Lecture 1: Folds (I)

Question 1

-Linear features are measure by

Answer 1

trend and plunge

Question 2

Geological surfaces are measured by-

Answer 2

1. Strike,
2. dip and
3. dip direction

Question 3

Fold angularity MUST be made when looking through the

Answer 3

Profile Plane.

Question 4

MUST look _ _ _ in order to identify if its an _ or _ fold

Answer 4

MUST look down the plunge in order to identify if its an S or Z fold

Question 5

One common occurrence of S and Z folds, is when folds occur at _ scales in _ layer

Answer 5

One common occurrence of S and Z folds is when folds occur at different scales in the same layer

Question 6

Small folds developed on the limbs of larger folds, with the same orientation, are called _ _

Answer 6

parasitic folds

Question 7

Typically, parasitic folds on one limb have _ asymmetry whereas those on the other limb have _ asymmetry

Answer 7

Typically, parasitic folds on one limb have S asymmetry whereas those on the other limb have Z asymmetry

Question 8

There is often a region on the _ where parasitic folds have no _ _ ; they are described as _ (or _ ) folds.

Answer 8

There is often a region on the hinge where parasitic folds have no clear asymmetry; they are described as M (or W) folds.

Question 9

Sometimes mapping the asymmetry of outcrop-scale parasitic folds is a good way to locate the _ of less obvious map-scale major folds.

Answer 9

Sometimes mapping the asymmetry of outcrop-scale parasitic folds is a good way to locate the hinges of less obvious map-scale major folds.

Question 10

The smaller hinges on the parasitic fold are _ to that of the _ fold. What does this tell us? _ _ _ _ _ _ _

Answer 10

The smaller hinges on the parasitic fold are parallel to that of the larger fold. What does this tell us?They must’ve formed at the same time.

Question 11

folds where each layer is folded in step with the adjacent layers. These are called _ folds

Answer 11

folds where each layer is folded in step with the adjacent layers. These are called harmonic folds

Question 12

Sometimes we find layered rocks in which the folds are not so aligned. These are _ folds.

Answer 12

Sometimes we find layered rocks in which the folds are not so aligned. These are disharmonic folds.

Question 13

There is a relationship between the thickness of the layer and the wavelength of fold produced-

Answer 13

The thinner the layer the thinner the fold length. The thicker the layer the larger the fold length

Question 14

_ form when layered materials are deformed

Answer 14

Folds form when layered materials are deformed

Question 15

The orientation of folds must be described by: _ _and _ of the _.
and the _ / _and _ _ of the _ _

Answer 15

The orientation of folds must be described by: The plunge and trend of the hinge and the strike/dip+ dip direction of the hinge surface

Question 16

Kink Bands have _ hinges and _ limbs: they form in _ rocks. Intersecting kink bands from _ _

Answer 16

Kink Bands have angular hinges and straight limbs: they form in anisotropic rocks. Intersecting kink bands from box folds

Question 17

Asymmetric folds should be described as S or Z looking _ _

Answer 17

Asymmetric folds should be described as S or Z looking down plunge

Question 18

Parasitic folds are _ or _ order folds (smaller _ and _) that occur on:
The _ of _ or _ order folds. They are commonly _.

Answer 18

Parasitic folds are minor or second order folds (smaller wavelength and amplitude) that occur on:
the limbs of larger or first order folds. They are commonly asymmetric.

Question 19

Fold wavelength and amplitude should be estimated. Fold wavelength depends on layer _; amplitude is a measure of _.

Answer 19

Fold wavelength and amplitude should be estimated. Fold wavelength depends on layer thickness; amplitude is a measure of shortening.

Question 20

Antiforms close _, synforms close _

Answer 20

Antiforms close upwards, synforms close downwards

Question 21

• Anticlines have _ _ in their core; synclines have _ _ in their core

Answer 21

• Anticlines have older layers in their core; synclines have younger layers in their core