Terminology

Question 1

Primary structures

Answer 1

Structures related to sedimentology or igneous processes

Question 2

Secondary structures

Answer 2

Features formed by tectonic processes, e.g., folds, faults, veins, joints, diapirs, etc.

Question 3

Normal faults

Answer 3

Hanging wall moves down + missing section

Question 4

Reverse faults/thrusts

Answer 4

Hanging wall moves up + repeated section

Question 5

Strike-slip faults

Answer 5

lateral/horizontal movements (no hanging wall)

Question 6

Stress

Answer 6

Force per unit area. Stress is a vector, having a magnitude and orientation.

Question 7

Strain

Answer 7

The deformation that results from applied stress

Question 8

Fold limb

Answer 8

Foldesjenkel - “armene” til folden

Question 9

Hinge line

Answer 9

Linjen hvor foldesjenklene møtes

Question 10

Foldeakse

Answer 10

“Enden” på hengsellinjen

Question 11

Fold axial plane

Answer 11

Planet som går gjennom midten til foldesjenklene, kan brukes for å se vergence.

Question 12

Synform

Answer 12

Ukjent stratigrafi, smilefjes

Question 13

Antiform

Answer 13

Ukjent stratigrafi, surt fjes

Question 14

Accretionary orogen

Answer 14

Orogenesis during on-going subduction, can be divided into two types; retreating orogens and advancing orogens.

Question 15

Retreating Accretionary Orogens

Answer 15

• Long term extension in response to lower plate retreat
• Driven by negative buoyancy of down going slab
• Trench rollback
• Develop back-arc basins, upper plate extension
• Rifting of continental ribbons
• Magma can rise directly to the surface (mafic-felsic, bimodal)

Question 16

Advancing Accretionary Orogens

Answer 16

• Overriding plate advances towards the downgoing plate at rate equal or greater than the rate of lower plate slab retreat
• Widespread crustal shortening and uplift
• Resulting in a foreland fold and thrust belt
• Strike-slip motion common
• Subduction erosion: accretionary prism
• Large earthquakes
• Slow magma-rise: since fractures are
closed; causes large fractionation: intermediate to felsic rocks

Question 17

Shear sense indicators

Answer 17

Mica fish, S-C-structures, grain tail complexes; sigma, delta and phi