Home | Session 4 | Shallow Marine Pg 1, 2, 3, 4, 5, 6, 7, 8
Shallow Marine Environments and Paleoenvironments: Reefs, Beaches and Basins
Presented
by Carol Tang
California Academy of Sciences
Wave refraction
Due to wave refraction, waves generally come at an angle to shore and thus, transport of sand can occur down the coastline (called longshore transport). See:
http://www.geol.ucsb.edu/~arthur/UCSB_Beaches/beachclifferosion.html
When human structures interfere with the waves, you can have erosion on one side and deposition on the other side.
See: http://www-class.unl.edu/geol109/Images/groins.jpg
In that example, erosion is occuring to the left of the groin (the structure jutting out perpendicular to shore) and deposition to the right. So longshore drift is moving sand from right to left.
Paleoenvironmental reconstructions
Important to reconstruct for:
- Climate change studies
- Earthquake studies
- Evolutionary studies
- Oil sources and reservoirs
- Composition of grains (see sand activity from Session 3) e.g., kinds of grains, size of grains, angularity
- Sedimentary structures (see Session 3 lecture), e.g., mudcracks, ripples, dunes
- Fossil content, e.g., abundance, communities
Organisms are sensitive to depth and distance from shore:
- Light levels
- Water pressure
- Wave energy
- Nutrients
- Sediment input
updated April 1, 2002
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