Invertebrate Zoology – ZOOL 3104. Burgess Shale How are fossils made? Animal is buried (dead or...
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Transcript of Invertebrate Zoology – ZOOL 3104. Burgess Shale How are fossils made? Animal is buried (dead or...
How are fossils made?
• Animal is buried (dead or alive)– Mud, silt, volcanic ash, or sand
• Fossils could also be frozen in ice, mummified in hot or cold deserts, or preserved in tar
• Usually, all of a living thing’s soft parts decay, leaving only the hard parts
How are fossils made II
• Replacement: the minerals replace, molecule by molecule, the hard parts or the remains
• Permineralization: minerals fill in the spaces of the hard parts of the remains
Burgess Shale
• Made famous to the general public by Stephen Jay Gould. 1989. Wonderful Life: The Burgess Shale and the Nature of History
Burgess Shale
• Shale is a sedimentary rock formed by the deposition of successive layers of clay.
• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.
Burgess Shale
• Shale is a sedimentary rock formed by the deposition of successive layers of clay.
• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.
• Cambrian rock formation over 500 million years.
Burgess Shale
• Shale is a sedimentary rock formed by the deposition of successive layers of clay.
• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.
• Cambrian rock formation over 500 million years.
• So, what is so special about it?
A unique place
• Exceptional preservation of soft bodied marine invertebrates.
• Over 65,000 fossil specimens of 120 species from the Burgess Shale are housed at the Smithsonian.
How preservation works?
• Good preservation indicates deposition in anoxic conditions
• Many delicate details of soft part anatomy are preserved. (Legs and gills of trilobites, etc.)
How preservation works?
• Good preservation indicates deposition in anoxic conditions
• Many delicate details of soft part anatomy are preserved. (Legs and gills of trilobites, etc.)
• Swept off an adjacent, well-oxygenated carbonate platform by turbidity currents, and killed and protected from decay in anoxic water
The initial discovery
• Charles D. Walcott (1909)
• Secretary of the Smithsonian Institution
(1850-1927)
The Animals
• Mud dwellers, filter feeders
• Strollers, walkers and crawlers
• Swimmers and floaters