Structural geology exam 2

Know diagram of the geometry of a fold

Know where hinge line is

Understand the difference between straight and curved hinge lines

Know veins

Tightness of hinge fold levels

Gentle: 180-120,

Open: 120-70

Close: 70-30

Tight: 30-5

Isoclinical: <5-0

Antiform & Synform also work as natural resource traps

know basic fold shapes

Know young/old movement of anti/syncline

Ramsey’s 1967 classification based on dip isogon

Understand symmetric and assymentric folds

M-fold - symmetric

Z-fold

S-fold - Assymetric

fold vergence

upright, inclined, overfold, recumbent

Difference between polyclinal fold

disharmonic fold

harmonic fold

Strain various definitions

pure, simple, and sub-simple shear

displacements fields

Strain formulas

Strain ellipsoid

e1 - longest stretch along x axis

e2 - intermediate, along y axis

e3 - shortest, along z axis

Deformed and undeformed

strain markers in fossils

Understand depth and tectonic deformation based on rock

rock cleavage

different types

Lineations

Ductile vs brittle deformation

Shear zones

Shear zone growth type, 1, 2, 3, 4

porphyroclast symptoms - sense of shear direction

Rotation -

Translation -

Internal deformation occurs

All points move in the same direction by the same amount, no internal deformation

Homogeneous strain

Lines that are straight and parallel before deformation remains straight and parallel after deformation.

Heterogeneous strain

Lines that are straight and parallel before deformation are no longer straight and parallel.

Boudin and pinch and swell structures are controlled

by temperature, strain rate, competency or viscosity