9. Announcements Midterm Monday
Announcements Midterm Monday! Bring calculator, protractor, ruler, stereonet and tracing paper Talk This Thurs. 4 pm, Rm. Haury Bldg. Rm 216, "The role of orogen-parallel extension during the India-Asia collision", write 1 paragraph summary (+1% extra credit)

10. Brittle fault rocks and kinematic indicators (D&R: 280-286; 297-300)
1. Descriptive terminology 2. Determining direction of slip 3. Determine sense-of-shear

11. Breccias: fault rocks composed of angular fragments of wall rock set in a finer-grained matrix of crushed wall rock; classified based on clast size
megabreccia! (well, almost)

12. breccia

13. gouge: very fine-grained; clayey

14. cataclasite: very fine-grained strongly indurated fault rock (white in photo)
concept of fault zone

15. cataclasite: commonly forms "ledges"

16. pseudotachylite: dark, very fine-grained and generally glassy fault rock; thought to represent rapidly chilled rock melt, with melting of rock due to shear heating during an earthquake event- WOW!
the glassy surface is the "generation" surface and the black veins are "injection veins"

17. Determining kinematics from fault fabrics 1st step: figure out direction of slip 2nd step: figure out sense-of-shear- this requires looking at fabrics that are oriented perpendicular to slip direction

18. slickensides: polished shiny fault surfaces due to abrasive action slickenlines/striations: scratches

19. Grooves

20. Larger Grooves

21. chatter marks: step-like features oriented perpendicular to striations
onto sense-of-shear...
chatter marks: step-like features oriented perpendicular to striations

22. What is it?
top-to-the right
Crystal fiber lineations: produced by preferred directional growth of minerals during faulting in direction of movement

25. Drag folds

26. conjugate Riedel shears
R: synthetic Riedel shear R': antithetic Riedel shear P: synthetic shear, subordinate to R and R' or absent

27. What is it? R' R' R R main fault left lateral
Where are R and R' shears? What is the sense-of-shear? Explain why R' shears are associated with veins

28. photo courtesy of Brent Morris

29. A summary What is it?
breccia
cataclasite
Riedel shears
gash fractures: form perpendicular to s3
normal fault

31. Important terminology/concepts
Breccias
megabreccia
breccia
gouge
cataclasite
fault zone
pseudotachylite
slickensides
slickenlines/striations
grooves
chatter marks
crystal fiber lineations
drag folds
Riedel shears
gash fractures