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
Other sedimentary structures are made by organisms and these can also be used to tell us something about the depositional and environmental conditions of the area.
In the upper part of this outcrop, you can see layering in the rock in the form of ripples and crossbeds which would suggest a beach type of environment. In the bottom half of the photo, however, you see this jumbled up texture. This mottling is due to organisms burrowing through the sand. So what we are seeing here is a distinct boundary indicating a change of environmental conditions. (Eocene Torrey Sandstone, Solana Beach, southern California)
This is a Paleozoic trace fossil, a trackway of an ancient arthropod (probably a trilobite). These marks were made by the legs of the organism as it crawled through the sediment. Trace fossils can be used to interpret the depth, wave energy, ecology, and other factors in an environment at the time the sediments were deposited. (Upstate New York) This is an escape burrow (another type of trace fossil) which an organism (probably an arthropod) leaves behind as it tries to crawl up out of a layer of rapidly-deposited sand. A storm might have dumped a lot of sand into this environment and an organism tried to dig its way out of this layer. So this trace fossil tells us something about ancient behavior of an organism and it tells us something about the environment as well. (Eocene Torrey Sandstone, Solana Beach, southern California)
updated February 11, 2002
UCMP Home | What's new | About UCMP | History of Life | Collections | Subway
