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GEOL 360 Fault related folds: Geometry & kinematics.

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Presentation on theme: "GEOL 360 Fault related folds: Geometry & kinematics."— Presentation transcript:

1 GEOL 360 Fault related folds: Geometry & kinematics

2 Outline Fault Related Folds (Fault Propagation, Fault Bend, Buckle) Pre-Tectonic, Syn-Tectonic, and Post-Tectonic Deposition Exercise

3 Fault Bend Folds Fault Propagation Folds Includes Trishear Folds Decollement Buckle Folds

4 Growth Strata on Buckle Folds: Both limbs exhibit progressive limb rotation Common above salt layers

5 Chuhuangkeng Anticline Taiwan Decollement Bucking Examples Bavarian Alps (Jura)

6 Outcrop scale buckle fold, Spanish Pyrennees

7 Halfway River, Northern Canadian Rocky Mountains

8  Flat-ramp-flat geometry for fault surface  Fault surface exists across entire cross-section  Fold develops above ramp where limb angles related to fault dip Fault Bend Folds

9 Shear in hangingwall can affect limb width and fold geometry

10 Fault-Propagation Folds Fault tip propagates thru cross-section Fold develops above ramp with uniform forelimb angles Original FPP has forelimb with same dip, trishear dips flatten upwards (trishear = reality)

11 Downtown Osaka Now lets move to Japan… Uemachi Upland/Fold Kuwana Anticline

12 Osaka Bay Osaka Bay Flexure

13 Dip profile of forelimb of Osaka Bay TrishearFPF/blind thrust Most of reflectors are growth strata km of sediment fill in the last 1800 ka Note homogeneous shear in forelimb

14 Dip profile of forelimb of Osaka Bay FPF/blind thrust Most of reflectors are growth strata km of sediment fill in the last 1800 ka Note homogeneous shear in forelimb

15 Best fit trishear solution yields: steep (74 deg) thrust, 12km upward propagation (Fault tip from 15->3km) 10 deg apical angle Dip profile of forelimb of Osaka Bay FPF/blind thrust

16 Fault Propagation Fold (Trishear) movie

17 Fault Propagation Fold (Trishear) movies (Stuart Hardy)

18 Fault Bend folding: Pregrowth strata Bends in fault produce bending in hangingwall, marked by active axial surfaces

19 Fault Bend folding: Pregrowth strata Fault Bend folding: Limbs widen self similarly Growth triangle records progressively more slip with time Inactive axial surfaces once at axial surfaces, now translated above thrust

20 Fault Bend folding: Limbs widen self similarly Growth triangle records progressively less slip

21 Post tectonic Post tectonic deposition caps growth triangles

22 Exercise post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the age of initiation of faulting?

23 Exercise post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the age of initiation of faulting? 13 Ma

24 Exercise post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the age of termination of faulting?

25 Exercise post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the age of termination of faulting? 6 Ma

26 Exercise post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the slip rate on the thrust? 4km 5km 6km

27 post- tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2Ma2Ma 18 Ma 20 MaWest East Depth (m) 400 What is the slip rate on the thrust? 2km 4km 6km

28 post-tectonic 16 Ma 14 Ma 10 Ma 12 Ma 8 Ma 6 Ma 4 Ma 2 Ma 18 Ma 20 MaWest East Depth (m) 400 What is the slip rate on the thrust? 1 mm/yr 2km 4km 6km


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