1. GLG310 Structural Geology

2. Announcements Reminder: Application exercise on Tuesday, Sept. 17 in class How do videos look and work? Homework questions? 15 January 2016GLG310 Structural Geology

3. Strain and deformation Stretch (strain) ellipse Rotation of lines in deformation Pure and simple shear Progressive deformation Deformation by change of volume 15 January 2016GLG310 Structural Geology

4. 15 January 2016GLG310 Structural Geology Moving from 1 to 2 to 3 dimensional deformation E and s as we have defined them in the last two lectures are 1 dimensional (measured along l f ). In a deformed material; however, we can define the minimum and maximum stretches and they will be perpendicular S min =l fmin /l 0 S max =l fmax /l 0 l0l0 l0l0 l fmax l fmin

5. 15 January 2016GLG310 Structural Geology Principal stretches Sphere Ellipsoid In 3D, S 1 is max, S 3 is min, and S 2 is intermediate Cube Prism

6. 15 January 2016GLG310 Structural Geology Deformed trilobites do exist! Draw the stretch ellipse for each

7. 15 January 2016GLG310 Structural Geology

9. Angular shear

10. 15 January 2016GLG310 Structural Geology

11. 15 January 2016GLG310 Structural Geology

12. “Coaxial deformation”: Lines parallel to principle axes do not rotate “Pure Shear”

13. 15 January 2016 “Non-Coaxial deformation”: Principle axes are constant but lines rotate with progressive deformation “Simple Shear”

14. Progressive deformation

15. Cloos’ strain study

16. GLG310 Structural Geology Measured stretch ratios in rocks from around the world “Flattening” More common “Constriction” -Suppe, 1985

17. Deformation by loss of material -dissolution -”styolites” http://www.earth.lsa.umich.edu/~vd pluijm/animations/stylolite.mov http://www.geol.umd.edu/~jmerck/geol100/images/15/stylolite.jpg

18. 15 January 2016GLG310 Structural Geology Stylolite: Wave-like or tooth-like, serrated, interlocking surfaces most commonly seen in carbonate and quartz-rich rocks that contain concentrated insoluble residue such as clay minerals and iron oxides. Stylolites are thought to form by pressure solution, a dissolution process that reduces pore space under pressure during diagenesis. Schlumberger Oilfield Glossary http://www.glossary.oilfield.slb.com/Display.cfm?Term=stylolite

19. http://www.asaa.com.au/publicati ons/magazines/DS16_DrDripston eStylolites.pdf

20. 15 January 2016GLG310 Structural Geology

21. Progressive strain History of regional deformation in southern Arizona

22. Stretching and Shortening working together in partnership -Pollard and Fletcher, Fundamentals of Structural Geology, 2005