Burgess Shale
Burgess Shale | |
---|---|
Ma | |
Type | Geological formation |
Unit of | Stephen Formation |
Thickness | 161 meters (528 ft)[1] |
Lithology | |
Primary | Shale |
Location | |
Coordinates | 51°26′N 116°28′W / 51.433°N 116.467°W |
Region | Yoho National Park and Kootenay National Park |
Country | Canada |
Type section | |
Named for | Burgess Pass |
Named by | Charles Doolittle Walcott, 1911 |
Map highlighting Yoho National Park in red |
The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada.[2][3] It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old (middle Cambrian),[4] it is one of the earliest fossil beds containing soft-part imprints.
The rock unit is a black shale and crops out at a number of localities near the town of Field in Yoho National Park and the Kicking Horse Pass. Another outcrop is in Kootenay National Park 42 km to the south.
History and significance
Part of a series on |
The Burgess Shale |
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The Burgess Shale was discovered by
Excavations were resumed at the
With
Stephen Jay Gould's book Wonderful Life, published in 1989, brought the Burgess Shale fossils to the public's attention. Gould suggests that the extraordinary diversity of the fossils indicates that life forms at the time were much more disparate in body form than those that survive today, and that many of the unique lineages were evolutionary experiments that became extinct. Gould's interpretation of the diversity of Cambrian fauna relied heavily on Simon Conway Morris's reinterpretation of Charles Walcott's original publications. However, Conway Morris strongly disagreed with Gould's conclusions, arguing that almost all the Cambrian fauna could be classified into modern day phyla.[7]
The Burgess Shale has attracted the interest of
After the Burgess Shale site was registered as a World Heritage Site in 1980, it was included in the Canadian Rocky Mountain Parks WHS designation in 1984.
In 2012, the discovery was announced of another Burgess Shale outcrop in Kootenay National Park to the south. In just 15 days of field collecting in 2013, 50 animal species were unearthed at the new site.[9]
IUGS geological heritage site
In respect of the site being 'characterized by exceptional soft-tissue preservation, [and containing] the most complete fossil record of Cambrian (Wuliuan) marine ecosystems', the International Union of Geological Sciences (IUGS) included the 'Burgess Shale Cambrian Paleontological Record' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an 'IUGS Geological Heritage Site' as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'[10]
Geological setting
The fossil-bearing deposits of the Burgess Shale correlate to the
It was originally thought that the Burgess Shale was deposited in
Stratigraphy
The Burgess Shale Formation comprises 10 members, the most famous being the Walcott Quarry Shale Member comprising the greater phyllopod bed.[11]
Taphonomy and diagenesis
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There are many other comparable Cambrian
Biota
The biota of the Burgess Shale appears to be typical of middle Cambrian deposits.[6] Although the hard-part bearing organisms make up as little as 14% of the community,[6] these same organisms are found in similar proportions in other Cambrian localities. This means that there is no reason to assume that the organisms without hard parts are exceptional in any way; many appear in other lagerstätten of different age and locations.[6]
The biota consists of a range of organisms. Free-swimming (nectonic) organisms are relatively rare, with the majority of organisms being bottom dwelling (benthic) — either moving about (vagrant) or permanently attached to the sea floor (sessile).[6] About two-thirds of the Burgess Shale organisms lived by feeding on the organic content in the muddy sea floor, while almost a third filtered out fine particles from the water column. Under 10% of organisms were predators or scavengers, although since these organisms were larger, the biomass was split equally among each of the filter feeding, deposit feeding, predatory and scavenging organisms.[6]
Many Burgess Shale organisms represent stem group members of the modern animal phyla, though crown group representatives of certain phyla are also present.[20]
A comprehensive list can be found at Paleobiota of the Burgess Shale.
Working with the Burgess Shale
The fossils of the Burgess Shale are preserved as black carbon films on black shales, and so are difficult to photograph; however, various photographic techniques can improve the quality of the images that can be acquired.[21] Other techniques include backscatter SEM, elemental mapping and camera lucida drawing.
Once images have been acquired, the effects of decay and taphonomy must be accounted for before a correct anatomical reconstruction can be made. A consideration of the combination of characters allows researchers to establish the taxonomic affinity.
See also
- Body plan
- Fezouata Formation, a fossil site in Morocco that helped bridge the gap of the Cambrian-Ordovician transition
- Castle Bank
- History of invertebrate paleozoology
- Invertebrate paleontology
- List of fossil sites (with link directory)
- Maotianshan Shales, which is often compared to Burgess Shale
- Paleobiota of the Burgess Shale
- Wheeler Shale, also compared to Burgess Shale
References
- ^ Lexicon of Canadian Geological Units. "Burgess Shale". Archived from the original on 11 January 2013. Retrieved 6 February 2009.
- PMID 21680421.
- )
- S2CID 29130876.
- ^ "Charles Walcott". Royal Ontario Museum. Archived from the original on 6 June 2013. Retrieved 29 August 2013.
- ^ OCLC 231793738
- ISBN 978-0-19-286202-0.
- ISBN 0-8050-7512-7
- ^ "New fossil bed found by scientists hailed as 'motherlode'". Canada. 11 February 2014. Archived from the original on 2 August 2023. Retrieved 2 August 2023.
- ^ "The First 100 IUGS Geological Heritage Sites" (PDF). IUGS International Commission on Geoheritage. IUGS. Archived (PDF) from the original on 27 October 2022. Retrieved 13 November 2022.
- ^ S2CID 128685811.
- .
- .
- S2CID 133486523.
- .
- PMID 9712577.
- S2CID 53646959.
- .
- .
- S2CID 205244325.
- ^ Bengtson, Stefan (2000). "Teasing Fossils out of Shales with Cameras and Computers" (PDF). Palaeontologia Electronica. 3 (1). Archived (PDF) from the original on 9 October 2022. Retrieved 3 December 2010.
Further reading
- Gould, Stephen Jay & Conway Morris, Simon. Debating the significance of the Burgess Shale: Simon Conway Morris & Stephen Jay Gould. "Showdown on the Burgess Shale". Natural History Magazine. 107 (10): 48–55. Archived from the original on 10 December 2010. Retrieved 17 August 2008.
- Conway Morris, Simon. The Crucible of Creation: The Burgess Shale and the Rise of Animals, Oxford University Press, Oxford, 1998 (paperback 1999) ISBN 0-19-286202-2(pbk)
- ISBN 0-00-655138-6
- Gould, Stephen Jay. ISBN 0-09-927345-4
- ISBN 1-56098-364-7
External links
- "Burgess Shale". Virtual Museum of Canada. 2011.
- Melvyn Bragg (host) (17 February 2005). "The Cambrian Explosion". In Our Time. BBC Radio 4 broadcast. (includes links to resource pages)
- Caron, Jean-Bernard; Gaines, Robert R.; Aria, Cédric; Mángano, M. Gabriela; Streng, Michael (February 2014). "A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies". PMID 24513643.