Structural Geology Lecture
Transcript of Structural Geology Lecture
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Stress adirected
pressure whichmay lead tostrain (change
inshape/deformation)
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Topo Maps vs Geologic Maps
Geologic maps formations,members, beds, contacts
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Outcrops
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Things we see: Faults
Occur along breaks movement
Faults are from three types of stress:
Tension
Compression
Shear
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From stresses we get:Faulting
Normal Faults
Reverse Faults
Thrust faults
Sense of motion of the top block
relative to the bottom block(REGARDLESS of which one hasactually moved!)
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Normal Fault
From tensional stress
Normal referring to normal responseto g
Hanging wall black moves downrelative to footwall block
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Reverse Faults Hanging wall block moves up in
relation to footwall Can happen at a high angle (reverse
fault) or low angle (thrust fault)
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Strike Slip Faults
Also known as lateral faults
Motion relative to an observerstanding on one side
Right lateral or left lateral strike-slipfault
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- -Left lateral strike slipfault
- -Right lateral strike slipfault
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Transform Faults (Strike-Slip)
Occur on plate boundaries
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Folded Structures Anticline convex fold, oldest rocks in the
middle Syncline concave fold, youngest rocks in
the middle
Both bend around a fold axis within theaxial plane
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F ld h li b h id f
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Folds have limbs one on each side ofaxial plane
If one limb is under the other overturned
fold
Fold axis may not be horizontal plunging fold
Plunge = angle between fold axis andhorizonal
Trend = the plunge bearing (compassdirection)
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A 3 D A n ticlin e D o m e
-The oldest rocks at!center of the dome
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-Oldest rocks are at the center of!the basin
A 3D Syncline Basin
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Mysteries.(akauncomformities!)
Discomformity Unconformitybetween relatively parallel strata
Angular unconformity - .betweennonparallel strata
Noncomformity unconformitybetween sedimentary rock and
non-sedimentary rock
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Unconformities
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How do we map this stuff?
Strike compass bearing of lineformed by the intersection of ahorizontal plane to an incline layer
D ip a n g leb e tw e e n ah o rizo n ta l p la n e
a n d th e tilte d(stra tu m w a te rru n s d o w na lo n g d ip
d ire ctio n
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. !Check out Fig 10 1