SO461 Geological Oceanography

Fall 2015 Test 1

 

Definitions

4 @ 7 points

28

 

Diagrams

6 @ 12 points

72

 

Total

 

100

 

 

Authorized reference:

  1. You may use one 3”x 5” card, personally hand written on both sides, during the exam.  You will turn it in with the exam.
  2. Calculators will not be allowed.  For the calculations, you may set it up and leave the answer in terms of a sum, product, or quotient, or you can make reason simplifications to get a rough idea of the answer.

 

Diagrams: These should clearly indicate understanding of the procedures and concepts involved, and should be well thought out with appropriate terms and details to support your answer.  You must answer 6 of the 7 questions.

 

 

Budget your time.   Do not leave anything blank, and note that I am looking for an understanding of the important concepts and appropriate use of  terminology.

 

All work on this exam is individual.  You may not any materials (books, notes, computers) other than your personal 3”x5” note cared, and you may not use IM, texting, talking, or any other means to communicate with other individuals.  If you are caught with an electronic device that is not turned off and inaccessible you will get a 0 on the exam.

 

 



Definitions: Answer 4 of the 5, for 7 points each.  Indicate why each is important

 

·       Hutton:  (half skipped)

·       K/Ar or Rb/Sr:   (half skipped)

·       Quartz:

·       Regression/Transgression:

·       Unconformity


 

You must answer 6 of the 7 remaining questions on the next 5 pages, for 12 points each.  Each has a figure or table.

Figure 1.  Geoid anomalies from the TOPEX/Poseidon altimeter, Cycle 364: (A) Orbit 8, (B) Orbit 48, and (c) Orbit 51.

 

How is the geoid anomaly computed, and what does the altimeter actually measure that enables it compute the geoid?

 

 

How can the altimeter measure something else that would be of interest to oceanographers rather than geologists?

  

 

The three profiles have different vertical and horizontal scales.  What plate tectonic feature do you think is causing each anomaly and why do you think this?

 

A:

 

 

B:

 

 

C:

 



Figure 2.  P-wave velocities from three sites in Leg 165 of the IODP.

 

 

What is the P-wave velocity?

 

 

Which site do you think has the thinnest soft sediment cover before you go into well lithified rock?  Why do you say this?

 

 

 

Can you predict anything about sediment density or porosity at these sites?  Why or why not?

 

 



Figure 3.  Drilling results from site 1128 on ODP Leg 182.

 

Table 1.  Shipboard age determinations for site 1128 on ODP Leg 182.

 

Holes A and B were drilled from the same ship position, and C and D had the ship move 20 m for each.  All were drilled in about 3800 m of water.  All recovered fossils were Cenozoic.

 

What happens to the sedimentation rate in Hole B at about 60 mbsf?

 

How do the apparent sedimentation rates compare among the three holes?  Do you think that is reasonable over a distance of 40 m?

 

 

How are the ages determined?

 



Figure 4.  Profiles drawn on two different continental margins.  Note sea level shown on each, and that the scales on each differ.

 

How should the locations for these profiles have been drawn?  Why?

 

 

How do these two margins differ?

 

 

 

 

Can you say anything about the age of the sea floor on the right side of each profile?  Why or why not?

 

 


 

 

Figure 4.  Motions along a plate boundary.

 

 

Could this plate boundary be a subduction zone?    How would you have to interpret the vectors for this to be true, or why cannot it be a subduction zone?

 

 

 

 

Can you locate the Euler pole for this motion from the information on the map?

 

 

 

 


 

 

 

What kind of plate boundary is depicted in the diagram on the left?

 

  

Would the type of plate boundary change if Plate 1 and Plate 2 switched positions?

 

  

The vectors depict the same location; the maps are shifted slightly to keep the vectors and labels on the map.  Can these two motion vectors depict the same plate boundary?  Why or why not?

 

 

  

Can you say anything about the Euler pole with just a single point’s velocity?
 

 


Table 2.   Sediment locations.

 

Location

Expected Sediment Type

Thickness

Equator, center of major ocean basin

 

 

 

 

Mid ocean ridge, eastern Pacific Ocean

 

 

 

 

Center of gyre, northern Pacific Ocean

 

 

 

 

Congo Delta, equatorial Africa