Stop 1 RT 374 Roadcut
At our first stop we will examine a number of features.
First, in the photo below note the dark band of rock cutting across the gray, bedded rock.
What would this dark band be called? (Review pages 86 through 92, "Intrusive Rock Formations" in the Chernicoff & Whitney text.) What would its probable composition be?
There's an odd aspect to this rock that you should note. In the photo below, you can see that it has speckles!
The speckles are actually made up of calcite. How, or why, would this type of rock develope blebs of calcite? (see p.84 in text, and remember the concept of Magmatic Contamination from lecture).
Lastly, why is this black rock even here? What might it tell us about the history of the area? (see p.87 in text).
Now what about the bedded rock? It contains abundant fossils (see photo below). What type of rock might it be? (review pages 182 - 194 in text).
Finally, at the west end of the road cut the bedded rock changes in texture and color. What we have here is called a "contact" between two different rock units. What causes this? Review pages 194- 200 on ""Reading" Sedimentary Rocks", especially page 200 on "Shifting
Sedimentary Environments".