Undergraduates uncover the past at Aust

A group of students from the University of Bristol excavating the ancient cliffs at Aust have uncovered a rare array of fossils as part of a special summer undergraduate project.

Their findings were published in Science Direct earlier this year, providing an intricate account of the newly revived ecosystem, which is located close to the eastern end of the Severn Bridge connecting England and Wales.

Aust Cliff is a 20m-high, reddish-grey cliff under the English side of the Old Severn Bridge, just outside the small village of Aust. “It has major historical importance,” says student Sam Cross, lead author of the paper. He has just finished his first year studying Palaeontology and Evolution at the University of Bristol.

“It is important to European geology and is a recognised site of special scientific interest. It was one of the first locations in the world where the geological boundary between the Triassic and Jurassic periods was documented,” Sam continues. “Therefore it remains one of the best locations to observe this transition”.

A view of the Old Severn Bridge from Aust Cliff, near the excavation site

In the paper, the authors discuss the discoveries they made at Aust, including different types of coprolites. “Coprolites are fossil poops,” says fellow UoB student Nikola Ivanovski. “You can work out who made the poop by their size, and then explore the fossilized contents.”

“We also found Parascylloides turnerae, a rare species of shark only known from two other sites, one in the UK and another in Germany,” Sam says. This rare find made the painstaking excavations in Aust worth it for the team.

“From start to publication it’s taken just over a year,” Sam says. “It involved multiple different steps. First, the bone bed samples had to be dissolved in acid producing a sediment which contained the tiny fossils. Second, we had to manually pick through the sediment to get those fossils, and third the fossils had to be identified. Once that was done we could begin to analyse our findings and begin to look at how Aust compared to other locations’ bone bed and how the ecology of the Aust community would have functioned.”

The distinctive red rocks at Aust Cliff contain secrets about the Triassic and Jurassic periods

Over the course of the project, the students have identified around 5,000 specimens, with help from Adam Parker, the technician in the University of Bristol’s School of Earth Sciences. He said: “These are classic preparation methods. You take great blocks of the bone bed and reduce it by a process of mild acid treatment, washing and concentrating to make the job of picking out the fossils quicker.”

In total the students identified six species of sharks and four species of bony fishes at Aust Cliff, as well as other unidentified scales and assorted bones.

Close ups of fossils found in rocks at Aust Cliff. Image: Michael Day via Flickr.

The site at Aust has long been known as a site for fossil hunters looking for finds. “As long as the tide is out, Aust Cliff is accessible to visitors,” Sam advises. “Though it might not be best to acid-treat the bone bed at home!

“Look for pieces of greyish rock with black lumps in them, as those lumps might be bones. Often if you look carefully you can see small teeth, the kind described in the paper, on the surface.”

For more information about the project as a whole, visit www.bristol.ac.uk/news/2018/july/aust-cliff-fossils-.html