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Slide 1

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Fault - Definition
Faults are planar surfaces
within rocks along which
movement has taken place
Faults are created by Tensional,
Compressional or Shear Forces…read more

Slide 2

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Types of Faults
Dip-Slip Faults where movement occurs vertically
Normal Fault ­ caused by Tensional or Pulling
apart forces resulting in crustal extension
Reverse Fault ­ caused by Compressional or Pushing
together forces resulting in crustal shortening
Thrust Fault ­ a reverse fault that dips at <45°
Strike-Slip Faults(Tear Faults) where movement occurs horizontally
Right Lateral or Dextral Tear Fault
where relative movement is to the right due to shear forces
Left Lateral or Sinistral Tear Fault
where relative movement is to the left due to shear forces…read more

Slide 3

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Hanging Wall and Footwall
Fault Plane
Hanging Wall refers to the
rocks on top of the fault plane
Footwall refers to the rocks
underneath the fault plane
If it was possible to pull the blocks apart and walk
into the gap between them, then the side with rocks
overhanging your head would be the Hanging Wall.
The side that you could walk up, would be the Footwall…read more

Slide 4

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Upthrown and Downthrown Blocks
Upthrown and Downthrown are RELATIVE terms
Immediately after faulting the landscape
on the Upthrown Block will be higher
than on the Downthrown Block
Over time the Upthrown Block will
be eroded downwards to match
the level of the Downthrown Block
This means that the rocks exposed at the surface
on the Downthrown Block will be younger than
those on the surface of the Upthrown Block…read more

Slide 5

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Upthrown and Downthrown Blocks
Erosion of the Upthrown Block exposes strata
at the surface which were previously at depth
Rocks above red lines
removed by erosion
Older rocks Younger rocks
on this side on this side…read more

Slide 6

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Marker Beds
These are used to establish the relative
displacement of rocks across a fault
A Marker Bed is one that is instantly recognisable
on both sides of the fault due to its characteristic
colour, thickness, grain size, mineralogy or fossil content
Thin white layer is the
best marker bed here…read more

Slide 7

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