Wednesday, April 22, 2015

Changing the Picture of Earth’s Earliest Fossils

Changing the picture of Earth's earliest fossils (3.5-1.9 Ga) with new approaches and new discoveries. 2015. PNAS
New analysis of world-famous 3.46 billion-year-old rocks shows that structures once thought to be Earth's oldest microfossils do not compare with younger fossil candidates but have, instead, the character of peculiarly shaped minerals.
In 1993, US scientist Bill Schopf described tiny carbon-rich filaments within the 3.46 billion-year-old Apex chert (fine-grained sedimentary rock) from the Pilbara region of Western Australia, which he likened to certain forms of bacteria, including cyanobacteria.

New high-spatial resolution data clearly demonstrate that the 'Apex chert microfossils' comprise stacks of plate-like clay minerals arranged into branched and tapered worm-like chains. Carbon was then absorbed onto the edges of these minerals during the circulation of hydrothermal fluids, giving a false impression of carbon-rich cell-like walls. PR