1. II. Basic Techniques in Structural Geology
Field measurements and mapping
Terminology on faults and folds
Stereographic projections
From maps to cross-sections
Growth Strata
Fault-related folds
Seismic Imaging

2. Two types of fault-related fold (drawn here assuming flexural slip folding)
Fault-bend fold
Fault-propagation fold

3. Fault-Bend Fold Fault Bend Folds (FBF) =ramp anticlines
throughgoing faults - slip is conserved.
Fold amplitude is determined by the thickness above the lower hanging wall flat.
Once the fold has achieved maximum amplitude, it only grows in width.

4. Duplex system

5. Thrust fault hangingwall and footwall ramps and flats…

6. Fault-Propagation Fold Fault Propagation Folds (FPF)
fault slip is not conserved. Fault displacement is taken up by folding
Fault tip is marked by a ductile ‘process zone’.
Ideally, FPF’s evolve into FBF’s

7. Fault-tip Folds Fault-propagation fold (non-parallel fold)
Detachment fold
(folding is always non-parallel)
Fault-propagation Fold
(parallel fold)

8. ‘Drag folds’ Footwall rocks are commonly deformed into synclines
Could also relate to fault propagation

9. Footwall syncline in the Canadian Cordillera

10. Let’s practice…

12. Primary strucure due to cross-bedding stratification
Primary strucure due to cross-bedding stratification. Not related to deformation

14. Describe: from: http://earth.leeds.ac.uk/learnstructure/index.htm

15. Recumbent tight similar syncline and anticline
similar fold
parallel fold
from:
from:
Recumbent tight similar syncline and anticline
Upright open parallel syncline

16. try to sketch: shallowly plunging, upright, tight, similar syncline
Assume fold axis plunges toward N45E

17. Example from the Argentinian Cordillera

18. What is it?

20. Fault related Folds
all from:

21. Fault related Folds Fault-tip Fold Fault-bend Fold

22. A case study of a fold and thrust belt: The North Tian Shan Piemont
(Charreau et al, 2008)

25. Growth strata record of Kink Band migration (Huerguosi Anticline)
(Charreau et al, 2008)
(Suppe et al., 1997; Hubert-Ferrari et al, 2007)

26. Modeling
12 equations ex:
Kinematic model
(Charreau et al, 2008)

27. (Charreau et al, 2008)

28. Modeling dip angles Bedding expected from the pure
Fault-bend fold model
Bedding measured in surface
Bedding expected from the fault-bend fold
model with growth strata
(Charreau et al, 2008)

29. Long Term History of Shortening
(Charreau et al, 2008)

30. Sedimentation History
Accumulation rates– Piggy back
Accumulation rates- magnetostratigraphy
(Charreau et al, 2008)