Interpreting Sea-Level Changes

Part 1: Beginning to Interpret Sea-level Changes

Answer the questions below. Your textbook will help greatly!

1 pt each

  

The diagram   above illustrates a transgression or a regression?

Regression

 

What is the   sequence of sedimentary rocks from the top of the vertical sequence at A to   the bottom? Give their names.

1. Sandstone

2. Shale

3. Limestone

1 pt each

  

The diagram   above illustrates a transgression or a regression?

Transgression

 

What is the   sequence of sedimentary rocks from the top of the vertical sequence at B to   the bottom? Give their names.

1. Limestone

2. Shale 

3. Sandstone 

 

What law   allows us to interpret sea level changes in this manner?

 

Describe this   law in your own words.

 

In what   situations would we be unable to use this law?

Part 2: Creating Lithofacies Maps

Read the directions on this page. Complete the maps and analysis questions that follow.

Lithofacies maps allow us to interpret the geology of the surface of a large region on earth quickly. The two diagrams below illustrate the creation of a lithofacies map. The left image shows us the data used to create the lines in the image on the right. Your task will be to complete several lithofacies maps using the data provided. You may print out the maps, complete them, and scan them to this Word document. You may also complete them digitally using InkScape, Adobe Illustrator, Microsoft Paint, or some other similar program. Only do this if you are comfortable using the software.

  

Lithofacies Map   Key

 

Abbreviation

Rock Name

Color

 

Cg

Conglomerate

Green

 

Ss

Sandstone

Yellow

 

Sh

Shale

Orange

 

ls

limestone

Blue

 

Example Data   Map created from the data

As you compare the two images, note that the lines do not cross and they do not touch the rock labels or dots. 

The two data maps shown below are of the same location but several thousand years separate the two. Complete the two lithofacies maps below now by drawing in lines to separate the rock types from each other and then adding color to help you see the changes more easily.

2 pts per map

 

      

m Z

 

      

m Z

1 pt each

  

Assuming the   top of these maps is north, where is the sea?

 

Has sea level   changed? Why or why not?

 

What event   occurred here, if any?

 

If you were   to drill a core sample at Z, what rock sequence would you expect to see   today?

1.

2.

3.

Complete the map below. – 2pts

      

m A

1 pt each

  

Assuming the   top of the diagram is north, where would you expect the sea to be? 

 

The land?

 

If you were   to drill a core at A and the sea was receding from a previously high level,   what is the vertical sequence you would expect to see here? Fill in the list   to the right with the names of the rocks you would expect to find with the   rock on the surface as 1.

1.

2.

3.

 

What is a   drop in sea level known as? Transgression or regression?

Part 3: Stratigraphic Correlation – 5 pts

The diagram above shows how to correlate strata. Use the diagram of the cores below to determine the stratigraphic relationship amongst them. Draw lines that indicate correlating rock layers.

  

Describe any   changes in the rock record that occur in the cores above.

 

What   stratigraphic sequence is shown in cores 1, 2, and 3? 

 

What does   this tell us about the geologic history of the region these cores were taken   from? (Hint: The type and order of these rock layers is significant!)