Burgess Shale

The Burgess Shale is a special place where very old fossils can be found in the Canadian Rockies of British Columbia, Canada. These fossils are important because they show the soft parts of animals that usually do not fossilize. This helps scientists learn about life from a very long time ago.

The Burgess Shale is about million years old and dates back to the middle Cambrian period. It is one of the earliest places where fossils of soft-bodied animals have been discovered.

The rocks that make up the Burgess Shale are black shale and can be seen near the town of Field in Yoho National Park and also at the Kicking Horse Pass. There is another place where these rocks appear in Kootenay National Park, about 42 kilometers to the south.

History and significance

Main article: History of the Burgess Shale

The Burgess Shale was found by a scientist named Charles Walcott in 1909 in Canada. He started digging there and collected many fossils, which were special because they showed soft parts of animals that usually don't fossilize. At first, these fossils were not well understood, but later scientists realized they showed many different and strange creatures that lived a very long time ago.

More scientists came to study the fossils and found even more types of animals. Books and studies helped people learn about these ancient animals and what Earth was like back then. The Burgess Shale is very important for scientists who want to learn about Earth's past and even its far future climate. In 2012, another fossil site was found nearby, adding even more amazing discoveries to our knowledge of ancient life.

Geology

Main article: Stephen Formation

The Burgess Shale is a collection of fossils found in dark mudstones that are about 508 million years old. These rocks were formed at the bottom of a tall cliff, away from the waves that stirred up the water during storms. Scientists think that part of a nearby reef broke off and slid down, creating this special spot where fossils formed.

It was once believed that these fossils formed in places without oxygen, which helped protect them. But now we know that oxygen was present. Even with oxygen, the fossils were amazingly well preserved, including soft parts of the creatures. There were fewer animals that dug in the mud, which also helped keep the fossils intact.

The Burgess Shale is sometimes considered its own rock layer, separate from the Stephen Formation.

Taphonomy and diagenesis

The fossils in the Burgess Shale were quickly covered by sediment from water currents before they could decay. These currents might have moved the organisms a long distance before they were buried. The fossils are preserved as very thin carbon films, thinner than a thousandth of a millimetre.

There are many other places from the same time period with well-preserved fossils. This is because during this time, there was less digging and moving of sediment by living things, which made it easier to keep the soft parts of organisms intact.

Biota

The Burgess Shale has many different kinds of ancient sea creatures. Most of these creatures lived on the ocean floor, either moving around or staying in one place. Many of them ate bits of organic material from the muddy sea floor, while some filtered tiny particles from the water. Only a few were hunters or scavengers.

These creatures include early members of animal groups we know today, as well as some that are ancestors of modern animals.

Working with the Burgess Shale

The fossils in the Burgess Shale are preserved as dark films on rock, which makes them hard to photograph. Scientists use special photography methods to get better pictures. They also use tools like cameras and drawings to study the fossils.

After taking pictures, scientists need to think about how the fossils changed over time before they can understand what the ancient animals looked like. By looking at different features, they can figure out how these fossils are related to each other.