The Burgess Shale of British Columbia is arguably the most important fossil deposit in the world, providing an astounding record of the Cambrian "Explosion," the rapid flowering of complex life from single-celled ancestors. While most of the fossil record is comprised of shells, teeth and bones, the Burgess Shale preserves the softer bitsthe eyes, guts, gills and other delicate structuresof animals belonging to Earth's earliest complex ecosystems a half a billion years ago. The process for this extraordinary preservation remained a mystery since the initial discovery of the Burgess Shale in 1909 until now.
A team of researchers led by Robert Gaines, of Pomona College (USA), and Emma Hammarlund, of the Nordic Center for Earth Evolution (Denmark), claims to have unlocked the mystery of the Burgess Shale in their study, "Mechanism for Burgess Shale-type preservation," published in Monday the 5th of March in the Proceedings of the National Academy of Sciences. In addition to Gaines and Hammarlund, the team includes researchers from t Yunnan University (China), the University of Leicester (UK) and Guizhou University(China).
The team collected evidence from the Burgess Shale, two new drill cores from the Chengjiang deposit in Yunnan Province, China, and from five other principal Burgess Shale-type deposits in Utah and China. Using geochemical analysis involving the sulfur isotypes from pyrite (fool's gold), they found a striking global pattern that unlocks the key to the unusual preservation process.
The process begins with the very rapid burial of organisms in mud layers with little to no oxygen. The critical discovery by the research team was a layer of calcium carbonate cement, in all of the sites, laid on the sea floor soon after burial of the fossils in mud. This mineral carpet acted as a barrier to the microbial communities that would normally consume soft tissue organisms in two-three weeks. Because the microbes were prevente
|Contact: Emma Hammarlund|
University of Southern Denmark