Lecture 13-14 - Landscape and reverse faults

Question 1

How do thrust faults appear in mountain belts such as the Himalayas?

Answer 1

Thrust fault dips in the same direction as the subduction zone but mountains grow in opposite direction

Question 2

Describe coseismic and interseismic deformation and what effect does this have on geological structure? (Graphs)

Answer 2

Question 3

How do thrust faults co-seismic and inter-seismic deformations appear?

Answer 3

Co-seismic is the opposite of a normal fault and inter-seismic is not known.

Question 4

Where are thrust and fold belts found?

Answer 4

Found everywhere in the modern and geologic record. Examples are Himalayas, Western foothills of Taiwan and the Jura Mountains in the Alps

Question 5

How do fold thrust belts form?

Answer 5

Fault bend fold model

Question 6

What do we need to test the fault bend fold model?

Answer 6

Methods that can be used:

• over Myr time scale
• record ecolution of the crust
• work well with high uplift
• sensitive at depths of <10km

Question 7

What is thermochronology?

Answer 7

Thermal history of rocks. Measures cooling history of rocks. Their trajectory to surface = denudation

Question 8

What needs to be measured in thermochronology?

Answer 8

A daughter product and parent nuclides whose decay generated the daughter. The more daughter the more time has passed.

Question 9

How are fission tracks measured?

Answer 9

The daughter are crystallographic damage zones called fission tracks, produced by the relatively rare but energetic spontaneous fission of ²³⁸U

Question 10

What are the closure temperatures for Apatite (U-Th)/He, Apatite fission tracks and Zircon (U-Th)/He?

Answer 10

• Apatite (U-Th)/He: 70 degrees
• Apatite fission tracks: 120 degrees
• Zircon (U-Th)/He: 180 degrees