GEL 109 Midterm W07 Study Guide and HW #5 Name:

For Home work: Answer 20 points worth of questions of your choice. 1. Are the following flow types typically laminar or turbulent and why? (3 points) a) water b) air c) ice 2. Where in a water flow is there usually a zone of laminar flow even if the bulk of the water is turbulent? Why is it laminar? (2 points) 3. What is the minimum flow speed necessary to transport 0.8 mm diameter coarse sand if it is already in motion? Use the Hjulstrom diagram in the text book. (1 point) 4. Would a meter-deep flow moving at 20 cm/sec transport cobble-sized clasts? What is the minimum flow speed necessary to transport 100 mm diameter cobbles if they are already in motion? (3 points) 5. Describe the Bernouli Effect and how it lifts grains off a bed at the base of a water flow. Your description can be either in words or an annotated sketch. (3 points)

GEL 109 Midterm W07 Study Guide and HW #5 Name:

6. In the following sketch of a subaqueous dune, sketch and label the features listed below. (6 points) This question will be on the test.

a) The separation and attachment points of the laminar/viscous sublayer b) The areas where deposition occurs c) The areas where erosion occurs d) The internal cross stratification within the dune. Include both the cross beds and the erosion surfaces separating sets of cross stratification. Make sure the geometry of the internal cross stratification corresponds to the other areas labeled.

7. List one thing that each of the following characteristics could tell you if they were present in a sandstone. (1 point each) a) grains are well sorted b) grains are poorly sorted c) grains are coarse sand d) grains are silt sized e) grains are well rounded f) grains are angular g) grains are predominantly clay minerals

GEL 109 Midterm W07 Study Guide and HW #5 Name:

8. Is the following picture more likely to show ripple x-lamination or dune x-stratification? Why? (2 points; the hand lens is 2 cm across)

9. a) Could photo A (next page) be a picture of ripple cross lamination? Why or why not? Be very specific. (2 points) b) Could photo B be a picture of ripple cross lamination? Why or why not? Be very specific. (2 points) c) Could photo C be a picture of ripple cross lamination? Why or why not? Be very specific. (2 points) d) Draw arrows next to or on photos A and C to show the direction of water flow. (2 points)

GEL 109 Midterm W07 Study Guide and HW #5 Name:

GEL 109 Midterm W07 Study Guide and HW #5 Name:

10. What direction(s) did the water flow during deposition of the outlined sediments in the following photograph? (2 points)

11. For the following stratigraphic column, describe how the velocity of the flow changed through time from 0 to 80 cm. Include descriptions of at least 2 types of features that allow you to make this interpretation, e.g. grain size changes, stratification styles, a model for how the sediment was deposited, etc. (4 points)

GEL 109 Midterm W07 Study Guide and HW #5 Name:

12. Which part of the deposit in the stratigraphic column above was deposited quickly and which part was deposited slowly, in relative terms? (2 points) 13. a) Write in the name of the appropriate sedimentary structure for each area of the diagram. Also write in the area with no sediment transport. (5 points)

a

Antidunes

Silt very f fine med coarse very cSand

20

60

100

b) Draw and label a line on the diagram above that shows how flow speed varied from the base to the top of the stratigraphic column in question 11. Note that dune cross stratification takes some time to develop, so dune cross stratification might not be present in the column even if the change in flow speed based on the diagram above suggests that it should. (3 points) 14. Describe in words the steps that lead to the deposition of a turbidite. (5 points)

GEL 109 Midterm W07 Study Guide and HW #5 Name:

15. How does rock thickness compare to the time represented by the rock, i.e. does thickness=time or not? Why? (4 points) 16. The following diagram shows the topography along which a river flows after it leaves the mountains. Part of the river is a braided river and part is a meandering river. (3 points; 1 point each)

a

Ocean

Mountains

High Slope

Low SlopeIntermediateSlope

AB

100’s km

a) Which segment of the river is most likely to be braided? A or B b) Which segment is most likely to be meandering? A or B c) Which segment of the river will be transporting the coarsest sediment? A or B 17. The following stratigraphic column represents deposits from a meandering river environment Label the deposits or features created by each of the following: (7 points)

a) base of a channel b) deposits in the deepest part of the channel c) deposits comprising the point bar d) flood plain deposits e) large flood deposit

Beside one of the SAND units, put an “F” for rocks deposited from the fastest flow and an “S” for rocks deposited from a slower flow. Put a “VS” next to rocks in the strat column that were deposited from the slowest flow. (The “VS” does not have to be in a sand deposit, but the “F” and “S” should be within the same group of sands.)

GEL 109 Midterm W07 Study Guide and HW #5 Name:

b) Draw a simple sketch that illustrates the processes that deposited the sediment in the environments going from 20 cm to 120 cm in the stratigraphic column above. Show the spatial relationship among the environments, in other words where they were located relative to each other. Make sure that the processes that you described in part a are labeled in your sketch, including the erosional surface. (Remember that Walther’s Law says that environments that grade into each other vertically in a stratigraphic section occur next to each other.) (6 points) Carbonate Questions – coming soon End-of-oil Questions – coming soon