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
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