#lagerstatten

This month has been dedicated to the Cambrian Period. Something most people are not aware of is that Paleozoic and Mesozoic periods are broken down into epochs and stages...just like the Cenozoic.

Just for fun I wanted to use this column of the Cambrian Period to show where all the major deposits and animals we've talked about (and a few we haven't) occurred.

Like our favorite trilobites!

Trilobites appeared in the fossil record at about 521 Ma, right at the end of Stage 2 of the Terreneuvian Epoch. Not long after that, the Chengjiang and Sirius Passet lagerstatten were deposited. This was towards the end of Stage 3 of Series 2. This is when the animal Haikouella lived.

Next is Emu Bay Shale. We haven't talked about that one yet. As you can imagine, Emu Bay is in Australia on Kangaroo Island.

It is one of two sites containing Redlichiidan trilobites.

The Burgess Shale was deposited at the beginning of the Drumian Age during the Mialingian Epoch. This is when Hallucigenia and Marella lived.

This is followed by the Wheeler Shale, Marjum and Weeks Formation sequence in the Guzhangian Age.

The final lagerstatten is the Orsten Fauna of Sweden. The fossils are just a little bit younger than the Utah ones and much smaller. This site preserved larval stages and the first fossil tardigrades.

By the end of the Cambrian there was a major faunal turnover into the Ordovician Period. Many brachiopods and conodonts died but the group that was hit the hardest was the trilobites. Those that lived on the outer edges of the shelfs and slope environments were hardly affected but those that lived in the shallow seas on the shelf were wiped out.

The Cambrian Period was important and I hope you enjoyed learning about it this month. Next month we will switch from geochronology to paleontology with comparative anatomy! There will be a video on the basics posted to youtube on October 19th but if you want to see it sooner then join my new Patreon! The video will be posted two weeks earlier.

There will also be interviews with my fellow paleontologists as well as lesson videos and access to the Minerals Rocks and Fossil Talks discord server. Thanks for all the support and fossilize you later!

No, I am not going to be talking about the novel. I am going to be talking about how awesome a year it was for paleontology starting with a man named Higgins. He was exploring Greenland for a Geological Survey of Greenland.

Little did he know he was about to make the discovery of his life: the Sirius Passet Lagerstatte.

This Cambrian lagerstatte is found in the Buen Formation. It is 15 million years older than the Burgess Shale of Canada. About 10,000 specimens have been collected including an elongated trilobite called Kleptothule.

That same year clear on the other side of the world in Chengjiang County, Yunnan Province China, another lagerstatte was discovered. This one is known as the Maotianshan Shales.

The shales were first recognized for their exquisite preservation with the discovery (in 1984, of course) of Misszhouia, a soft-bodied cousin of the trilobite.

I was looking at Lagerstätten one day and realized that a vast number of them are found in Cambrian age rocks. It got me thinking: why are so many found in Cambrian rocks? Let's take a look and see what these have in common.

Emu Bay Shale, Australia

Lower Cambrian, depositional environment: restricted basins on inner shelf.

Kinzers Formation, Pennsylvannia

Middle Cambrian, depositional environment: deep water, outer shelf

Burgess Shale, British Columbia

Middle Cambrian, depositional environment: below storm wave base

Spence Shale, Utah and Idaho

Middle Cambrian, depositional environment: continental shelf (both inner and outer).

Marjum Formation, Utah

Middle Cambrian, depositional environment: deep water.

Wheeler Shale, Utah

Middle Cambrian, depositional environment: below shelf where turbidites are deposited.

Weeks Formation, Utah

Middle Cambrian, depositional environment: gentle slope below the carbonate platform.

Maotianshan Shale, China

Early-Middle Cambrian, depositional environment: below turbidity currents where turbidites form.

Sirius Passet Formation, Greenland

Middle Cambrian, depositional environment: slope below carbonate platform

Sinsk Formation, Russia

Early Cambrian, slope below carbonate platform

So, as we can see, most of these were formed in the Middle Cambrian below a carbonate platform or shelf also known as a reef. It would seem that if you want to be exceptionally preserved, live along the continental shelf slope and get buried in mudslides, or storm deposits.

New caption video with a clip from Episode 2: Terra Incognita Part 2

Thank you so much to everyone who has already listened to our first episode, and been liking and sharing our posts, it means a lot to us to see you enjoying the show!

In episode two, Brie begins to discover the secrets of Tartarus, some of which she may not be ready for…

Tartarus Episode 2 available online June 14th

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In Tartarus, an anxious astrobiologist, the terse manager of a secret Antarctic facility, and an A.I, keep humanity safe from the monsters they imprison. Episode 1: Terra Incognita Part 1 Available Now

Spotify: https://open.spotify.com/show/2leH0IYgTcLLQcWmXuXvlb

Exceptional Preservation A fossil is the remains or traces of an organism preserved from the past and they can be exceptionally preserved, recording extremely fine detail or some remains of soft tissue. There are certain conditions that lend themselves to exceptional preservation, including rapid burial, low energy, lack of oxygen and acidity. If an organism is buried rapidly in a protective material such as a soft clay it will be protected from both weathering processes and scavengers. This is not enough to guarantee exceptional preservation, and so it may be combined with other factors; low energy environments for example are the best chance of fossilisation and both a lack of oxygen or high acidity reduce decay, among other factors.

There are two methods of exceptional preservation that are particularly striking, these are preservation by tar and amber. Tar pits such as those at Rancho La Brea, California are formed when hydrocarbons migrate up through water farming a pool on the surface. Water then accumulates on top of this pool attracting animals to bathe and drink. When an animal enters the pit they become stuck, their struggling then attracts others, both attempting to prey on and aid the stuck animal. Eventually those trapped die due to a combination of exhaustion, drowning, stress and dehydration.

Amber is hardened tree resin. Tree resin form inside trees, when a tree is injured amber flows out of cracks in the bark to seal the break. Insects become trapped in the amber, which then hardens preserving the insect inside the amber. ~SA

Picture: http://bit.ly/1JklbFl cast of a tar preserved Wooly Rhino by Paul Hudson and http://bit.ly/1DjBSZb Acropyga glaesaria preserved in amber by http://bit.ly/1HzDowq

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