Recognizing faults Practice with thrust faults and normal faults Practice with thrust faults and...
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Transcript of Recognizing faults Practice with thrust faults and normal faults Practice with thrust faults and...
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