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Geology of Mojave National Preserve: Evidence of Ancient Life

Tilted Paleozoic limestone layers
As you drive along the road from Baker toward the Kelso Dunes, you'll notice tilted beds of gray limestone. The limestone formed at a time (Paleozoic Era-about 570-240 million years ago) when the North American plate straddled the equator and tropical seas periodically covered the Mojave region. Countless shelled sea creatures lived and died in the shallow waters. Their calcium carbonate shells slowly accumulated on the sea bottom forming an oozing lime mud.
Orange tube shapes are the paths of burrowing animals preserved in the rock

Worms and other burrowing animals munched their way through the mud, eating the algae and other nutrient-rich food it contained. Records of their paths have been left behind as orange and dark gray tube-shaped burrows in the limestone. If you look carefully you'll also see tiny clam-like brachiopod shells and dark gray balls of algae.

Fossilized ball of algae, called an oncolith.
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