip deformation
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NEXT LECTURE Cleavages and passive folding (DR
pp. 424-456)
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• Important terminology/concepts
• ridge-ridge and trench-trench transform faults
• concept of continental extrusion or escape
• strike-slip faults as transfer faults
• strain partitioning
• oblique convergence
• releasing vs. restraining bend
• transpression vs. transtension
• sag ponds and pull-apart basins
• flower structures
• strike-slip duplexes
• right-stepping vs. left-stepping fault arrays
• folds in strike-slip zones
• Riedel shears