GEOL 360, Structual Geology

1. GEOL 360, Structual Geology www.geology.cwu.edu/blue.hmtl enter g360 in left navbar search and hit enter, this is the class home page • Class information & syllabus • Laboratory & class materials • Stereonet exercises • Problem sets • Exam review

2. Meeting: G360 meets MWF 11:00-11:50, Lind 103 Laboratory, Wednesday at 2:00 pm, Lind 103 Text: Structural Geology of Rocks and Regions, Davis and Reynolds, 1996 Supplemental Text: Geology in the Field, Compton, 1985. Instructor: Dr. Charles Rubin, charlier@geology.cwu.edu. Office: Hebeler 109 Telephone: 963-2827 Office hours: My office door is usually open or by appointment Teaching Assistant: Josh Dailey Office: Bouillon, Rm 120 Telephone: 963-2707

4. Why is it important? • Fundamental discipline in Earth Sciences- “the study of the architecture of the Earth’s crust” • Geometry is key to many ES applications (oil, mining, earthquake hazards, slope stability); • Our goals: • to learn how to make structural observations & present them to others; • to interpret the processes that led to the “final • product”- the geologic observations.

5. Student learning objectives: Develop an understanding of (1) the scientific method, (2) rock deformation, rock failure, strain and stress, (3) types of faults and folds, kinematic analysis, stereographic analysis of faults and folds, (4) construction and interpretation of geologic cross-sections. Problem sets: There will weekly assignments during the quarter. Late assignments will be deducted 10% per day that they are late. Laboratory assignments: Many of the laboratory assignments for this course require a lot of thinking as well as some repetitive, time-consuming work. Please do not wait unit the day before the assignments are due to begin working on them. Problem sets: There will weekly assignments during the quarter. Exams will be graded by Charlie Rubin. We do not accept a late assignment after we have returned the graded exercise to the rest of the class.

6. Some tips for a successful quarter: • Do not miss a class, not one. Reading your text is not a substitute for attending lecture. • Read your text assignments before class askquestions and participate in class. • Take good, complete notes. The more you write, the better. If you do not understand a concept or example, ASK. If I go too quickly, ask me to repeat the information. • If you do not understand a concept that I discuss in class, ask questions during class or come and see me. The only way I can help you understand the material is if you ASK for help!

7. Some tips for a successful quarter: It is to your advantage to study and work with other students in this course. Discuss your laboratory exercises and data, its analysis and interpretations with others members of the class; this is a constructive and realistic way of solving geologic problems. However, your final product should be your own individual and creative work. If you have any questions about the acceptability of collaboration, ask Charlie Rubin before you complete the assignment, not after. Remember, few aspects of geology are completely cut and dry, your laboratory exercises are not exception to this. Don't forget scientific writing style, logic, organization, data quality, and presentation are all part of the final product.

8. - ME - • I’m an professor of Geological Sciences and teach a mix of undergraduate and graduate classes, which I enjoy doing • I teach GEOL 360. I also teach other courses such as G101 (intro geology), G170 (EQ’s and volcanoes), G415/515 (earthquake geology), G410 (physics of avalanches), and G210 (field geology), and seminars on the active tectonics of mountain belts.

9. GEOL 360 addresses the architecture of the Earth - the physical components or structures that make up the Earth’s crust, and that form in response to applied forces and stresses.

10. What is structural geology – study of deformed rocks, sediments, and landforms • necessary to define geometries of land forms and rocks in 3D • Observations • direct: mapping, drill holes, laboratory, experimental • indirect: seismic, gravity, magnetics, etc. • What do we do? • measure or infer translation, rotation and strain (deformation history): KINEMATICS • related to engineering mechanics and material science, but, we almost always only have the end-product • engineers want to know effect of stress on an object • geologists try to infer stress from deformed object; • much more difficult: MECHANICS & DYNAMICS

11. We have these goals: • Critical thinking & the scientific method • Analytical methods to decipher earth processes • Scientific principles that govern Solid-Earth processes • Observational techniques & reasoning processes GOALS FOR Geol 360

12. Comfort with new language • lots of new terminology throughout the course. • use the book’s glossary for quickie refresher GOALS FOR Geol 360

13. Present lecture material that accounts for • different learn styles: • seeing/visual • reading • hearing • personal discovery GOALS FOR Geol 360

14. Deformation - used in several ways:1) Structural changes in location, orientation, shape, and volume of a body of rock.2) Physical and chemical processes that cause the changes.3) Geologic structures that form to accommodate the changes.Any body of sediment/rock, regardless of strength will deform if conditions are right. Space Shuttle view of the Greater Himalayas

16. Deformation of the Earth’s Crust Deformation results from stresses that exceed a rocks strength.When peak strength is reached, failure is either brittle (fracture) or ductile (flow), depending on how the physical environment has affected rock strength (e.g., temperature, strain rate, etc.).Stresses are applied to rocks in countless ways: burial, cooling/heating, intrusion, plate motion, impacts from space.The structural geologist is faced with a finished product and has the inverse task of learning how it came to be - effectively the opposite task that faces an architect.What is the structure? What were the starting materials? What’s the geometry? How did it change shape? Source of stresses? Sequence of deformation?

17. Deformed fossils (trilobites), showing strain

18. Deformation is the result of plate tectonics and is observable. • Plate motions are responsible for many of the stresses that cause deformation of rock. • Distortions of the Earth’s crust are most prominent at plate margins; the location of much of the Earth’s high mountains.

19. engineering: observe what happens apply stress structural geology: ? infer what happened and original shape observe deformed object to describe deformation, one needs a reference frame, typically the reference frame is the “undeformed state” modified from Allmendinger: http://www.geo.cornell.edu/geology/classes/RWA/GS_326/GEOL326.html#aa40

25. Fundamental Structures • Contacts • The most basic structures, they separate one rock unit from another: • Depositional • Unconformities • Faults • Intrusive • Shear zones

26. Fundamental Structures • Primary Structures: These are primary sedimentary structures. They are useful as strain markers (giving us an initial state) and as stratigraphic facing indicators. • Do not confuse primary sedimentary structures with secondary structures, which are the result of deformation. up Bedding Laminations Graded Bedding

27. Cross-Beds (asymmetric) Oscillation Ripples (symmetric) up up

29. Mud Cracks Rain Drops / Footprints up up

32. Load Casts Tool Marks up up

33. up up Root Casts / Worm Burrows Stromatolites

34. Primary vs. secondary structures. Primary: depositional contacts, cross-bedding, ripple marks, Ropy textures in lavas, mud-cracks;

35. Geologic structure at different scales: regional (Landsat TM) global (Topex/Poseidon) from: http://topex.ucsd.edu/marine_grav/explore_grav.html

36. Macroscopic (map scale) Keystone thrust (dark over light) Calico folds both from: Robert Varga, http://www.wooster.edu/geology/GEO313/Images/

37. Mesoscopic (outcrop) all from: J. Waldron, http://www.stmarys.ca/academic/science/geology/structural/

38. Mesoscopic (hand sample) sigmoidal structures (shear zones) from: Keck geology slide set, Paul Karabinos site: http://www.science.ubc.ca/~eoswr/slidesets/keck/ folds in gypsum from: J. Waldron, http://www.stmarys.ca/academic/science/geology/structural/folds2.html

39. Microscopic: s-c fabric from: J. Waldron, http://www.stmarys.ca/academic/science/geology/structural/ Dynamic recrystallization (formation of s-c fabric) from Allmendinger: http://www.geo.cornell.edu/geology/classes/RWA/GS_326/GEOL326.html#aa40

40. Microscopic and mesoscopic: vein image from: J. Waldron, http://www.stmarys.ca/academic/science/geology/structural/ animation from Allmendinger: http://www.geo.cornell.edu/geology/classes/RWA/GS_326/GEOL326.html#aa40

41. Scale of analysis.

42. “Tools” for interpretation Original horizontality (Nicholas Steno) Layers that are tilted were deposited horizontally Fundamental concept that gave birth to structural geology from Stephen J. Reynolds, (http://www-glg.la.asu.edu/~sreynolds/geologic_scenery/geologic_scenery_images.html

43. Importance of strike and dip to describe geometry 2 perpendicular lines that together define the plane N tilted layer b strike horizontal plane = strike angle inclined plane strike measured relative to north in horizontal plane dip strike strike in and out of plane of page a = dip angle vertical layers dip measured relative to horizontal along line of strike dip dip

44. Superposition of strata: in a sequence of undeformed rocks…… oldest rocks are on the bottom with progressively younger rocks found at higher stratigraphic positions Stratigraphic “facing” is an important tool for structural geology are the layers right side up or upside down? upside down implies deformation

45. time 1 time 2 time 3 time 4 from Stephen J. Reynolds, (http://www-glg.la.asu.edu/~sreynolds/geologic_scenery/geologic_scenery_images.html

46. Cross-cutting relationships where geologic features intersect, the feature doing the “cutting” is the youngest feature unconformity cuts down into strata below Grand Canyon Great Unconformity