Scientists Unlock Nature’s Secret Preserver – Fool’s Gold

Scientists have made a rare discovery from over 500 million years ago that provides new information on how a record of the past was perfectly preserved by nature.

Geologists at the University of Leicester have found that pyrite – or fool’s gold – replaced soft tissues, thereby preserving animals to their smallest details for posterity.

Dr Sarah Gabbott and colleagues, of the University of Leicester Department of Geology, found creatures with the very hairs on their legs preserved and, in some cases, the contents of their last meals could be identified in the guts of animals. Details of how pyrite preserves these ancient creatures were published this month in Geology, published by the Geological Society of America.

Dr Gabbott said: “In the Yunnan Province, China, the Chengjiang sediments have contained within them unique and exquisitely preserved fossils. Although these animal remains are over 500 million years old nearly every detail of their anatomy can be studied, from the spiny proboscis of ancient worms to the hairs on the legs of primitive arthropods. These animals lived in the Cambrian sea and record what life was like just after the Cambrian ’evolutionary explosion’ – a crucial time in the history of life on Earth.

“Until now the processes that acted to preserve these animals have been poorly understood. Our study shows that a common mineral, pyrite (often known as fool’s gold) rapidly precipitated onto the rapidly decaying carcasses of the Chengjiang animals and faithfully captured their morphology.

“If pyrite had not replaced these tissues all of the fossils simply wouldn’t exist as many are entirely made from easily decayed soft tissues. If we didn’t have these animals preserved we would have no idea of the weird and wonderful animals of the Cambrian seas, more than 500 million years ago.

“Even more remarkable is that the type of soft tissue may have influenced the shape of the mineralizing pyrite crystals. Raspberry shaped pyrites, termed framboids, replaced easily decayed animals and tissues, whereas, perfect octahedral and cubic shapes reflect animals and tissues that were tougher and so decayed more slowly.”