Cochise College Student Papers in Geology
Geology Home Page physical geology historical geology
Roger Weller, geology instructor regional geology planetary gems
wellerr@cochise.edu
Burgess Shale
by Victoria Hermosilla
Historical Geology
Spring 2008
Burgess Shale
One of the most important fossil finds in regards to life in the
Paleozoic is the Burgess Shale fossil find in Canada. No other find offers more
diversity of complete soft-body and plant fossils from the pre-Cambrian time or
the intricate detail of the fossils preserved. The site is extremely unique due
to the almost perfect preservation of soft body organisms, which hardly leave
any fossils. The Burgess Shale and its unique fossils offer a unique and
significant view into the past for geologists and paleontologists alike.
Located in beautiful British Colombia near a small town called
Field is the site of the Burgess Shale.
http://www.canada-for-you.com/imageC4U/BurgessShaleMeteorMapJohoNtl.Park_sh.gif
This exceptional site is at the Walcott Quarry “located in
Yoho National Park
in the Rocky Mountains” (MacRae) and is approximately 2500 feet in elevation
(Burgess Shale Foundation). It is approximately a 3 hour hike with stunning
scenic views “including Takakkaw Falls, Emerald Lake, numerous glaciers, and
high mountains” (Burgess Shale Foundation).
The Burgess Shale originally began forming about 530 million years
ago (Monroe-Wicander p232). Since most of the fossils found are marine fossils,
it can reasonably be assumed that the shale was formed in the ocean.
http://paleobiology.si.edu/burgess/cambrianWorld.html
Paleontologists believe that at the time of the formation of the Burgess Shale,
“the land was completely devoid of life (land plants and animals had not yet
evolved). Life on earth consisted only of marine plants and marine invertebrate
animals” (Burgess Shale Foundation). From the formation found in the Walcott
Quarry, paleontologists can also logically figure out that the Burgess Shale was
formed on an escarpment, now called the Cathedral Escarpment, which was a
carbonate reef in a warm, shallow sea (Burgess Shale Foundation). This was
during the Sauk flooding period on what was to become present day North America
(Monroe-Wicander p238).
At times, a piece of the reef would break loose causing a great underwater mudslide which would bury any organisms that got in the way. This is how the fossils got there in the first place. Over time, many layers built up creating the shale seen today.
Illustration by Victoria Hermosilla
The carcasses must have been protected from scavengers and decomposing bacteria
in an environment devoid of oxygen. It is thought that due to the turbulence of
the mudflows that overcame the animals, fine-grained clay particles were forced
into every crack and crevice of the animals (including their guts), separating
each delicate appendage also. This clay coffin protected the animals from
scavengers, and inhibited their decomposition. As a result, the complete forms
of many of the animals are preserved, which has made these fossils extremely
valuable to paleontologists.
Burgess Shale Foundation
Over time as the Earth’s plates shifted and the orogenic forces lifted the area,
the fossils found at the Walcott quarry remained untouched and in great
condition. Considering the forces involved and how much change has actually
occurred, it is remarkable that the fossils would remain in such good form.
Charles Walcott was a well known man in the geological world at the turn of the 20th century. He was a paleontologist who was the Director of the US Geological Survey while at the same time serving as the fourth secretary of the Smithsonian from 1907 to 1927 (The Beauty in Service). A simple hike in 1909 by Charles Walcott is what led to the discovery of the fossils in the Burgess Shale.
http://www.nceas.ucsb.edu/~alroy/lefa/Walcott.html
He found some fossils close to the trail he was on, and then excavated more
fossils at a location higher up which later became known as the Walcott quarry
(Burgess Shale Foundation). Walcott then spent the next several years
excavating thousands of fossils and sending them to the Smithsonian Institute in
Washington D.C. (Burgess Shale Foundation). Then Percy Raymond came along in
1930 and excavated first at Walcott’s Quarry, and then at a location about 60
feet higher. This new location is now called Raymond Quarry (Burgess Shale
Foundation).
The significance in the Burgess Shale find is not only the wealth of
a variety of specimens, but also the detail in which they were preserved. The
mudslides that caught the organisms captured every detail of many organisms,
from the skin patterns to delicate limbs. The fleshy parts that usually
decompose were preserved in the fine mud. The pressure from the amount of
overlying mud “also penetrated and filled all available spaces within the
animals, thus preserving the shapes and locations of all the soft parts” (The
Burgess Shale).
Fossil of Leanchoilia, Phylum Arthopoda
http://www.burgess-shale.bc.ca/images/leanchoilia.jpg
As can be seen in this picture, the detail of the fossil is pristine. This is
extremely valuable to paleontologists since this sort of event is so rare.
There are so many fossils at the Burgess Shale site that help fill in the gaps
from other, less complete fossils found in other locations. For example, this
trilobite is well preserved and shows a lot of detail.
Olenoides serratus.
This is the largest of several species of trilobites found in the Burgess Shale,
some of which have been preserved with soft appendages
http://www.geo.ucalgary.ca/~macrae/Burgess_Shale/
What is even more astounding is the variety of forms found in the shale that bear no resemblance at all to any life forms seen today (Monroe-Wicander p238).
Hallucigenia sparsa Wiwaxia Opabinia regalis
http://facstaff.gpc.edu/~pgore/geology/geo102/burgess/burgess.htm
The Burgess Shale site is a treasure trove of information and discovery. From its ideal location and preservation, to its discovery and excavation, it has helped shape the world of geology and paleontology. The uniqueness of the formation and preservation of the site is extraordinary while the detail and abundance of the fossils found is unmatched. This significance in the realm of science cannot be outdone. The Burgess Shale is a World Heritage Site that offers knowledge of this planet’s past, and will continue to open the eyes and minds of many people to come.
Works Cited
“Charles Doolittle Walcott (1850-1927)”. Lefalophodon: An Informal History of Evolutionary Biology Web Site. 26 April 2008
http://www.nceas.ucsb.edu/~alroy/lefa/Walcott.html
Gore,
Pamela J. W.
“Fossils of the Burgess Shale - Middle Cambrian.” 18 February 2004. Georgia
Perimeter College. 26 April 2008
http://facstaff.gpc.edu/~pgore/geology/geo102/burgess/burgess.htm
MacRae, Andrew. “Burgess Shale Fossils.” University of Calgary. 26 April 2008
http://www.geo.ucalgary.ca/~macrae/Burgess_Shale/
“The Beauty in Service to Science.” Smithsonian Institution Archives. 26
April 2008
http://siarchives.si.edu/techsvcs/walcott/main_article.htm
“The Burgess Shale.” The Department of Paleobiology. 2007. Smithsonian
National Museum of Natural History. 26 April 2008
http://paleobiology.si.edu/burgess/index.html
The Burgess Shale Geoscience Foundation. Home page. 26 April 2008
http://www.burgess-shale.bc.ca/index.php
“The Cambrian World.” The Department of Paleobiology. 2007.
Smithsonian National Museum of Natural History. 26 April 2008
http://paleobiology.si.edu/burgess/cambrianWorld.html
Wicander, Reed, Monroe, James S. Historical Geology. United States:
Thompson Brooks/Cole, 2007. 232, 238.
