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STRATIGRAPHY
Lesson 4 - Page 3

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The California coast has been subject to movement because of transform motion of two major plates. Mudflats that were once home to millions of organisms slowly were uplifted exposing their remains along the cliffs. Layers of fossils represent millions of years of accumulation. You can find mollusk including bivalves and gastropods, bones from marine mammals, sand dollars, and even crab claws.

Many times the shells are in distinct layers, with few still having two shells. Paleontologists have deduced that this represents storm layers. A storm would come in with violent waves and rip up the mollusk community. After the storm the shells would create a "burial" layer. In between the storm layers, you can find bivalves  whose shells are still intact, so they lived to a ripe old age.


Marine mammals


Mollusk fossils in mudstone

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