Digging through an ore deposit near Australia's rugged western coast, two geologists struck oil. They also struck scientific pay dirt: The site contains the oldest petroleum ever found and offers a peek at what Earth was like when life was new.
Sulfurous hot springs trapped the remains of ancient microbes.Photo by Dr. Roger Buick
Birger Rasmussen at the University of Western Australia and Roger Buick at the University of Sydney analyzed the microscopic oil droplets and found they are 3.2 billion years old, just half a billion years younger than the first known organisms. The discovery proves that early microbes were more abundant than formerly believed. "It takes a lot of dead bugs to produce a little bit of oil. So soon after life began, it was prolific," says Buick.
Most crude oil formed when minuscule marine organisms were slowly transformed by intense heat and pressure deep in Earth's crust. The Australian oil, in contrast, appears to have cooked quickly, probably when a plume of magma surged up beneath the ocean floor. Hot seawater above the plume would have percolated through the rocks, giving rise to both the oil and ore deposits that trapped it— a process never before observed in such old rocks. Although Buick doesn't see any economic potential from this find— "I'm not changing my name to J.R. Buick just yet," he says— it might guide petroleum geologists to useful fields in similar, though somewhat younger, geologic settings.