Ancient fossil meets modern technology

Part of a rock containing a fossil coral which is only just visible. Most of the fossil is hidden inside the rock.

Small fossils require large machines: the Diamond Light Source synchrotron facility at Didcot, Oxfordshire.

Fossils often need to be carefully prepared before they can be identified by palaeontologists and traditional methods can damage the specimen irreversibly. Scientists at Amgueddfa Cymru are experimenting with new technologies to study ancient fossils in minute detail with no damage to the specimen whatsoever.

The preparation of fossils for identification and study often requires the surrounding rock to be removed. A variety of tools are used for this, including specialist equipment such as pneumatic pens driven by compressed air and air-abrasive machines which work like miniature sandblasters. In some cases the surrounding rock can be dissolved away from the fossil

Destructive techniques

These preparation methods will reveal the surface of a fossil but to identify some specimens we must look inside them. Certain fossil groups are routinely examined using destructive techniques. For example, to study the internal structure of corals, bryozoans and brachiopods, specimens are cut up (sectioned) into slices so thin that we can shine light through them and examine them under a microscope. These slices are known as 'thin sections'.

Sometimes it is not desirable to remove the rock or to cut up the specimen. The fossil may be very delicate and break during preparation. Or, if the fossil is very rare, we would rather not use a destructive technique as it may be difficult or even impossible to replace the fossil.

Non destructive X-Ray tomography

In these instances, it is now possible to use X-rays to build up a virtual three-dimensional image. The technique is called X-ray tomography. As rock is much denser than living tissue, X-ray tomography of fossils requires a more powerful radiation source than a hospital X-ray machine. The Diamond Light Source Synchrotron at Didcot, Oxfordshire is one such facility, the only one in the UK. This machine is in the shape of a giant donut with a diameter of 300 meters. It accelerates charged particles (electrons) through sequences of magnets to almost the speed of light, producing the X-rays.

This method was recently used by Amgueddfa Cymru scientists to investigate a small fossil found in Ordovician rocks 462 million years old in Iran. It was half buried in the rock and appeared to be a solitary rugose coral. The conventional approach to identifying rugose corals – to slice into thin sections – was rejected because of the small size and rarity of the specimen. Instead we took it to Didcot for X-ray tomography.

The new technique worked very well and we managed to obtain spectacular 3D images, and even and virtual thin sections – without any damage to the fossil itself. From these, we determined the internal structure of the fossil and concluded that the specimen was indeed a coral, probably a species of the genus Lambelasma.

It is approximately 5 million years older than the earliest previously described rugose coral, making it a significant addition to our knowledge of early life on our planet.