Geology 312 Final

Front 1

anastomosing fault

Back 1

Faults that are linked to other faults while still active

Front 2

tip line

Back 2

the line at which the fault terminates and displacement decreases to zero

Front 3

hinge line

Back 3

The line of greatest curvature in a folded surface

Front 4

fold axis

Back 4

the surface that when moved along outlines the surface of the fold

Front 5

profile plane

Back 5

the surface perpendicular to the hinge line

Front 6

inflection point

Back 6

the position in a limb where the sense of curvature changes

Front 7

fold crest

Back 7

the topographically highest point of a fold, which need not coincide with the fold hinge

Front 8

fold trough

Back 8

The topographically lowest point of a fold, which need not coincide with the fold hinge

Front 9

limb

Back 9

Less curved portion of a fold

Front 10

cylindrical surface

Back 10

Fold in which straight hinge line parallels the fold axis

Front 11

antiform

Back 11

A formation where the hinge zone is at the top (looks like a mountain)

Front 12

synform

Back 12

A formation where the hinge zone is at the bottom (looks like a valley)

Front 13

synformal anticline

Back 13

A formation where the hinge zone is at the bottom, however the oldest rocks are in the middle.

Front 14

facing

Back 14

the direction of younging alone the axial plane

Front 15

enveloping surface

Back 15

the imaginary plane that is tangential to the hinge zones of a series of small folds in a layer.

Front 16

parasitic fold

Back 16

minor folds often found in thinner layers (used to describe shape of large scale folds by drawing envolping fold)

Front 17

vergence

Back 17

direction in which fold turns

Front 18

monocline

Back 18

fold structures with only one tilted limbs; the beds on either side of the tilted limb are horiztonal

Front 19

doubly plunging fold

Back 19

structures with hinge lines that laterally change curvature.

Front 20

anticlinorium

Back 20

regional scale antiformal fold, usually made up of many smaller folds

Front 21

synclinorium

Back 21

regional scale synformal fold, usually made up of many smaller folds

Front 22

recumbent fold

Back 22

a fold with a horizontal axial surface that has a horizontal hinge line

Front 23

kink folds

Back 23

angular fold with a kink plane and a kink axis. They are small fold characterized by straight limbs and sharp hinges

Front 24

chevron folds

Back 24

fold that have angular hings and limbs of approximately equal lenths. They are the large scale equivalent of kink folds.

Front 25

box folds

Back 25

Tow kink bands inclined to each other

Front 26

pytgmatic folds

Back 26

irregular and isolated fold structures that typically occur as tightly folded veins or thin layers of strongly contrasting lithology.

Front 27

sheath folds

Back 27

Shows extreme hinge line curvature ( folding of a fold)

Front 28

fault-bend folds

Back 28

formed as thrust sheets move over ramps

Front 29

fault propagation folds

Back 29

accommodation strctures above the frontal tip of a thrust

Front 30

orthogonal flexure

Back 30

the way the bed folds that keeps all the fold perpendicular to the folding angle

Front 31

How do faults end?

Back 31

Faults terminate where cut by younger structuers (faults, unconformity, intrusions). They can move into splays, die out,

Front 32

splay

Back 32

a principal fault from which many smaller faults diverge

Front 33

What structures form when a faults end?

Back 33

Horsetail, emergent fault (fault is still active when it hits surface), exhumed fault (fault is inactive and is eroded to surface), blind fault ( never sees surface)

Front 34

How do you determine the relative age of a fault?

Back 34

by finding a marker bed and measuring the difference between them.

Front 35

What characterizes a region where the structure is dominated by extensional faults?Contractional faults?

Back 35

Extensional (lengthening of layers, loss of stratigraphic section, normal faults)
Contractional faults (shortening of layers, duplication of strigraphic section, reverse and thrust faults)

Front 36

What is a basal detachment?

Back 36

The area where a series of ramps merge at depth.

Front 37

What is a thrust fault?

Back 37

a reverse fault with a very low dip angle

Front 38

What types of fold are associated with thrust faults?

Back 38

fault bend folds

Front 39

What is the difference between an imbricate system and a duplex system?

Back 39

An imbricate systems consists of thrusts that either intersects the ground surface or die out up dip, whereas a duple consists of thrusts that span the interval of rock between a higher level detachment called a roof thrust and a lower level detachment called a floor thrust.

Front 40

What are the different types of structures formed in duplex systems?

Back 40

Hinterland-dipping duplex
antiformal stack
foreland dipping duplex

Front 41

What influences which type of duplex structure forms?

Back 41

The difference between the duplex system is the amount of displacement per fault/fold section

Front 42

What is the difference between passive folds and flexure folds

Back 42

Passive folding: the strata appear shifted undistorted, assuming any shape impressed upon them by surrounding more rigid rocks. The strata simply serve as markers of the folding
Flexure folds : the presence of layers with different competency directly affects the strain pattern in the deforming body and that there is constrasting behavior between layers

Front 43

What type of strain does flexure folding accomplish?

Back 43

It goes through either bending or buckling

Front 44

What data would you collect to describe a fold in an outcrop?

Back 44

interlimb angle
hinge shape
limb shape
fold system
symmetry of fold system
orientation

Front 45

Why is it important to consider the profile plane?

Back 45

It allows you to find the fold orientation.

Front 46

What can you learn from z or s folds?

Back 46

Which side of the fold that you're on.

Front 47

What are the 4 components that fold classification is based on?

Back 47

cylindrical vs non cylindrical
antiform vs synform
fold orientation
fold shape

Front 48

What is the difference between parallel folds and similar folds?

Back 48

successive bedding planes remain parallel in parallel folds while in similar fold thickness parallel to the axial trace remains constant.

Front 49

What are bending and buckling?

Back 49

Bending and buckling are ways of deforming a rock by folding. Buckling the force is oriented parallel to the mechanical anisotropy. Bending the applied force is oriented at an oblique angle to the layering.

Front 50

Do all layers behave the same way around a fold?

Back 50

No, the mechanical properties of each layer determine how the layers will fold

Front 51

How do layers move relative to one another?

Back 51

They slip in most cases or flow

Front 52

What structures accommodate flexure?

Back 52

outer arc extension (fractures/vains)
inner arc contraction (small faults/cleavage/styolites

Front 53

How does layering influence flexure folds?

Back 53

Rock type influences the shapes of olfds
layer thickness influneces the shape and size of folds
regional

Front 54

What structures form to accommodate this strain and what is the spatial distribution of these structures around a fold?

Back 54

Bulbous hinges
limb thrusts
boudinage of limb

Front 55

Does passive folding neccessarily accommodate shortening?

Back 55

NO

Front 56

Does passive folding create similar or parallel fold? flexure?

Back 56

Similar = parallel
Parallel = flexure

Front 57

fabric

Back 57

geometric configuration and distribution of the component parts of a rock

Front 58

foliation

Back 58

a planar fabric in rocks (fabric elements are or somehow define surfaces)

Front 59

lineation

Back 59

a linear fabric in rocks (fabric elements are or somehow define lines)

Front 60

Cleavage

Back 60

a secondary fabric element formed under low temperature conditions, that imparts to the rock a tendency to split along planes.

Front 61

primary fabric

Back 61

the fabric elements are original constituents of a rock and their arrangements result from processes that operate during the formation of that rock

Front 62

crenulation cleavage

Back 62

a lithology containing a closely and evenly spaced foliation that is shortened in a direction at a low angle to this foliation will crinkle like the baffles in an according. The axial planes of the crenulations are crenulation cleavage

Front 63

What is the difference between kink folds and chevron folds?

Back 63

Chevron folds are on a much larger scale than kink folds and have two limbs that are often symmetrical. Kink folds are much smaller in terms of scale with one limb that is larger than the other.

Front 64

During buckling, how does mechanical anisotropy influence?

Back 64

With increasing thickness, the arc length and wave length become larger.
With layers that have differing strength, the arc length of the stronger layer is larger than the weaker layer.
With layers that have differing viscosity, the greater the difference the more compressed the rock becomes.
With

Front 65

What is the difference between primary and secondary fabrics? Give an example of each

Back 65

Primary fabrics (foliation/lineation)formed during the formation of that rock while second fabrics (cleavage/schistosity) formed due to deformation/metamorphism.

Front 66

fabric elements

Back 66

the features of a fabric (mineral grains, clasts, compositional layers, fold hinges, planes of parting)

Front 67

What is the difference between a penetrative and non-penetrative fabric? How are they defined?

Back 67

A penetrative fabric is a rocks whose internal structure has been substantially changed during defomration. The fabric is defined by grains that have been partially or totally recrystallized, and/or by new minerals that have grown during deformation. While non-penetrative fabrics have not been change substantially during deformation.

Front 68

How do flexure fold often initiate?

Back 68

Through buckling or bending

Front 69

What are the relationships between flexure folding, passive folding, parallel folds and similar folds? How common are each in nature?

Back 69

Flexure folding creates parallel folds and passive folding creates similar folds. Parallel and similar folds are very uncommon in nature because it is rare to get perfect formations

Front 70

Different fabric elements form different types of foliations and lineations. Describe both the fabric elements and the types of fabrics they form.

Back 70

Foliations are usually formed by the preferred orientation of minerals within a rock.
Lineations are formed with the deformation of the rock.

Front 71

How might an axial planar cleavge form?

Back 71

It is generally assumed that the cleavage formed roughly synchronous with folding and is subparallel ot the XY plane of the bulk finite strain ellipsoid.

Front 72

How can you use cleavage to determine where you are along a fold?

Back 72

Crenulation Cleavage is symmetrical when it is near the hinge and asymmetric on the limbs