Home | Session 3 | Sedimentary Rock Pg 1, 2, 3, 4, 5, 6, 7, 8, 9
What's in a Sedimentary Rock?
Presented
by Carol Tang
California Academy of Sciences
This is a Jurassic shell bed made up of broken scallops (Camptonectes) all deposited parallel to the sea floor. A shell bed like this is usually interpreted as a storm deposit where lots of organisms were killed and their shells deposited very quickly. Strong storms are more likely to occur in shallower waters. (Jurassic Sundance Formation, central Wyoming)
In the last slide, we used the orientation of the shells to tell us something about the environment. In this slide, we can use the condition of the shells and the size of the shells to do the same thing. Here we have a mix of big and small as well as some complete and broken shells. This suggests that this fossil assemblage has not undergone a lot of sorting or transport yet since those processes would result in a more uniform size (smaller) and more broken fossils.
updated February 11, 2002
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