Lecture 1: Folds (I) Flashcards
-Linear features are measure by
trend and plunge
Geological surfaces are measured by-
- Strike,
- dip and
- dip direction
Fold angularity MUST be made when looking through the
Profile Plane.
MUST look _ _ _ in order to identify if its an _ or _ fold
MUST look down the plunge in order to identify if its an S or Z fold
One common occurrence of S and Z folds, is when folds occur at _ scales in _ layer
One common occurrence of S and Z folds is when folds occur at different scales in the same layer
Small folds developed on the limbs of larger folds, with the same orientation, are called _ _
parasitic folds
Typically, parasitic folds on one limb have _ asymmetry whereas those on the other limb have _ asymmetry
Typically, parasitic folds on one limb have S asymmetry whereas those on the other limb have Z asymmetry
There is often a region on the _ where parasitic folds have no _ _ ; they are described as _ (or _ ) folds.
There is often a region on the hinge where parasitic folds have no clear asymmetry; they are described as M (or W) folds.
Sometimes mapping the asymmetry of outcrop-scale parasitic folds is a good way to locate the _ of less obvious map-scale major folds.
Sometimes mapping the asymmetry of outcrop-scale parasitic folds is a good way to locate the hinges of less obvious map-scale major folds.
The smaller hinges on the parasitic fold are _ to that of the _ fold. What does this tell us? _ _ _ _ _ _ _
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.
folds where each layer is folded in step with the adjacent layers. These are called _ folds
folds where each layer is folded in step with the adjacent layers. These are called harmonic folds
Sometimes we find layered rocks in which the folds are not so aligned. These are _ folds.
Sometimes we find layered rocks in which the folds are not so aligned. These are disharmonic folds.
There is a relationship between the thickness of the layer and the wavelength of fold produced-
The thinner the layer the thinner the fold length. The thicker the layer the larger the fold length
_ form when layered materials are deformed
Folds form when layered materials are deformed
The orientation of folds must be described by: _ _and _ of the _.
and the _ / _and _ _ of the _ _
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
Kink Bands have _ hinges and _ limbs: they form in _ rocks. Intersecting kink bands from _ _
Kink Bands have angular hinges and straight limbs: they form in anisotropic rocks. Intersecting kink bands from box folds
Asymmetric folds should be described as S or Z looking _ _
Asymmetric folds should be described as S or Z looking down plunge
Parasitic folds are _ or _ order folds (smaller _ and _) that occur on:
The _ of _ or _ order folds. They are commonly _.
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.
Fold wavelength and amplitude should be estimated. Fold wavelength depends on layer _; amplitude is a measure of _.
Fold wavelength and amplitude should be estimated. Fold wavelength depends on layer thickness; amplitude is a measure of shortening.
Antiforms close _, synforms close _
Antiforms close upwards, synforms close downwards
- Anticlines have _ _ in their core; synclines have _ _ in their core
- Anticlines have older layers in their core; synclines have younger layers in their core
