Structural Geology Test 1

Front 1

Difference between slip and separation 1

Back 1

Pre-Faulting

Front 2

Difference between slip and separation 2

Back 2

Slip - actual relative displacement between two points that occupied the same location before faulting.

Front 3

Difference between slip and separation 3

Back 3

Separation - apparent relative displacement between two points that may have occupied the same location before faulting.

Front 4

Fault Recognition 1

Back 4

Features of faults themselves:

1. Fault rocks, i.e. Fault Breccia ect.

2. Slickensides, slickenlines etc.

Front 5

Fault Recognition 2

Back 5

Effects on stratigraphic units:

1. Break in continuous stratigraphic section; truncation of structures.

2. Don’t confuse faults w/ unconformities--upper units usually parallel to contact.

3.Horses (fault slices) = blocks surrounded on all sides by faults--usually displaced a large distance from original position

4. Repetition of strata.

5. Omission of strata.

6. Drag folds (also reverse drag).

Front 6

Fault Recognition 3

Back 6

Effects on topography or geomorphology:

1. Scarps.

2. Offset ridges, valleys, streams.

3. Springs, sag ponds.

4. Nickpoints in streams.

Front 7

Modes of Fractures according to tip line 1

Back 7

Tip line: line that separates slipped from unslipped rock; (where fault displacement goes to zero) tip line is a closed loop

Front 8

Modes of Fractures according to tip line 2

Back 8

Mode I fracture: Opening mode

1. A tensile stress normal to the plane of the crack.

Front 9

Modes of Fractures according to tip line 3

Back 9

Mode II fracture: Sliding mode

1. A shear stress acting parallel to the plane of the crack and perpendicular to the crack front.

Front 10

Modes of Fractures according to tip line 4

Back 10

Mode III fracture: Tearing mode
1. A shear stress acting parallel to the plane of the crack and parallel to the crack front.

Front 11

Fleuty's Fold Classification 1

Back 11

Front 12

Fleuty's Fold Classification 2

Back 12

A. Upright:

1. Dip of axial surface is upright or plunge of hingeline is horizontal.

Front 13

Fleuty's Fold Classification 3

Back 13

B. Horizontal inclined:

1. Moderately inclined axial surface and horizontal hingeline.

Front 14

Fleuty's Fold Classification 4

Back 14

C. Recumbent:

1. Dip of axial surface recumbent and plunge of hingeline is horizontal, less than 10 degrees.

Front 15

Fleuty's Fold Classification 5

Back 15

D. Plunging inclined:

1. Dip of axial surface at 60 degrees and plunge of hingeline at 30 degrees.

Front 16

Fleuty's Fold Classification 6

Back 16

E. Reclined:

1. Dip of axial surface at 60 degrees and plunge of hingeline at 60 degrees.

Front 17

Fleuty's Fold Classification 7

Back 17

F. Vertical:

1. Dip of axial surface vertical and plunge of hingeline is upright, more than 80 degrees.

Front 18

Fleuty's Fold Classification 8

Back 18

G. Plunging upright:

1. Gently plunging hingeline and upright dip of axial surface.

Front 19

Ramsay's Isogon Classification for Folds 1

Back 19

Front 20

Ramsay's Dip Isogon Classification for Folds 2

Back 20

A. 1a Class Fold:

1. Strongly convergent

Front 21

Ramsay's Dip Isogon Classification for Folds 3

Back 21

B. 1b Class Fold:

1. Parallel

Front 22

Ramsay's Dip Isogon Classification for Folds 4

Back 22

C. 1c Class Fold:

1. Weakly Convergent

Front 23

Ramsay's Dip Isogon Classification for Folds 5

Back 23

D. 2 Similar Class Fold:

1. Similar

Front 24

Ramsay's Dip Isogon Classification for Folds 6

Back 24

E. 3 Class Fold:

1. Divergent

Front 25

Cylindrical folds vs Non-cylindrical folds 1

Back 25

Cylindrical Folds:

1. Straight hinge lines.

2. Contain fold axes.

Front 26

Cylindrical folds vs Non-cylindrical folds

Back 26

Non- Cylindrical Folds:

1. Curved hinge lines.

2. Does not contain fold axes.

Front 27

Symmetric vs asymmetric folds 1

Back 27

Symmetric:

1. Limbs have equal dips.

Front 28

Symmetric vs asymmetric folds 2

Back 28

Asymmetric:

1. Unequal limb dip angles.

Front 29

Fold younging direction 1

Back 29

Why is is important?

1. Younging direction given by primary structures in folds is important because it determines up and down and defines anticline or syncline.

Front 30

Four basic patterns of fold superposition 1

Back 30

Superimposed fold:

1. Generations of folds that happen after the diagenesis of the bed and its first folding by tectonic events.

2. A superposed fold is younger than structure it folds.

Front 31

Four basic patterns of fold superposition 2

Back 31

A. Type 0:

1. Cannot see as inteference type; axial surfaces parallel.

Front 32

Four basic patterns of fold superposition 3

Back 32

B. Type 1:

1. “Dome-and-basin” structure; egg-carton; axial surfaces normal.

Front 33

Four basic patterns of fold superposition 4

Back 33

C. Type 2:

1. Most difficult to visualize; “mushroom”

Front 34

Four basic patterns of fold superposition 5

Back 34

D. Type 3:

1. “Refolded folds” (all types are refolded)

Front 35

Fold classification by orientation of axial plane and fold axis 1

Back 35

A. Axial plane:

1. Folds can be classified based on the dips of limbs and the axial plane.

2. The spectrum of fold orientations generally corresponds to a gradient in strain.

Front 36

Fold classification by orientation of axial plane and fold axis 2

Back 36

B. Fold axis:

1. Folds can be classified based on the orientation of the fold axis.

2. Horizontal/Non-Plunging or

3. Plunging (Shallow, Moderate, Steep, Vertical, North, South, East, West, etc.)

Front 37

Fold profile view 1

Back 37

A folded surface is fully described in a plane perpendicular to the fold axis. The profile of a fold is the section drawn perpendicular to the fold axis and its axial surface; this contrasts with a geological section which is normally drawn in a vertical plane.

Front 38

Fold Types 1

Back 38

A. Anticline: linear, strata normally dip away from axial center, oldest strata in center.

Front 39

Fold Types 2

Back 39

B. Syncline: linear, strata normally dip toward axial center, youngest strata in center.

Front 40

Fold Types 3

Back 40

C. Antiform: linear, strata dip away from axial center, age unknown, or inverted.

Front 41

Fold Types 4

Back 41

D. Synform: linear, strata dip toward axial centre, age unknown, or inverted.

Front 42

Fold Types 5

Back 42

E. Monocline: linear, strata dip in one direction between horizontal layers on each side

Front 43

Fold Types 6

Back 43

F. Chevron: angular fold with straight limbs and small hinges

Front 44

Fold Types 7

Back 44

G. Recumbent: linear, fold axial plane oriented at low angle resulting in overturned strata in one limb of the fold.

Front 45

Fold Types 8

Back 45

H. Slump: typically monoclinal, result of differential compaction or dissolution during sedimentation and lithification.

Front 46

Fold Types 9

Back 46

I. Ptygmatic: Folds are chaotic, random and disconnected. Typical of sedimentary slump folding, migmatites and decollement detachment zones.

Front 47

Fold Types 10

Back 47

J. Parasitic: short wavelength folds formed within a larger wavelength fold structure - normally associated with differences in bed thickness.

Front 48

Fold Types 11

Back 48

K. Disharmonic: Folds in adjacent layers with different wavelengths and shapes.

Front 49

Fold Types 12

Back 49

J. Harmonic: fold which maintains its geometric form, integral wavelength, and symmetry throughout a sequence of layers

Front 50

Parts of a fold 1

Back 50

A. Crest.

B. Hinge

C. Limb

D. Trough

E. Inflection point: where sense of curvature changes.

F. Hinge line: where curvature is the greatest.

Front 51

Parts of a fold 2

Back 51

A. Enveloping surface (antiform / connect crest).

B. Enveloping surface (synform / connect troughs)

C. Synform: Valley

D. Synclinorium: Regional

E. Antiform: Hill

G. Anticlinorium: Regional

H. Enveloping surface: Defines limit of fold.

Front 52

Types of Unconformities 1

Back 52

A. Angular unconformity:

1. Are those where an older package of sediments has been tilted, truncated by erosion, and than a younger package of sediments was deposited on this erosion surface.

Front 53

Types of Unconformities 2

Back 53

B. Disconformity:

1. The surface of a division between parallel rock strata, indicating interruption of sedimentation.

Front 54

Types of Unconformities 3

Back 54

C. Non-conformity:

1. Are unconformities that separate igneous or metamorphic rocks from overlying sedimentary rocks. They usually indicate that a long period of erosion occurred prior to deposition of the sediments.

Front 55

Types of Faults 1

Back 55

A. Dip-slip faults: Net slip vector parallels dip direction (within 10°).

1. Normal Fault

2. Thrust Fault

3. Reverse Faults

Front 56

Types of Faults 2

Back 56

B. Strike-slip faults: Net slip vector parallels strike direction (within 10°).

1. Right-lateral

2. Left-lateral

Front 57

Types of Faults 3

Back 57

C. Oblique slip faults: Net slip vector not parallel to either strike or dip

1. Left-lateral normal.

2. Right-lateral normal.

3. Left-lateral reverse.

4. Right-lateral reverse.

Front 58

Types of Faults 4

Back 58

D. Scissors/Hinge: One block rotates with respect to the other… rotation perpendicular to fault surface.

Front 59

Piercing Points 1

Back 59

Piercing point is defined as a feature that is cut by a fault, then moved apart. Usually a geologic feature, preferably a linear feature.

Front 60

Components of Fault Displacement 1

Back 60

a. Net slip: Or total slip is the direct distance measured between the two originally adjacent points.

b. Dip slip: Measure of distance between the line of strike and the adjacent point.

c. Strike slip: Measure of distance between the point and where dip slip intersects strike.

Front 61

Components of Fault Displacement 2

Back 61

d. Strike separation: Component of separation parallel to strike.

e. Dip separation: Component of separation parallel to dip.

f1. Heave: Horizontal component of separation.

f2. Throw: Vertical component of dip separation.