Geology 12 - Historical Geology
Course Syllabus	Course Schedule	Assignments	Department Home Page	Kusnick Home Page

Cambrian

Reading: Chapter 10

The main things we want out of this chapter are 1) the evidence for Cambrian environments and 2) the evidence severe weather leaves behind. Be sure to note the links to other Web Sites and be sure to visit them to answer the questions.

Background

Terms you should know:

Key Concepts and Questions:

1. Breakup of the Proterozoic supercontinent

What is the evidence that at least one supercontinent existed in the Proterozoic? (we'll do this in class)

To see reconstructions of the Proterozoic supercontinent:

• Go here, click on Precambrian, then Cambrian
• For an interactive look, go here, then click and drag the cursor across the image to run the animation.

 

What is the evidence that a supercontinent broke up at about 500- 600 mya?

 

 

2. Cambrian rocks

What is the significance of each of these features of Lower Cambrian sandstones?

• very well rounded
• almost pure quartz
• frosted (microscopic abrasions)
• large and small scale cross-beds

  What do we conclude about how these sandstones were deposited? What does it tell us about the tectonic setting of North America (and much of the world)?

 

How did deposition change toward the end of the Cambrian? What does this tell us about paleogeography and plate setting?

 

 

3. Episodic events

Find at least three indications of severe weather events left behind in Cambrian rocks. Why would we expect the sedimentary rocks of this large epeiric sea to be impacted primarily by large episodic storms rather than gradual deposition?

 

 

 

 

4. What was the paleoclimate of North America during the Cambrian?

What evidence exists to tell us about paleoclimate?

 

 

Assessment

1. Proterozoic supercontinents

You should be able to:

• describe the evidence that Proterozoic supercontinents existed, and broke up about 500-600 mya.

2. Cambrian sediments

You should be able to:

• describe the origin of the Lower Cambrian sandstones and the evidence for that origin
• describe the change in depositional environments into the Middle and Late Cambrian and the implications of that change.

3. Episodic events

You should be able to:

• recognize an episodic event (such as storm surge) from its effect on the sediment
• explain why Cambrian sediments were especially subject to large storm events

3. Paloeclimate

You should be able to:

• describe the paleoclimate of the Cambrian and the evidence for that climate