GLG 435 SEDIMENTOLOGY
Instructor: Paul Knauth PSF 546 480 965-2867 Knauth@asu.edu
Office Hours: 2:00 - 3:00 WTh, other times by appointment, drop-ins welcome but
subject to wait time
Teaching Assistant: Kat McFadden PSF 574; Office Hrs: TF, 11:30-12:30; or make appointment
Kathleen McFadden <pitpatkitkat@hotmail.com>
Text: Principles of Sedimentology and Stratigraphy by Sam Boggs, Jr., 3nd Ed.
Grade breakdown (tentative):
First one-hour exam...............................................17% (Feb 25, 2003)
Second one-hour exam........................................ 19% (March 27, 2003)
Final exam ............................................................. 25% ( May 9, 2003)
Labs……….............................................................. 39%
Field Trip Labs:
March 8: Rim country; Depart 7:30 am; return 6:30 p.m.
April 25-27: Grand Canyon; Depart: 3:00 p.m. Friday Return : 6:00 p.m. Sunday
Regular Labs (Begin 1/28/03): About 6, several of which are done in the field (Papago Park, Tempe Butte, etc.)
1st Reading assignment:
For the first several weeks, we will be learning about material covered in the following pages. There will be some additional reading in the text associated with the labs. Start working on the assignment below NOW. This can’t be digested in one gulp, so chip away at it in concentrated reading sessions.
25-43; 46-47; 54-55; 88-130
SEDIMENTOLOGY STUDY SHEET
Exam #1 is scheduled for February 25.
The following questions are a study guide for the lecture and text material. The assigned reading so far is:
25-43; 46-56; 88-130; 274-284
Note also text material relevant to the labs (268-274; 59-87)
1. What is the difference between laminar and turbulent flow? Which type is most abundant in geological systems?
2. Explain with sketches the concept of a boundary layer.
3. How can you assess the Froude number by throwing rocks into a stream?
4. How are current ripples formed? Sketch the flow and consequent grain movement.
5. What types of flow patterns develop by flow separation around obstacles? Sketch the boundary layer in front of, and behind, obstacles of various shapes.
6. How does secondary flow give rise to sand ribbons?
7. Sketch the sequence of bedforms that develop with increasing flow strength. Which of these are common in nature? What type of bedding does each create?
8. Sketch a set of climbing ripples and explain what causes them.
9. Sketch the sequence of rippled beds in plan view that develop when the flow velocity increases. What is the effect of depth on this sequence?
10. How does grain size affect the sequence of bed forms that develop with increasing flow strength?
11. What is lenticular bedding? Flaser bedding? What does each tell you about flow conditions?
12. What are the flow mechanisms which generate alluvial fan deposits? What are the characteristics of the deposit created by each? Sketch the vertical succession of beds that might be created by an alluvial fan system. How might this succession vary?
13. Discuss grain size and sorting in an alluvial fan deposit.
14. What is the flow pattern of a river at a bend? Sketch.
15. Sketch the ideal vertical succession for a point bar deposit. In terms of the fluid flow over a point bar, why is this succession produced?
17. What are scroll bars and how do they form?
18. Explain what natural levees, crevasse-splays, and flood basins are. What type of deposit is created by each. What structures might you expect?
19. Be able to distinguish between the vertical stratigraphic sequences produced by meandering versus braided rivers (be sure you understand how the vertical sequence is created by lateral migration of the channel(s) over the floodplain).
Some questions based primarily on the reading assignments:
Pages 25-43:
1. Be sure you understand and can use Figs. 2.9-2.12.
2. Understand the HjulstrÖm diagram, Fig. 2.5. Why is such a high velocity sometimes required to move extremely small particles in the size range .001-.002 mm?
3. The Shields diagram gives the ultimate answer to the question: "What is the maximum size grain that can be moved by a given flow velocity?" This diagram, however, is difficult to use. What parameters would you need to know in order to answer the question?
4. Using terms of the Reynolds number, why might a lava flow be laminar rather than turbulent?
Pages 46-56:
1. Make sure you understand and can use Table 2.2, p. 47.
2. What is the fundamental difference between a liquified flow and a grain flow?
3. What can account for inverse grading in otherwise massive sandstone beds?
4. Make sure you understand and can recognize the different types of gravity flow deposits shown in Fig. 2.17.
5. Be able to sketch and label a Bouma sequence. Also, be able to explain why the sequence occurs in terms of the flow regime concept.
Pages 88-130:
1. Be able to use Fig. 4.10 to explain the possible role of depth on the types of ripples.
2. Study well all the figures of sedimentary structures in this section. For the photographs shown, be able to explain the origin of the structures if presented with a photo or sketch (For now, it is sufficient to recognize trace fossils as such. Don’t try to memorize trace fossil ichnofacies).
3. How do sandstone dikes form?
4. Be sure you can recognize the distinctive pattern of a stylolite (Fig. 4.48). You will see these in the field (and on the marble walls of bathroom stalls). What do they represent?
Pages 268-284:
1. Make sure you understand the depositional components of an alluvial fan system, including how they might vary vertically and laterally.
2. Study and understand thoroughly the diagrams in Figs. 9.9-9.16. Point bars and meandering rivers commonly yield vertical stratigraphic sequences that are distinctive and recognizable. It is important that all aspiring sedimentologists be thoroughly familiar with these sequences and their variations. It is especially important to be able to distinguish meandering river sequences from braided sequences.