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
Flat, layered bedding is the "default" pattern of sedimentary deposition. These layers as seen here can be used to tell us about the depositional environment. In this case, the alternating colors suggests changes in the depositional conditions. [Triassic formation, Northern Arizona]
These layers can also be seen in different scales. In this case, this flat bedding is much finer than that seen in the last slide. These thin layers are undisturbed suggesting that this was a quiet water environment where there weren't a lot of storms or currents to mix up the sediments (Monterey Formation, central California) When flat layers are disrupted and cut, one can also infer depositional events. Here you can see a small channel that has been cut through the parallel layers. What this shows is that the layers were deposited and then the channel was cut through the layers. (Triassic sandstone, northern Arizona) Here is another example of non-parallel beds which indicate environmental conditions. These are called flame structures and these form when thin beds of soft sediment are put under pressure. The soft sediment can become deformed and "squirt" up through the overlying layers.
updated February 11, 2002
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