يزاقاب دمحم نب مثيه سيردتلا ةئيه وضع · WHY STRUCTURAL GEOLOGY IS...

transcript

hbagazi@kau.edu.sa

+966540084084

hbaggazi

هيثم بن محمد باقازيكلية علوم األرض بجامعة الملك عبدالعزيز–عضو هيئة التدريس

- Control the migration, trapping and escape of

hydrocarbon fluids

- Guide the mining process

- Interpretation of geophysical, geochemical, and

geochronological data.

- Geotechnical site assessment for bridges, dams,

tunnels, nuclear reactors, waste disposals etc.

- Earthquake seismology.

- study of past and present mountain belts and

sedimentary basins

WHY STRUCTURAL GEOLOGY IS IMPORTANT

Haitham Baggazi, 2020

St#DD_Lat

DD_Long

Strike

121.54

13339.62

508 10

221.54

41139.62

472 310

221.54

41139.62

472 130

521.55

39439.62

611 310

Recognizing and describing structures and measuring:

locations, geometries, and orientation

Examples: Orientations of bedding and foliations - Positions of fold hinges and faults

St#DD_Lat

DD_Long

Strike

121.54

13339.62

508 10

221.54

41139.62

472 310

221.54

41139.62

472 130

521.55

39439.62

611 310

Deformational movements responsible for the development of the structures

Rotation - changes in orientation

Dilation - changes in sizeDistortion - changes in shape

Translation - changes in position

Examples: How far did this fault slip - How much shortening occurred Haitham Baggazi, 2020

Forces or stresses responsible for the formation of structures

(Stress Analysis)

Examples: How much stress is acting on the San Andreas fault - What drives plate movements?

Abdullah et. Al., 2014Baggazi et. al., 2019

Baggazi, 2020 Baggazi, 2020

Global Scale Structures(Geotectonics)Non-Tectonic Structures

(Primary Structures)

Tectonic Structures(Secondary Structures)

❖Primary Igneous❖Intrusive and Extrusive❖Primary Sedimentary

Brittle Structures

Folds, Foliations, Lineations Faults, Joints

❖History❖Plate Tectonic Theory❖Plate Boundaries

Ductile Structures

Top and bottom of the

stratigraphic sequences

http://www.wenval.cc/rdawes/http://www.travelinggeologist.com/2012/09

http://www.volcano.si.edu http://marlimillerphoto.com/intrusive.html

http://serc.carleton.edu http://raider.mountunion.edu

http://users.monash.edu.au

Figure 35. Mineral cluster lineation plunging south (looking West).

Figure 36. Horizontal mineral cluster lineation in medium to high schistose

metamorphic rocks (looking West).

http://notnecessarilygeology.wordpress.com

http://raider.mountunion.edu

Stress-Related Structures

• Tensional stress: pulling apart, extension,

stretching (Normal fault, rift)

• Compressional stress: pressing together

(Fold, reverse fault, thrust fault)

• Shear stress: Strike-slip fault

• Vertically directed stress: Stress up or

(down Uplift – dome, Subsidence – basin)

Brittle Behavior – Near the Earth’s surface (low T and P), rocks exhibit brittle behavior.

Ductile Behavior – At depth in the Earth (high T and P), rocks exhibit plastic behavior.

http://3dparks.wr.usgs.gov/nyc/highlands/highlands.html

http://www.teachengineering.org/

• Hinge Line (fold axis): “intersectionbetween axial plane and the bed”.And “ it is the line in the foldedsurface along which the curvature isa maximum” (Twiss and Moores1992).

• Limbs “ are the flanks of folds >>joined at the hinge” (Davis andReynolds, 1996) and “ regions withlowest curvature” (Twiss andMoores, 1992).

• Axial surface “ passes throughsuccessive hinge lines in a stackingof folded surfaces.., Planner axialsurface is called axial plane” (Davisand Reynolds, 1996).

• Hinge Zone “ Maximum curvatureachieved along the folded surface” (Ramsey, 1967, and Davis &Reynolds, 1996). “ most highlycurved portion of a fold near thehinge line” (Twiss and Moores,1992).

Davis and Reynolds, 1996Haitham Baggazi, 2020

Pluijm and Marshak, 2004

http://homepage.usask.ca

http://www.see.leeds.ac.uk

Pluijm and Marshak, 2004

http://www.rci.rutgers.edu

http://www.ualberta.cahttp://www.rci.rutgers.edu

Davis and Reynolds, 1996

http://www.eas.purdue.edu/

http://www.elateafrica.org/elate/geography/earthmovements/earthmovementsintro.html

http://www.ualberta.ca

Symmetrical FOLD

Asymmetrical FOLD

- Fold

- Anticline Fold

- Tight Anticline Fold

- Open Syncline Fold

- Anticline plunging Fold

- Tight- Plunging anticline fold

- Tight – North Plunging – Anticline Fold

- Isoclinal – Inclined – North Plunging- Anticline fold

- Tight – Inclined- Asymmetrical – north plunging - anticline fold

- Tight – incline – South Verging- Asymmetrical – North Plunging- Anticline fold

Baggazi, 2020

Fold vergence

The rotation of the axial surface from the symmetric fold style

into the asymmetric style. The vergence trend indicates to the

direction of tectonic stress formed these folds.

In the areas that affected by two or more folding phases, the folds

show simple or complex interference patterns depending on the

orientations of the two folding phases.

Interference patterns

Baggazi, 2020

Baggazi, 2020Haitham Baggazi, 2020

Outcrop belts formed on the limbs of plunging folds tend to

converge and form a "U" shaped pattern. This "U" points or

converges in the direction of plunge in anticlines, but opposite to

direction of plunge in syncline

http://hays.outcrop.org/GSCI100/lecture14s.html

A is the trend of the fold axis

http://web.arc.losrios.edu/Haitham Baggazi, 2020

Anticline

Always verge toward the anticlinal hinge. When you see a small asymmetric fold, you

can infer that there is a larger fold with an anticlinal hinge in the direction of the vergence.

https://www.geological-digressions.com/s-and-z-folds/Haitham Baggazi, 2020

Faults

Anderson theory

Anderson’s Standard relationship between ideal faults and stresses

Faults

Baggazi, 2020

Faults

F.WF.W

F.W F.W

Faults

Rake = 50 from N

Faults

Baggazi, 2020

Baggazi, 2020 Baggazi, 2020Baggazi, 2020

A good structural geologist

• The ability to think in 3D and to solve large scale 4D puzzles.

• The ability to interact with a large range of geoscientists over a wide range of geological and environmental problems.

• The ability to link field studies to computationalmodelling.

يزاقاب دمحم نب مثيه سيردتلا ةئيه وضع · WHY STRUCTURAL GEOLOGY IS...

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