Evidence of 3.5 billion-year-old bacterial ecosystems was discovered preserved in sedimentary rock sequence in Australia, believed to be the oldest rock on Earth.

Scientists are always striving to unravel the mysteries behind earth's evolution. A recent discovery of very rare and oldest sedimentary rocks might help in untangling the secrets. Not only are they rare, mostly all of them are always altered by tectonic and hydrothermal activities. Researchers from Old Dominion University and the University of Western Australia uncovered well-preserved remnants of a complex ecosystem in a nearly 3.5 billion-year-old sedimentary rock sequence in Australia, according to a University release.

The Pilbara district of Western Australia is one of the most famous geological sites that provide an opportunity to peek into the evolution of early life on Earth. The discovery included mount-like deposits created by ancient photosynthetic bacteria, known as stromatolites. The microfossils of these bacteria have been described in detail in the study published in Astrobiology. What makes the discovery all the more interesting is that a phenomenon known as microbially induced sedimentary structures (MISS) was not seen previously in this region. These MISS structures form from layers of microbial material similar to layers seen today on coastal flats or stagnant waters.

The study also described many MISS preserved in the region's Dresser Formation and a chemical analysis revealed the possibility of a biological origin of the material. Researchers also noted that the Dresser MISS resembled other MISS obtained from younger rock samples from 2.9 billion-year-old ecosystem.

"This work extends the geological record of MISS by almost 300 million years," said Nora Noffke, who is also a professor at ODU. "Complex mat-forming microbial communities likely existed almost 3.5 billion years ago."