recognizing faults practice with thrust faults and normal faults practice with thrust faults and...
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Recognizing faultsRecognizing faults
Practice with thrust faults and
normal faults
Practice with thrust faults and
normal faults
Why study faults?
Classification of faults:
- each type of fault forms under different geologic conditions
- so, if we can characterize the nature of the fault, we can conclude something about the geologic history...
Some are harder to see ……an extensional fault
• The fault is here<===(normal fault)
Death Valley (photo by M. Miller)
<========
The level land has dropped DOWN
Orientation of fault surfaces:
Strike and Dip
strik
e
dip
Note: for mechanical reasons fault planes are seldom planar over long distances…thus, we must take MANY strike and dip measurements along a fault.
The Nature of Fault Shapes
• Faults are not infinite
• Faults can be irregularly shaped
Wytch Farm Oil Field, southern England (taken from Kttenhorn & Pollard, AAPG Bull, 2001)
CompressionA thrust fault
showing how layers have moved. (black is a layer of coal)
Hanging wall
Foot wall
Compression: Distortion along a fault
• Movement drags on the rock next to this thrust fault.
• The layers
became bent
when the walls
moved.
Fault
Hanging wall
Foot wall
Extension
• An area of extension is called Basin and Range topography.
(the flat areas are basins, the mountains are ranges)
Extension• Can you see a normal fault in this picture?
Hanging Wall
Foot Wall
The black shale layer has dropped down compared to the other side.
http://raider.muc.edu/~mcnaugma/structur.htm
#1 Is this a normal
or thrust fault?
http://virtual.yosemite.cc.ca.us/ghayes/Death_Valley_Friday.htm
Hanging wall
Foot wall
#2 Is this a normal or thrust fault?
http://raider.muc.edu/~mcnaugma/structur.htm
Hanging wall
Foot wall
(Same layer)
#3 Is this a normal or thrust fault?
Hanging wall
Foot wall
(older rock)
(younger rock)
http://raider.muc.edu/~mcnaugma/structur.htm
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