0457-3; Denali-1; Jurassic

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Wesley Gilmore
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1 STATION ; Denali-1; Jurassic Directions: Pick one rock. Describe the style of folding. Do a quick sketch and draw the axes of folds on your sketch. Use the ribbon and ruler to measure elongation due to folding. Remember shortening = negative elongation. Are the folds coaxial or non-coaxial? If coaxial, draw σ1 on your sketch. Make a guess at the rock type and explain your guess.

2 STATION 2 Kodiak, Montana Directions: Pick one rock. Do a sketch and denote at least two generations of structures. Describe each. How do you know which came first? What are the particular features of the rock which give you that idea? Make a guess at the rock type and explain your guess.

3 STATION 3 ` Eclogite, UCSC, Cone Peak, 523, thin section Directions: These rocks contain minerals of equant, elongate, and platy shapes. Fill in the spaces in the table below with either none or a few words describing the minerals you can see in each rock. If you don t know the names, give color, luster, etc: Eclogite Equant Minerals Elongate Minerals Platy Minerals UCSC Cone Peak 523 Look at thin section in the microscope. Move it around on the stage. Spin the stage. Flip the cross polarizer in and out. That s the tiny toggle switch high on the left side of the microscope body. With the polarizer in, you can see individual crystals of quartz (black, white, gray) which look just all clear without the polarizer. Describe at least 4 minerals different minerals, stating their color, relief (how much does it appear to stand out against other minerals?) and typical shape.

4 STATION 4 Poleta BAF Mylonite, Laramide, Antigorite, thin section WB4 Directions: Pick a rock. Does it contain equant, elongate, or platy minerals, or are they even visible? Describe whatever you can see, try to guess at what you can t see. Can you see planar fabrics (surfaces) or linear fabrics within the rocks? Describe them. Was this ductile rock deformed coaxially or non-coaxially? Look at thin section WB4 in the microscope. Move it around on the stage. Spin the stage. Flip the cross polarizer in and out. That s the tiny toggle switch high on the left side of the microscope body. With the polarizer in, you can see individual crystals of quartz (black, white, gray) which look just all clear without the polarizer. The black minerals are clays and the yellowish (with polarizer) are calcite. Which minerals are where with respect to the shear fabric in the rock? The diagram below shows a simple fabric called S-C fabric. Label where the different minerals occur or write a caption. C S S C

5 STATION 5 Directions: Ano Nuevo ; Chert. Pick one and do a really nice sketch. This station is all about the sketch. Include any and all structural features in the rock. Explain how faults and folds are related. Describe any observed contrasts in stiffness within the rock. Describe any alteration found along the fault zone. What feature do these rocks share that makes bedding so clear?

6 STATION 6 Directions: Kronkite, CL-12, Ambassador What structure do all these rocks share? How are they different? What was the source of the stress which caused this structure in each rock? (your best guess, and justify it.) Hint: CL-12 has extensional veins, Kronkite has shear veins.

7 STATION 7 Directions: Trilobites; Conglomerate. Pick one and sketch. If trilobites: What was the direction of maximum elongation relative to north? Was deformation coaxial or non-coaxial? Give a detailed answer discussing any complications that you observe. If conglomerate: if marked pebble was originally spherical, what is apparent elongation as seen on that cut surface? Sketch what you measured. Discuss the contrast in deformation style between the two big dark red pebbles (marked)

8 STATION 8 RM20B, Jenner, Parkfield, thin section Directions: These rocks contain minerals of equant, elongate, and platy shapes. Fill in the spaces in the table below with either none or a few words describing the minerals you can see in each rock. If you don t know the names, give color, luster, etc. In the overall rock fabric column, say which mineral shape dominates the overall shape and cleavage of the rock. RM20B Equant Minerals Elongate Minerals Platy Minerals Overall rock fabric Jenner Parkfield Thin section Look at thin section in the microscope. Move it around on the stage. Spin the stage. Flip the cross polarizer in and out. That s the tiny toggle switch high on the left side of the microscope body. With the polarizer in, you can see individual crystals of quartz (black, white, gray) which look just all clear without the polarizer. How does grain shape control/effect fabric? Find quartz grains which cross cut fabric. Do a sketch of what you see in the microscope in the circle.

Chapter 8 Lecture. Earth: An Introduction to Physical Geology. Twelfth Edition. Metamorphism. Rocks. Tarbuck and Lutgens Pearson Education, Inc.

Chapter 8 Lecture. Earth: An Introduction to Physical Geology. Twelfth Edition. Metamorphism. Rocks. Tarbuck and Lutgens Pearson Education, Inc. Chapter 8 Lecture Earth: An Introduction to Physical Geology Twelfth Edition Metamorphism and dmetamorphic Rocks Tarbuck and Lutgens Chapter 8 Metamorphic Rocks What Is Metamorphism? Metamorphism means