Fossil enthusiasts pick through the offerings at the Burgess Shale quarry near Field, B.C. Photograph by : Warren Tasker/Canwest News Service
Posted on 02/22/2008 2:27:37 PM PST by Renfield
It's been called the world's single greatest assemblage of primeval fossils - an accidental Canadian treasure that scientists literally stumbled upon 100 years ago in B.C.'s Rocky Mountains.
The Burgess Shale fossil site in present-day Yoho National Park is a one-of-a-kind, 530-million-year-old time capsule containing the stunningly well-preserved remains of an entire undersea ecosystem from a crucial phase in the history of life - a lost world filled with dozens of bizarre creatures destined to become evolution's losers, but also with a primitive ancestor of the human race itself.
Now, a team of British and Canadian scientists has solved the long-standing mystery of how the UNESCO World Heritage Site near the B.C.-Alberta border was formed at the dawn of the so-called Cambrian "explosion" of life - a time when the future Canadian land mass was drifting in tropical climes close to the Earth's equator.
By looking over hundreds of micro-thin slices of rock taken from the famous shales, the researchers have reconstructed the series of catastrophic underwater landslides of "mud-rich slurry" that killed tens of thousands of marine animals representing hundreds of species, then sealed them instantly - and enduringly - in a deep-sea tomb.
The mass death was "not a nice way to go, perhaps, but a swift one - and one that guaranteed immortality (of a sort) for these strange creatures," said University of Leicester geochemist Sarah Gabbott, lead author of a study published in the U.K.-based Journal of the Geological Society.
Desmond Collins, a Royal Ontario Museum paleontologist and Burgess Shale expert who co-authored the study, described how the steep wall of rock now popular with Rocky Mountain tourists was once a "submarine cliff, with animals living on the sea floor at its foot. Currents rising up the side of this cliff would have brought a great concentration of nutrients, attracting lots of animals to the area."
But over time, massive clumps of muddy silt built up along the cliff would suddenly give way and entomb the creatures below.
"They would have to buried quickly and deeply enough that scavengers couldn't dig them up," said Collins, adding that the oxygen-free depths of the Cambrian oceans ensured the creatures' remains decayed at extremely slow rates.
"It is most unusual," he said, "to find the soft tissues of these animals preserved the way they are."
Among the imprints of animal remains excavated from the Burgess Shale is one called pikaia, an eel-like creature that has been classified as the earliest known, identifiable ancestor of modern vertebrates - including humans.
Fossil enthusiasts pick through the offerings at the Burgess Shale quarry near Field, B.C. Photograph by : Warren Tasker/Canwest News Service
Paleontology ping....
“Evolution’s Losers?” I think they survived and called “Democrats” now.
This may elicit some interesting responses!
“a primitive ancestor of the human race itself.”
The Piltdown crab. The Java mullosk.
It is a beautiful site, with plates of trilobytes everywhere.
What is fascinating, not discussed, is that the “seabed”
is at circa 10,000 feet.
Stephen Jay Gould’s “Wonderful Life” is a great book about the Burgess Shale and the creatures represented in it.
For a revolutionary view of life and the Burgess Shale read the book Wonderful Life, The BurGess shale and the Nature of History by Stephen J Gould.
The book describes the work of the discoverer and his proteges who built on his discoveries and expanded the field of biology ina quantum leap.
Creos should stay away because if the read it they are in danger of learning something
Cambrian oceans- salt water or fresh water?
I’ve been tempted to pick that up a few times, but put it down because I was slightly put off by Bryson’s “I’m a Stranger Here Myself”. Thanks for the recommendation. I’ll look at it again.
Another great “Science For non-Scientists” book is “The Whole Shebang” by Tomothy Ferris. It’s physics and cosmology for the general reader.
Salt.
The summit of Mt. Everest is marine limestone and is former seabed between India and Asia.
If you perceive it's not discussed, it's because it's so common for marine sediment to get tectonically pushed up into mountains around the world, it's unremarkable to geologists.
Good point. In the Burgess shale, the climber
suddenly sees that every shale stone upon which he is sliding contains several trilobyte fossils.
Not as preserved as the sands of Northern Africa,
but there in their splendid “immortality” nonetheless.
It is a sudden reminder that this Riemann surface has
time-traveled in space and time.
What can you see in the rocks and minerals at the top of Everest?
Huh. So I guess Burgess Shale isn’t a man’s name....
Good question. Only an abstract, but:
Abstract Newly discovered peloidal limestone from the summit of Mount Qomolangma (Mount Everest) contains skeletal fragments of trilobites, ostracods and crinoids. They are small pebble-sized debris interbedded in micritic bedded limestone of the Qomolangma Formation, and are interpreted to have been derived from a bank margin and redeposited in peri-platform environments.
"Fine-grained limestone from the summit of Gyachung Kang,
above the Qomolangma Detachment, containing fossil fragments. Field of view 2 mm."
"From its summit to the top of the Yellow Band, about 8,600 m above sea level, the top of Mount Everest
consists of the Qomolangma Fomation, which has also been designated as either the Everest Formation
or Jolmo Lungama Formation. It consists of grayish to dark gray or white, parallel laminated and bedded limestone
interlayered with subordinate beds of recrystallized dolomite with argillaceous laminae and siltstone.
Gansser[40] reported finding visible fragments of crinoids in these limestones. Petrographic analysis of samples of this
Ordovician limestone from near the summit revealed them to be composed of carbonate pellets and finely fragmented
remains of trilobites, crinoids, and ostracods[/b]. Other samples were so badly sheared and recrystallized
that their original consitutents could not be determined.
The Qomolangma Formation is broken up by several high-angle faults that terminate at the low angle thrust fault,
the Qomolangma Detachment. This detachment separates it from the underlying Yellow Band.
The lower five metres of the Qomolangma Formation overlying this detachment are very highly deformed.[41][42]"
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Thanks Renfield. |
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