Geology 12 - Historical Geology
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Sedimentary Facies

Please print these handouts and bring to class:

Facies Activity

Transgression/Regression

Reading: Chapter 4 & 8

This is one of our most important topics of the semester. Plan to read this material now and review it again a few times in the second half of the semester. We will be doing quite a lot of work in class to help you learn this material.

Chapter 4: start at The Formation on p.75 through the end of Biostratigraphic Concepts on p. 82

Chapter 8: start at Terrigenous Versus Nonterrigenous Sediments on p. 159 through the end of Stratification on p. 163.

Background

Terms you should know:

Key Concepts and Questions:

1. How do we recognize ancient sedimentary environments (p. 159-163)?

View modern depostional environments here. For each environment, look at the picture of the modern environment AND the rocks that result from that environment.

What are the properties of rock that vary with environment?

 

 

 

Sedimentary structures are features formed during deposition that give clues to the environment. Find these four sedimentary structures from the reading, and describe how they form:

laminations

cross-stratification (cross-beds)

ripple marks

graded baedding

List one more sedimentary structures from the lecture and how they form:

 

 

 

Once we have reviewed the environments in class, fill out this chart with a brief description of the rocks formed in each environment:

river channel
floodplain
ocean beach
lagoon
alluvial fan
shallow marine
deep marine

2. How do we recognize how ancient environments changed over time?

What pattern in the rocks tells us transgression has occurred? Draw it.

 

 

 

What pattern in the rocks tells us regression has occurred? Draw it.

 

 

 

What events can cause global changes in sea level?

 

 

What events can cause local changes in sea level or shorelines?

 

 

3. How do we correlate rocks?

How do we correlate rocks using lithology? Does this correlation indicate that the rocks are the same age? Why or why not?

 

 

 

How do we correlate rocks using fossils? Does this correlation indicate that the rocks are the same age? Why or why not?

 

 

What other methods of correlation can we use? How does each one work?

 

 

 

 

Assessment

1. Sedimentary facies

You should be able to:

• identify potential depositional environments for a rock given its lithology, color, fossil content and sedimentary structures
• recognize where transgression or regression has occurred
• cite possible causes of shoreline changes for both global and local sea level changes

2. Correlation

You should be able to:

• correlate between stratigraphic columns using lithology, fossils, or magnetic characteristics
• describe the meaning of each kind of correlation: lithologic. biostratigraphic, magnetostratigraphic
• describe possible sources of error in each kind of correlation, and possible ways to control the error