GEOL333 (Fall 2007) Structural Geology and Orogenesis

TuTh 11:00 – 12:15. Labs Tu 1:00 - 3:50. Mount Holyoke College

Michelle J. Markley, Associate Professor

office: 326 and 329 Clapp Hall ; office phone: 538-2814; email: mmarkley

Objectives

This course covers the basic techniques of field geology, structural analysis, and multidisciplinary approaches to mountain building (orogenesis). Lectures concentrate on field techniques, stress, strain, faulting, folding, fabric, rock strength, the relation between rock deformation and metamorphism, and deformation mechanisms. Of eight labs, five are field trips that involve collection of original data. Seven short problem sets emphasize quantitative skills. During the final weeks of the semester, students research the Alpine Fault of New Zealand. A final paper and two oral presentations emphasize fluency in the published literature of structural geology. Class participation constitutes 10% of the final grade.

Text

G. H. Davis and S. J. Reynolds, 1996, Structural Geology of Rocks and Regions, second edition (Wiley) is available from the Odyssey bookstore.

Problem sets

The purpose of problem sets is to hone your quantitative skills. I will pass out homework assignments on the days specified in the syllabus. The completed assignment will be due in class one week after you receive it. Each homework assignment is worth 2 points--the first for its timely completion and the second for the correct answer. I encourage you to work in groups on these problem sets. Problem sets constitute 10% of the final grade.

Labs

The purpose of labs is to develop your scientific argumentation skills and encourage you to create visual representations of your data and ideas in order to strengthen and clarify your arguments. Labs include two components: (1) making and documenting original observations, and (2) interpreting these observations in the context of class lecture material. Although I expect each of you to make original observations and interpretations, I encourage you to work together to develop strategies and ideas.

Lab write-ups are due to me a week after they are introduced to you, and I will return them one week later. Write-ups are late if I receive them after I have begun grading. Late write-ups garner no credit, but I will make comments on them as I do on graded ones. An enclosed set of "guidelines" summarizes my expectations. The syllabus contains a sheet called “Lab Write-ups” that will serve as the format for grades on labs. Labs constitute 40% of the final grade.

Oral presentations

Each student will make two oral presentations to the class. The purpose of these presentations is to explain specific scientific studies to your peers, ultimately creating a broad understanding (of a regional literature) that each student uses to guide thinking about her final paper. During each presentation, you will present material from an article on the geology of the Alpine Fault in New Zealand. Please practice your presentations at the Speaking Center. The syllabus contains a sheet called “Class Presentations” that will serve as the format for grades on oral presentations. Each oral presentation constitutes 10% of the final grade.

Final paper

A short (3 page) paper is due at the end of the semester. This paper is the only final assignment in the class, so use it as an opportunity to review and clarify material from the lectures and labs, or as an opportunity to extend your new knowledge into other disciplines. The final paper constitutes 20% of your final grade. This syllabus contains detailed descriptions of possible paper topics and format. I will run lab-time peer review sessions of the first draft of this paper. You must bring two copies of the complete first draft of your paper to the peer review session and turn in the second draft on the date specified in the syllabus.

Books on reserve at the library

G. H. Davis and S. J. Reynolds, 1996, Structural Geology of Rocks and Regions, 2nd edition (Wiley). This is your text. (QE601.D3 1996 Folio)

S. Marshak and G. Mitra, 1988, Basic Methods in Structural Geology (Prentice Hall). This is a standard lab manual for structural geology that has two parts: (1) "Elementary Techniques," with great how-to chapters on stereonets, attitude calculations from field data, and contour map construction; and (2) "Special Topics," with a wide range of mostly excellent chapters on topics such as rock deformation experiments, folds, cross-sections, and strain analysis. (QE601.M365 1988)

E. M. Moores and R. J. Twiss, 1995, Tectonics (W. H. Freeman). This is a good introduction to plate tectonics. (QE601.M65 1995 Folio)

C. W. Passchier and R. J. Trouw, 2005, Microtectonics, 2nd edition (Springer). This is a beautiful book intended for students at an advanced level. It has great photomicrographs (photos of thin sections of deformed rocks) and contains unusually well written chapters on a range of topics including flow and deformation, deformation mechanisms, small-scale structures, and how-to advice on orienting and cutting samples for structural analysis. ISBN 978-3540640035

R. J. Twiss and E. M. Moores, 2006, Structural Geology, 2nd edition (W. H. Freeman). This is a solid intro level text for structural geology that goes into more detail on most topics than your text does. ISBN 978-0716749516

CLASS SCHEDULE

If it's a Chapter in bold, read it in Davis and Reynolds or fall behind!

I. Introduction (Chapter 1; Part III sections A-D & H)

Thursday 9/6: Location and Orientation

PROBLEM SET #1: Strike and Dip

Tuesday 9/11 Using a Stereonet

LAB #1: Journal of Structural Geology

Thursday 9/13: More Stereonet

PROBLEM SET #2: Stereonet Practice

II. Brittle structures (Chapters 3, 5, and 6)

Tuesday 9/18 Stress & Fractures

LAB #2: Primary Structures (*field trip*) at Skinner Park

Thursday 9/20: Mohr Circles and Joints

PROBLEM SET #3: Mohr Circle problem

Tuesday 9/25: Mohr Circles and Joints

LAB #3: Fractures (*field trip*) at Skinner Park

Thursday 9/27: Fault Rocks

Tuesday 10/2: Faults

LAB #4: Clay Experiments

III. Ductile Structures (Chapters 7 and 8)

Thursday 10/4: Strain and Folding

PROBLEM SET #4: Beta Diagrams

CLASS CANCELLED 10/9 FOR MID-SEMESTER BREAK

Thursday 10/11: Foliation and Lineation

PROBLEM SET #5: Rotation on a Stereonet (Part III section I)

Tuesday 10/16: Foliation and Lineation

LAB #5: Foliation and Lineation, part 1 (*field trip*) of Moretown Formation

Thursday 10/18: Multiple Deformation Events

Tuesday 10/23: Multiple Deformation Events

LAB #6: Foliation and Lineation, part 2 (*field trip*) of Moretown Formation

IV. Kinematic Analysis and Strain (Chapters 2 and 9)

Thursday 10/25: Strain Analysis

PROBLEM SET #6: Pure Shear vs. Simple Shear

Tuesday 10/30: Introduction to the Alpine Fault

LAB #7: Journal of Structural Geology again

Thursday 11/1: Strain Analysis

PROBLEM SET #7: Strain Rates

Tuesday 11/6: Kinematic Indicators

LAB #8: Kinematic Indicators (*field trip*) at Pelham Dome

Thursday 11/8: Transpression and Transtension

V. Orogenesis and Conferences (Chapters 4 and 10)

Tuesday 11/13: Diffusion Creep

LAB TIME: Preparation for Oral Presentations

Thursday 11/15: Dislocation Creep

Tuesday 11/20: Preparation for Oral Presentations

LAB TIME: Preparation for Oral Presentations

CLASS CANCELLED 11/22 FOR THANKSGIVING

Tuesday 11/27: First Oral Presentations

LAB TIME: First Oral Presentations

Thursday 11/29: Rock Strength

Tuesday 12/4: Second Oral Presentations

LAB TIME: Second Oral Presentations

Thursday 12/6: Strength of the Lithosphere

Tuesday 12/11: lecture cancelled

LAB TIME: Peer Review of Final Papers

Thursday 12/20: Final draft of final paper due

Lab Write-up Guidelines

• Do not exceed the 1 page limit (shorter than 1 page is great!). One page means one 8.5 x 11 page with 1 inch margins, 1.5-spaced text, using a 12 point font such as Times.

• If you are writing about the results of field research, carefully describe the rock types (lithologies) you examined.

• Use tables to present your raw data on the orientations of various structures. Label each table and its column headings carefully (for example, Table 1: measurements of the orientation of primary and secondary features, including column headings like strike and dip of bedding, and trend and plunge of amphibole lineation).

• Use figures to clarify your arguments and present visually your results. Refer to each figure in the text of your one-page write-up, and label and title each figure.

For example:

Figure 1 shows that foliation is subhorizontal at the western end of the roadcut, although the orientation of schist foliation varies locally. Pegmatite veins consistently crosscut this schist foliation (Figure 2).

These statements are appropriate if the label to Figure 1 reads Figure 1: Equal angle stereographic projection of poles to schist foliation surfaces, western side of the roadcut, and the label to Figure 2 reads Figure 2: sketch of intrusive contact between schist and pegmatite, with 1 meter bar for scale.

• Write clearly and use scientific language (try reading your text if you lack vocabulary). Use the active voice whenever possible.

For example: During pure shear, a line with an initial orientation of 45° to the positive x axis experiences elongation and clockwise rotation.

• Elaborate on your observations and results. Spend the bare minimum of time on descriptions of how you made these observations.

For example: In general, bedding strikes east-west and dips ca. 30° to the north. Cylindrical open folds locally reorient bedding. b diagrams (Figure 1) show that fold axes trend north-south and plunge shallowly to the north.

• Remember that you are identifying plausible explanations for patterns in the data you collected. Think creatively, and justify your arguments and conclusions carefully.

For example: Joints tend to strike east-west, and this single orientation for the many joint surfaces is most consistent with predictions from the tensile fracture criterion (critical sn is constant). Joint geometry therefore suggests that this joint system developed in tension. This hypothesis, however, does not explain the few joints I observed that strike north-south. Joints in these orientations may result from...

• Discuss your results positively and consider the broad implications of your research rather than berating yourself or speculating about research you did not conduct.

For example: During the strike-slip experiment, fracturing occurred first along the edge of the block near my thumb imprint. This observation suggests that brittle structures such as fractures may nucleate at perturbations or inhomogeneities in materials.

Guidelines for Final Paper

You MUST bring two copies of your first draft of your final paper to lab on

Tuesday December 11 in order to review it with your peers.

The final draft of your final paper is due under my office door on Thursday December 20.

Attached MUST be the two copies of peer reviewed first drafts

Paper format

Typed and three pages long. Three pages means three 8.5 x 11 pages with 1 inch margins, 1.5-spaced text, using a 12 point font such as Times. The format and organization of your paper are up to you to decide, but you should include subheadings and references (consult any published article in the Journal of Structural Geology for format).

Topics

Please choose one of the following topics:

• Identify an unresolved question about the Alpine Fault that is geological, geophysical, or tectonic. Convince your reader that this question is both unresolved and interesting. Propose a research project that addresses this problem.

• Identify and discuss a conflict between the observations and/or interpretations in some of the articles. What is the nature of this conflict (i.e. does it relate to conflicting observations or interpretations)? Do you foresee any resolution to the conflict?

• Identify and discuss a common observation in some of the articles. Discuss the consequences of this observation for either structural or regional geologists.

Citations

Use five or more references (i.e. five articles from the list of literature on the Alpine Fault). You may use your two articles, although this is not required. In other words, you will probably reference and discuss your two articles and at least three other presentations. You may also read and reference some of the articles that no one presented.