Faults are typically not well exposed Faults have a strike and a dip Faults can be curved There are specific symbols in map view and cross section for normal reverse amp strikeslip ID: 1022587
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1. FaultsCan be very common in a particular areaFaults are typically not well exposedFaults have a strike and a dip. Faults can be curvedThere are specific symbols in map view and cross section for normal, reverse, & strike-slipSince a fault is a surface, you can make a structure contour map of a fault
2. Faults vs. FracturesFractures tend to be more planar, but both are planar to curvi-planarFaults show offset, often have some width, and are typically associated with fracturesFractures show no offset
3. Normal fault Reverse fault Strike-slip fault(dextral)
4. Normal faultsHanging wall moves down with respect to footwallTypically dip about 60 degreesGrabens are the blocks between two normal faults that dip toward each other (at Earth’s surface); Horsts are the blocks between two normal faults that dip away from each other. Half-grabens are like a series of domino blocks, with all normal faults dipping the same wayNormal fault result in horizontal elongation
5. Ancient faults
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7. Normal faults in the field
8. BeforeAfterNote that the lower picture is longer sideways because faulting elongated in the horizontal.
9. Active faults
10. Paradox basin, UTHorst & Grabens
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12. Half-grabens
13. Horst & graben or half-grabens?
14. Fault ScarpsBeforeAfter
15. Reverse FaultsHanging wall moves upward with respect to footwall. Called a “thrust” fault if it occurs at low dip anglesAssociated with foldsTypically dip about 30 degrees, unless forming along a sedimentary layerReverse faults result in horizontal shortening
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18. Relation of reverse faults to folds
19. BeforefterNote tht the lower figure hs shortened horiontlly because of the reverse fult
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21. Cn you determine which is the footwll & which is the hnging wll?
22. Strike-slip faultsTypically dip steeply or are verticalCan curve dramatically (large-scale restraining and releasing bends)Can have a lot of offset (1000s of km)Structure contour maps of stratigraphy affected by a strike-slip faults typically don’t do much
23. It is difficult to notice strike-slip faults in the ancient systems, unless there is large offset. Typically the geology on opposite sides of the fault don’t line up.
24. ctive fults
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26. Stream offsetWallace Creek; San Andreas fault system
27. BeforeAfter