A team of Australian scientists has discovered the world's oldest oil in 3 billion-year-old rocks from Australia, South Africa and Canada.
Their discovery suggests that oil-forming microbes were both active and plentiful at a time not long after the origin of life itself. Indeed, the oil-forming bacteria may be among the most primitive and earliest inhabitants of the Earth.
The team, Dr Adriana Dutkiewicz of CSIRO Petroleum, Dr Birger Rasmussen, University of Western Australia and Dr Roger Buick, University of Sydney, published their findings today in the international scientific journal Nature.
Using a novel combination of fluorescence and electron microscopy, the team discovered tiny drops of oil preserved in the rocks. Until now, the oldest known oil had been dated as 1.5 billion years old," says Dr Dutkiewicz.
"By extending the age of the preserved oil, we have added new insights into the early evolution of life and have greatly expanded the area for petroleum exploration.
"We found the oil preserved within fluid inclusions, which are microscopic-sized droplets of fluid trapped within mineral grains, similar to gas bubbles trapped in ice cubes. Most of these inclusions measure less than a hundredth of a millimetre across and are recognised by their fluorescence under ultraviolet light," she says.
The study was done on thin-sections of these rocks. The sections must be just the right thickness to protect the inclusions and yet allow light to shine through.
"We thought the rocks would be too old to reveal anything like this. But when you look down the microscope, you see these tiny oil droplets light up like a Christmas tree", Dr Dutkiewicz says.
"Oil generation early in Earth's history was evidently widespread since we found these objects preserved in rocks from three continents.
"The study reveals that aquatic life at the dawn of evolution was more abundant than previously thought.
"It's quite amazing when you consider that the oldest rocks are 3.8 billion years old and the oldest fossils 3.5 billion years old
"This ancient oil can potentially yield valuable information about the early biosphere, especially if it turns out to contain molecular fossils (biomarker molecules) of the primordial organisms from which it was derived", she says.
This study opens up a new area of research for scientists and exploration companies alike. To find new oil reserves, petroleum explorationists will be forced to look in unconventional places and exceptionally old rocks may well turn out to contain oil reserves.
More information :
Dr Adriana Dutkiewicz, CSIRO Petroleum 02 9490 8924,A.Dutkiewicz@dpr.csiro.au
Dr Roger Buick, University of Sydney 02 9351 2032, buick@es.su.oz.au
Dr Birger Rasmussen
University of Western Australia 08 9380 2666