1. Folding of Shale-Sandstone sequence, Kings Canyon, California FOLDS and thrust Which deformation and stresses cause theses structures ?

2. … Compression …Shortening

3. The fold is like a Thrust defined by its orientation Parts of a fold: –axial plane – limbs –“hinge” Hinge

4. Types of Folds Anticline = arch Syncline = trough Monocline = stair step Dome or Basin Chevron Fold, Laurel Mt., CA

5. Syncline syncline, Israel Youngest rocks in middle

6. Anticline Virgin anticline, southern Utah Oldest rocks in middle

7. Domes & Basins Think of an Egg Carton! Chernicoff and Whitney

8. Grenville Dome: Sinclair, WY Map from Topozone.com

9. Syncline- Anticline Pairs + Domes: Zagros Mts, Iran NASA “Earth as Art” web page

10. Monocline

11. Fold Classification

12. Fold in Glacier, Antarctica

13. Folds axis are perpendicular to the main direction of compression

14. Little Shuteye, Sierra Nevada, CA David Rogers Casey Moore, UCSC Domes are not produced by horizontal but vertical compression

15. Minor Folds and Foliation Are Clues to Much Larger Structures

16. Foliation Pressure –pressure flattens and/or aligns minerals in a rock –platy or sheet-like structure reflects the direction in which pressure was applied –Slate, schist, and gneiss foliated Microscope Image of Foliated Garnet Schist, VT 1 mm

17. Foliation In every case, the foliation is: In the direction of least resistance at right angles to the direction of greatest compression.

18. Fold And Foliation

19. Folds and Foliation

20. How Geologists Use These Clues Here's an outcrop that might be seen in the field.

21. Minor Folds and foliations can be used to determine the axe of the fold

22. Pay attention it migth look like folds K = Cretaceous J = Jurassic Tr = triassic At X, we have younger rocks surrounded by older rock

23. But it is produced by differential errosion on a thrust Dark green is older rock, thrust over the younger yellow rock The Klippe (K) W is a Fenster or Window

24. Folds and and Thrust are often associated The overturned fold in the upper diagram may break, yielding an overthrust fold or thrust fault

25. Folds and thrust have the same origin

26. Small thrust fault, Las Vegas, NV, Source: M. Miller, U. of Oregon Reverse Fault

27. Thrust Faults in Snow

28. fold-thrust complex developed in Upper Jurassic limestones in the Haut Giffre area of the Subalpine thrust belt (Morcles nappe in France) R.W.H. Butler Folds and thrust are both responsible for the orogens

29. Folded Appalachians Near Harrisburg, PA, Source: NASA

31. Folding in Malaspina Glacier, AK, 1969

32. Oil and Gas Concentrate in Domes Chernicoff and Whitney

33. Growth of Minerals

34. Bohlen et al., 1987 Folded Amphibolite in Marble, Warrensburg (K. Hollocher, NYSGA field photo) Small Scale Structures Mimic Large Scale Structures!!

35. Mulwaree fault zone, Australia, Tullis et al. Foliated Gneiss, Nunavut, S. Tella Photo. Foliated Slate, Shelburne, VT, UVM Foliation Macroscopic and Microscopic Feldspar (strong) Quartz (weak) Mulwaree fault zone, Australia

36. Pressure K. Hamblin A. Kronenberg Cararra Marble Deformation Experiments BrittleDuctile

37. Continental Extension Chernicoff and Whitney

38. Nevada Bureau of Mines and Geology Basin and Range

39. Extension – Crust Thins Ductile – Faulting Brittle

40. Shearing –lateral slip creates faults –common at transform boundaries

41. Faults –result from brittle deformation –rocks offset across fault –Sides referred to as “hanging wall” and “footwall” –3 types of fault Hanging Wall Footwall

42. Strike & Dip –Describe fault orientation –Direction of slip determines kind of fault: “dip-slip” or “strike-slip” Chernicoff and Whitney

43. Normal Fault, Lamb Canyon, CA Normal Fault

44. Strike-slip fault near Las Vegas, NV, Source: M. Miller, U. of Oregon Strike-Slip Fault

45. Strike-slip fault displacement in orchard

46. Joints Brittle “cracks” in rocks Form near surface Regular spatial distribution No offset

47. Calcite veins in joints of marble, Laurel Mt., CA Preferential weathering of joints in Sandstone;