Structural

Front 1

What is meant by the expression "non-coaxial" deformation history?

Back 1

Non-coaxial deformation occurs when some or all of the principle stress axes rotate during deformation.

Front 2

If we compress a thick layer and a thin layer so that they start buckling, which layer do you think starts to buckle first?

Which one do you think will thicken most prior to folding?

Which of the two layers will form the largest folds?

Back 2

The thick layers will start to buckle first.

The thick layer will thicken more prior to folding because it experiences a longer period of shortening.

The thick layer will form the largest folds (longest wavelengths, larger amplitudes).

Front 3

What is cleavage refraction and how can we explain it?

Back 3

Cleavage refraction is the symmetrical fanning of cleavage as a result of folding in layers that have a competence contrast. The incompetent layers experience more flexure and "fan" outwards.

Front 4

What makes mullions and buckle folds similar?

Back 4

They each form in/along a competent layer in a less viscous matrix.
They each from from layer parallel shortening.
They each form a specific wavelength based on viscosity contrast.

Front 5

What lineations mark the x-axis of the strain ellipsoid?

Back 5

Strain lineations mark the x-axis of the strain ellipsoid.

Front 6

How can a layer boudinage and fold at the same time?

Back 6

A layer can boudinage at the same time as a fold is tightening, provided the limbs of the layer have rotated into the field of instantaneous stretching.

Front 7

What is meant by the term S-C structures?

Back 7

S-C structures are a composite of foliation (S) and small-scale shear-bands that rotate the foliation relative to the shear direction. The shear-bands form during shearing, and the foliation forms or is modified by the same shearing history (may have also formed before shearing).