Structural Geology Lecture

8/14/2019 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

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Structural Geology Lecture