Sun Dec 04 14:20:54 CAT 2016

Ancient fossil find in Northern Cape rocks geologists' world

Dave Chambers | 2016-11-30 17:41:36.0
Fossils found in 2.5 billion-year-old rocks near Kuruman show microbial life was thriving long before the atmosphere became rich in oxygen. The large, spherical structures are far larger than modern bacteria, and survived by oxidising sulphur.
Image by: Andrew Czaja, University of Cincinnati

South Africa already has the Cradle of Humankind‚ and now it can boast of being the cradle of some of the earliest life on Earth.

Tiny bubble-like structures found in ancient rocks near Kuruman in the Northern Cape show life was thriving in the harshest of conditions billions of years ago.

Fossils of the ancient bacteria date back 2.5 billion years‚ long before the planet’s atmosphere became rich in oxygen.

Researchers including Nicolas Beukes‚ a University of Johannesburg geologist‚ believe the sulphur-consuming microbes are the oldest of their kind yet discovered.

Beukes's team‚ led by geologists from the University of Cincinnati in the US‚ uncovered the fossils during field expeditions in what is known as the Gamohaan Formation of the Kaapvaal craton.

They believe they belong to bacteria which lived in the ocean depths off a former supercontinent called Vaalbara‚ feeding on sulphur compounds seeping through cracks in the Earth’s crust.

Isotopes in the rocks were dated to 2.52 billion years ago‚ making the fossils the earliest known evidence of sulphur-oxidising bacteria.

Samples collected in Kuruman indicate that microbes lived in the depths of the early oceans between 2.8 and 2.5 billion years ago.

What makes the recent find so important is the rarity of billion-year-old rocks dating back to the Earth’s ancient past‚ with only a few sites in South Africa and Australia.

“These are the oldest reported fossil sulphur bacteria to date‚” said University of Cincinnati geologist Andrew Czaja.

“They likely consumed the molecules dissolved from sulphur-rich minerals that came from land rocks that had eroded and washed out to sea‚ or from the volcanic remains on the ocean's floor.

“These fossils tell us that sulphur-oxidising bacteria were there 2.52 billion years ago‚ and they were doing something remarkable."

The findings are published in the journal Geology‚ and the researchers say that studies of the ancient microbes could help to build more accurate models of the early Earth and the compositions of its atmosphere and oceans.

TMG Digital/Cape Newsroom

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