Questions and Answers of Structural Geology

What is the difference between a slip plane in a plastically deforming crystal and a slip plane associated with brittle faulting?
What are the principal differences between brittle and plastic deformation?
Why is intracrystalline fracturing so common in brittle deformation of highly porous rocks?
Name two plastic deformation mechanisms that can operate at shallow crustal depths.
What is meant by the term dislocation creep and how does it differ from diffusion?
What deformation mechanism is particularly active in finegrained rocks at high temperatures (in the lower crust and the mantle)?
What information can we get from dynamically deformed quartz that disappears during static recrystallization?
What is the difference between recrystallization by subgrain rotation and grain boundary migration?
Make a sketch map of a dome, a basin, an upright synform and a plunging upright synformal anticline.
How could dome-and-basin patterns form?
How can we distinguish between flexural flow and orthogonal flexure?
How would we identify a buckle fold?
A shear fold?
What is the difference between a parallel and a similar fold?
What fold types are parallel?
Where can we expect to find similar folds?
In what settings do monoclines typically form?
If we compress a thin layer and a thick layer so that they start buckling, which layer do you think starts to buckle first?
Which one do you think thickens the most prior to folding?
Which of the two layers would form the largest folds?
What conditions give more or less concentric and parallel folds?
How can dip isogons help us distinguish between buckle folds and shear folds?
What is the difference between primary, secondary and tectonic foliations?
How are primary foliations recognized in deformed and metamorphosed sedimentary rocks?
What separates a fracture zone from a cleavage or foliation?
What type of strain can produce transected folds?
What favors the formation of continuous (dense) cleavage?
What is the most important mechanism for cleavage formation?
What is meant by QF- and M-domains?
What is cleavage refraction and how can we explain it?
How can we use the angle between cleavage and a precleavage foliation to predict large-scale fold geometry?
Why is cleavage always associated with flattening strain(oblate strain ellipsoids)?
What is the difference between shear bands (extensional crenulation cleavage) and ordinary crenulation cleavage?
What makes mullions and buckle folds similar?
What types of lineations form in the brittle regime?
What lineations mark the X-axis of the strain ellipsoid?
What type of lineation can be related to ISA1?
How do striations or slickenlines relate to kinematics?
What is the difference between crenulation lineations and intersection lineations?
How do boudins relate to the strain ellipsoid?
How do mineral lineations that form in the brittle and plastic regime differ?
Why must we have a strain model when considering the relationship between stretching lineation and transport direction?
How are the various lineations defined and how do they develop?
What is the difference between classic and foliation boudinage?
How can a layer fold and boudinage (extend) at the same time?
Why do pinch-and-swell structures sometimes develop instead of boudins?
Where is stress concentrated in classic boudins?
Why are boudins and pinch-and-swell structures less common than folds in deformed metamorphic rocks?
Do rotated boudins imply non-coaxial deformation?
What does chocolate tablet boudinage tell us about the strain field?
Why are folded boudins indicative of two phases of deformation?
Are there cases where folded boudins can form during progressive deformation?
What makes a shear zone different from a fracture?
Can you draw the upper shear zone margin on Figure 16.9?Is it easily definable?
What type of data support the idea that shear zones grow in width as they accumulate displacement, and where would we look for the last increment of strain?
What assumption do we have to make for the last increment of strain to be representative of earlier strain increments in the zone?
What is meant by the term S-C structures?
What do you think are the most and least reliable shear sense structures described in this chapter?
How could you get information about the strain path (strain evolution) of a shear zone?
What are branch lines and how could they be useful?
If you were looking for oil, what type of contractional structure covered in this chapter would you look for?
What is meant by a mylonite nappe?
What is the difference between a fault-propagation fold and a fault-bend fold?
Where could we expect to find back-thrusts?
What is the ideal setting for detachment folds to form?
How can extensional faults form in a thrust-and-fold belt?
What conditions determine the shape of an orogenic wedge?
How can those conditions change during an orogenic event?
Why is it likely to have preexisting normal faults in an orogenic belt?
How can a reverse fault in some special cases also be extensional?
What is unrealistic about the domino fault model?
How can low-angle faults form if we expect normal faults to form with dips around 60°?
Give at least two examples of fault development that create domino-like fault blocks but contradict the domino model.
Explain the formation of an extensional fault set that overprints earlier extensional faults formed during the same extensional phase.
In what settings can metamorphic core complexes form?
What is meant by the rolling hinge mechanism during extensional detachment faulting?
Why does crustal balancing yield different estimates of extension than summing fault heaves across many rifts?
What may cause the entire orogen to uplift during or at the end of the collisional history?
What are the characteristics of large-scale strike-slip faults or shear zones?
What is the role of transfer faults and in what settings do they occur?
What type of structures form where a strike-slip fault makes a stepover or an abrupt bend?
What would a profile look like across a restraining bend?Releasing bend?
What type of setting does Death Valley represent?
What could happen to strike-slip faults at depth?
How would you explain flattening strain in a shear zone with a clear strike-slip offset?
Like Death Valley, the Dead Sea is a place where you can walk on dry land below sea level, and an apparently unmotivated “hole in the ground” along a strike-slip fault. How do you think it formed?
How can strike-slip faults accommodate large-scale pure shear?
Why does diapirism not initiate as a result of density inversion alone?
What is meant by reactive diapirism and in what tectonic regime(s) can it occur?
What is it about classic centrifuge models that in some way makes them unrealistic?
What is the difference between active and passive diapirism and how can we distinguish between them?
What is meant by the expression “downbuilding”?
Why do we not see diapirs in the upper part of a gravitydriven décollement setting such as shown in Figure 20.24? Sedimentary loading Extension Dcollement Rafting Salt rollers Diapirism med en
What determines whether a salt wall or salt diapir forms?
What is the difference between a salt sheet and a salt canopy?
What is the effect of a basal salt layer in an orogenic wedge?
Can you do a rough interpretation of Figure 1.6 and identify the stratigraphic level of the salt, pencil in salt structures and interpret the folds? -TW 56 Vers 246 800 6th One DON Dom Dog Dm 30 Sto
What are the two most basic conditions that must be fulfilled for section balancing to make sense?
What is the difference between restoration and forward modeling?
What is meant by ductile strain in restoration?

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