Post on 02-Feb-2016
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GEOL 360 Fault related folds: Geometry & kinematicsGEOL 360 Fault related folds: Geometry & kinematics
OutlineOutline
• Fault Related Folds (Fault Propagation, Fault Bend, Buckle)
• Pre-Tectonic, Syn-Tectonic, and Post-Tectonic Deposition
• Exercise
Fault Bend Folds
Fault Propagation Folds
Includes Trishear Folds
Decollement Buckle Folds
Growth Strata on Buckle
Folds: Both limbs exhibit
progressive limb rotation
Common above salt layers
Chuhuangkeng Anticline Taiwan
Decollement Bucking ExamplesBavarian Alps (Jura)
Outcrop scale buckle fold, Spanish PyrenneesOutcrop scale buckle fold, Spanish Pyrennees
Halfway River, Northern Canadian Rocky Mountains
Flat-ramp-flat geometry for fault surfaceFlat-ramp-flat geometry for fault surface Fault surface exists across entire cross-sectionFault surface exists across entire cross-section Fold develops above ramp where limb angles related to fault dipFold develops above ramp where limb angles related to fault dip
Fault Bend FoldsFault Bend Folds
Shear in hangingwall can affect limb width and fold geometryShear in hangingwall can affect limb width and fold geometry
Fault-Propagation FoldsFault-Propagation Folds
Fault tip propagates thru Fault tip propagates thru cross-sectioncross-section
Fold develops above ramp Fold develops above ramp with uniform forelimb angleswith uniform forelimb angles
Original FPP has forelimb with same dip, trishear dips flatten upwards (trishear = reality)
Downtown OsakaDowntown Osaka Now lets move to Japan…Now lets move to Japan…
Uemachi Upland/FoldUemachi Upland/Fold
Kuwana AnticlineKuwana Anticline
Osaka BayOsaka Bay
Osaka Bay FlexureOsaka Bay Flexure
Dip profile of forelimb of Osaka Bay TrishearFPF/blind thrustDip profile of forelimb of Osaka Bay TrishearFPF/blind thrust
Most of reflectors are growth strataMost of reflectors are growth strata
1.5-2.0 km of sediment fill in the last 1800 ka1.5-2.0 km of sediment fill in the last 1800 ka
Note homogeneous shear in forelimbNote homogeneous shear in forelimb
Dip profile of forelimb of Osaka Bay FPF/blind thrustDip profile of forelimb of Osaka Bay FPF/blind thrust
Most of reflectors are growth strataMost of reflectors are growth strata
1.5-2.0 km of sediment fill in the last 1800 ka1.5-2.0 km of sediment fill in the last 1800 ka
Note homogeneous shear in forelimbNote homogeneous shear in forelimb
Best fit trishear solution yields: steep (74 deg) thrust, 12km Best fit trishear solution yields: steep (74 deg) thrust, 12km upward propagation (Fault tip from 15->3km) 10 deg apical upward propagation (Fault tip from 15->3km) 10 deg apical angleangle
Dip profile of forelimb of Osaka Bay FPF/blind thrustDip profile of forelimb of Osaka Bay FPF/blind thrust
Fault Propagation Fold (Trishear) Fault Propagation Fold (Trishear)
moviemovie
QuickTime™ and aGIF decompressorare needed to see this picture.
Fault Bend folding: Pregrowth strataFault Bend folding: Pregrowth strata
Bends in fault produce bending in hangingwall, Bends in fault produce bending in hangingwall, marked by active axial surfacesmarked by active axial surfaces
Fault Bend folding: Pregrowth strataFault Bend folding: Pregrowth strata
Fault Bend folding: Limbs widen self similarlyFault Bend folding: Limbs widen self similarly
Growth triangle records progressively more slip with timeGrowth triangle records progressively more slip with time
Inactive axial surfaces once at axial surfaces, Inactive axial surfaces once at axial surfaces,
now translated above thrustnow translated above thrust
Fault Bend folding: Limbs widen self similarlyFault Bend folding: Limbs widen self similarly
Growth triangle records progressively less slipGrowth triangle records progressively less slip
Post tectonic
Post tectonic deposition caps growth trianglesPost tectonic deposition caps growth triangles
ExerciseExercise
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East0
100
200Dep
th (
m)
400
What is the age of initiation of faulting?What is the age of initiation of faulting?
ExerciseExercise
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East0
100
200Dep
th (
m)
400
What is the age of initiation of faulting? What is the age of initiation of faulting? 13 Ma13 Ma
ExerciseExercise
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East0
100
200Dep
th (
m)
400
What is the age of termination of faulting? What is the age of termination of faulting?
ExerciseExercise
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East0
100
200Dep
th (
m)
400
What is the age of termination of faulting? What is the age of termination of faulting? 6 Ma6 Ma
ExerciseExercise
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East0
100
200Dep
th (
m)
400
What is the slip rate on the thrust?What is the slip rate on the thrust?
4km4km
5km5km
6km6km
post-
tectonic
16 Ma14 Ma
10 Ma12 Ma
8 Ma6 Ma4 Ma2
M
a
18 Ma
20 Ma
WestWest East0
100
200Dep
th
(m)
400
What is the slip rate on the thrust? What is the slip rate on the thrust?
2km2km
4km4km
6km6km
post-tectonic
16 Ma
14 Ma
10 Ma
12 Ma
8 Ma
6 Ma
4 Ma2 Ma
18 Ma
20 Ma
WestWest East
What is the slip rate on the What is the slip rate on the
thrust? 1 mm/yr thrust? 1 mm/yr
2km2km
4km4km
6km6km