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Announcements. Reminder, this Saturday field trip . Meeting place/time: GS loading dock at 7:45 am. Bring hiking gear, lunches, water.

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Announcements

Reminder, this Saturday field trip . Meeting place/time: GS loading dock at 7:45 am. Bring hiking gear, lunches, water.

Extra credit: get 1 point (test-equivalent; for each tectonics -related Geoscience colloquium attended between now and end of class). A list of colloquiums to attend will be posted on the web. Turn in a paragraph summarizing the main points of the talk.


Normal faults

-rifted continental margins

-form in extension

-typical for continental and oceanic lithosphere

-jargon (horsts, grabens, listric, detachment)

-are they low-angle?

-core complexes

-Example: Basin and Range, -the way we think it works, mechanically

-

Normal fault systems(D&R: 340-357)


Can you spot the fault?


It’s low angle, but so are thrust faults:

KEY: puts young (hanging wall) on old

(footwall). The fault markers (slickenlines

Etc) are the same.


Horsts and grabens

Iin agreement with Coulombian mechanics


Some problems with the model-

Most faults look listric and low angle

Listric


Pure shear or simple shear??


Simple shear

A complication of simple shear


How do extensional faults look like?


Sedimentation takes place during faulting;

Also block rotation domino-style


Cottonwood Canyon - this Saturday’s trip


Figuring out timing of extension: 1. Magmatism

2. Sedimentation


High angle faults are present too- East African rift large scale example

Moab fault


Basin and Range- world’s

most studied extensional

province-low-angle normal

faulting prevails.


How do continents break apart?


A view of the Mountains north of us… the Catalinas


Core complexes- metamorphic core


Exhumation of metamorphic cores beneath detachment faults

Extension of the upper crust commonly requires flow in the mid- to low crust and/or magmatic additions


Important things about normal faults.

1. Fundamental to structure of continents and oceans.


Important things about normal faults.

2. Two different styles: the low-angle and high-angle.


Important things about normal faults.

3. Can take up as much extension as compressional

orogens shorten.


Important things about normal faults.

4. You live in the most famous (and perhaps

most important extensional region-the B&R).


Important things about normal faults.

5. Extension is accompanied by big-time

sedimentation-important for oil formation.


Important things about normal faults.

1. Fundamental to structure of continents and oceans.

2. Two different styles: the low-angle and high-angle.

3. Can take up as much extension as compressional

orogens shorten.

4. You live in the most famous (and perhaps

most important extensional region in the world-the B&R).

5. Extension is accompanied by big-time

sedimentation-important for oil formation.


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