Geology 12 - Historical Geology
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Middle Paleozoic

Reading: Chapter 12

Ch. 12: start at The Silurain and Early Devonian Continent (p. 269); skip the section on life (we'll use it later) on p. 258-269. Also reread the section in Ch 12 on the Western Cordillera (p. 292-293).

Background

Terms you should know:

Key Concepts and Questions:

1. Eastern subduction boundary (?) leading to collisions

What is the evidence of subduction during Silurian time?

It's pretty sparse. Read p. 271 and look carefully at Fig. 12.17 on p. 272. Look at the facies near the eastern margin of the continent.

Compare the plate tectonic diagrams on p. 294 (Fig. 12.45) and p. 320 (Fig. 13.280 for two competing hypotheses on the Middle Paleozoic eastern margin of North America. How are the models different?

 

 

 

What is the evidence of a Devonian collision? How do we know how old the collision was? What collided with North America?

 

 

On the facies map on p. 286 (Fig. 12.35), what type of tectonic basin is represented by:

• the Catskill Redbeds

 

• the Forest City Basin

 

 

2. Cratonic deposition

Look carefully at Figure 12.17. Are the edges of the Silurian rock shorelines, or are they just the edge of the eroded Silurian rock? What can you interpret about the paleogeography of North America during this time?

 

 

Reefs: How did the development of reef complexes:

• relate to the depostion of evaporites in the Michigan Basin?

 

• reflect paleoclimate in the Middle Paleozoic?

 

 

Assessment

1. Assembling Pangea

You should be able to:

• describe the evidence for successive collisions on the eastern margin of North America

2. Craton

You should be able to:

• apply what you know about sedimentary environments and tectonic stratigraphy to interpret the rocks of the Paleozoic craton