II. Basic Techniques in Structural Geology Field measurements and mapping Terminology on faults and...
-
Upload
imogen-stafford -
Category
Documents
-
view
226 -
download
1
Transcript of II. Basic Techniques in Structural Geology Field measurements and mapping Terminology on faults and...
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
Two types of fault-related fold(drawn here assuming flexural slip
folding)
Fault-bend fold Fault-propagation 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.
Fault-Bend Fold
Duplex system
Thrust fault hangingwall and footwall ramps and flats…
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
Fault-Propagation Fold
Detachment fold
(folding is always non-parallel)
Fault-tip Folds
Fault-propagation Fold(parallel fold)
Fault-propagation fold(non-parallel fold)
Footwall rocks are commonly deformed into synclines
‘Drag folds’
Could also relate to fault propagation
Footwall syncline in the Canadian Cordillera
Let’s practice…
• Primary strucure due to cross-bedding stratification. Not related to deformation
Describe:
from: http://earth.leeds.ac.uk/learnstructure/index.htmfrom: http://www.stmarys.ca/academic/science/geology/structural/
similar fold
Recumbent tight similar syncline and anticline
parallel fold
Upright open parallel syncline
from: http://earth.leeds.ac.uk/learnstructure/index.htm
from: http://www.stmarys.ca/academic/science/geology/structural/
try to sketch: shallowly plunging, upright, tight, similar synclineAssume fold axis plunges toward N45E
Example from the Argentinian Cordillera
What is it?What is it?
Fault related Folds
all from: http://earth.leeds.ac.uk/learnstructure/index.htm
http://earth.leeds.ac.uk/learnstructure/index.htm
Fault related Folds
http://earth.leeds.ac.uk/learnstructure/index.htm
Fault-bend FoldFault-tip Fold
A B
A case study of a fold and thrust belt: The North Tian Shan Piemont
(Charreau et al, 2008)
(Suppe et al., 1997; Hubert-Ferrari et al, 2007)
A B
Growth strata record of Kink Band migration (Huerguosi Anticline)
(Charreau et al, 2008)
12 equations ex:
Modeling
Kinematic model
(Charreau et al, 2008)
(Charreau et al, 2008)
Bedding expected from the fault-bend foldmodel with growth strata
Modeling dip angles
Bedding measured in surfaceBedding expected from the pure Fault-bend fold model
(Charreau et al, 2008)
Long Term History of Shortening
(Charreau et al, 2008)
Accumulation rates– Piggy back
Accumulation rates- magnetostratigraphy
(Charreau et al, 2008)
Sedimentation History