The Beauty of Geologic Structures

8/8/2019 The Beauty of Geologic Structures

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The Beauty and Economic

Significance of Geologic Structures


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Why study geologic structures?

1992 Landers, CA Earthquake (photo by Ramon Arrowsmith)


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Understand and anticipate natural hazards (1995 Kobe Earthquake):(Slide by Ramon Arrowsmith)

http://www.ngdc.noaa.gov/seg/hazard/slideset/21/21_slides.shtml


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Mineral resourcesMineral resourcesEnergy &Energy &Mineral resourcesMineral resources

Magmatic segregation: gems in pegmatites:

Hydrothermal solutions: important for concentating

and precipitating ore deposits:Hot, metal-rich fluid migration as vein deposits or

disseminated deposits (remobilized by faults)

Crystallization in fluid-rich environment

(Quartz

Veins)

(modified from slide by Ramon Arrowsmith)


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Mucho oro! Mucho dinero!!


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Los ncleos de perforadora diamante a la

Zona Azul, Proyecto Len


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Types of oil traps

(Keller, 2002)


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Primary Geologic Structures

Geometric features developed during

formation of a rock body

Microscopic to mountain scale Formed in sedimentary or igneous

environments

P

rovide clues about environmentof rockformation


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Sedimentary Structures

Bedding

Uncomformities

Cross bedding Graded bedding

Ripple marks

Mud cracks

Trace fossils

Etc.


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Bedding(stratificacin)

in the Grand

Canyon (Can

Grande):Sediments originally

deposited in horizontal

orientation

Superposition: oldest

layers on the bottom,youngest on top

Major bedding planes

separate sedimentary

layers with contrasting

properties (strength,

porosity, permeability,resistance to erosion, etc)


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Tilted bedding in Hawk Canyon (Caada Halcn), December, 2008


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Tilted bedding on San Miguel Island, May, 2004


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Tilted bedding on San Miguel Island, May, 2004


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San Miguel Island, May, 2004


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San Miguel Island, May, 2004


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Angular unconformity on San Miguel Island, May, 2004


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Nonconformity in Caada Halcn, February, 2007


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Tilted nonconformity, Caada Halcn, February, 2007


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Proyecto Len, Marzo, 2007


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Proyecto Len, Marzo, 2007 (cross beds deposited originally non-horizontal)


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Algadones Dunes (las dunas Algadones), January, 2007


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Which way is the wind blowing?


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Igneous Structures Flows

Veins

Dikes and Sills

Chilled or baked margins Magmatic flow foliation

Flow tops marked by vesicles

Aa-aa vs. pahoehoe structure Stocks and batholiths

Xenoliths or inclusions

Magmatic segregations


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Originally non-horizontal lava flow at Cerro Los Ojos, Sonora


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Originally non-horizontal lava flow near Sierra Chocloduro, Sonora


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Grand Canyon (photo by Ramon Arrowsmith)


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San Antonio Canyon,

March, 1998


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Sierra la Salada, Marzo, 2007


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Glendora Ridge Road, October, 2006


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Culp Valley, November, 2007


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Proyecto Colibri,

Marzo, 2006


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Zona Nopal,

Deciembre, 2006


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Mucho oro!


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Este oro es mio!


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Mis asistentes

del campo,

Proyecto Len,Septiembre, 2007


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Proyecto Len,

Septiembre, 2007


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Proyecto Len,

Marzo, 2007


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Mas ncleosde perforadora diamante a

la Zona Azul, Proyecto Len


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Folds

Photograph courtesy of Ramon Arrowsmith


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Prince William Sound, Alaska, July, 2006


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Prince William Sound, Alaska, July, 2006


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Palmer Canyon, San Gabriel Mountains, December, 2004


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Palmer Canyon, San Gabriel Mountains December, 2004


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Coastal Maine, July, 2007 (photo by Kayla Kroll)


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Coastal Maine, July,

2007 (photo by Kayla

Kroll)


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Proyecto Colibri, Marzo, 2007


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diagram from M.P. Searle

Faults (mountain scale)

Faults (mountain scale)


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What is it?

Moab normalfault, Utah

(Slide courtesy of

Greg Davis)


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Whipple detachment fault, California (Slide from Greg Davis)


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Younger on older, Low-grade (near surface) on High-grade (12 km)

Ertomiao detachment fault, Lang Shan, ChinaErtomiao detachment fault, Lang Shan, China

(Slide from Greg Davis)


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1 horizontal, 3 vertical reverse faults

1 vertical, 3 horizontal normal faults 1 horizontal, 3 horizontal strike-slip

faults

(Slide designed by

Greg Davis)


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Hypothetically

Reverse faults: should form at ~30 dip

Normal faults: should form at ~60 dip

Strike-slip faults: should form at ~90 dip

Can you think

of any

exceptions??

(Slide designed by Greg Davis)


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Common exceptions Thrust faults mechanically unfavorable

Low-angle normal faults mechanically

veryunfavorable

(Slide designed by Greg Davis)


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Faults and Breccias at Outcrop

Scale

Manker Canyon, San Gabriel Mountains, October, 1994


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Falla normal a

Caada Halcn,

Deciembre, 2008


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Mega Faults

Sonoyta, Sonora,

Jenero, 2006


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Sonoyta, Sonora, Jenero, 2006


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Sonoyta, Sonora, Jenero, 2006


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Proyecto Ramaje Ardiente, Marzo, 2007


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Proyecto RamajeArdiente, Marzo, 2007


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Proyecto RamajeArdiente, Marzo, 2007


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Proyecto Ramaje Ardiente, Marzo, 2007


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Proyecto Colibri, Jenero, 2006


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Proyecto Colibri, Jenero, 2006


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Zona Nopal,

Deciembre, 2006


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Zona Nopal,

Deciembre, 2006


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Zona Nopal, Deciembre, 2006


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Proyecto Elizabeth, Octubre, 2008


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Proyecto Elizabeth,

Octubre, 2008


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DiamondDrill

Core from the

Naranja Zone


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Mylonites and Ductile Shear Zones


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Foliation

Planar fabric formed by ductile flow of

minerals under directed stress

Generally manifested as compositional

layering

Foliation plane generally oriented at high

angle to maximum stress direction


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San Gabriel Mountains, April, 2002


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San Gabriel Mountains, April, 2002


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Arroyo Santa Felicita, Noviembre, 2008


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Lineation


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What is the sense of shear?


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What is the sense of shear?

(Slide from Greg Davis)

Just how deformed is this rock?


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Just how deformed is this rock?

(Slide from Ramon Arrowsmith)

Or this one?What % extension has this rock experienced?


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Or this one?What % extension has this rock experienced?

Documents

The Beauty of Geologic Structures