Evidence for widespread oil migration in the 1.88 Ga Gunflint Formation, Ontario, Canada

The abundance of Precambrian organic-rich shales, heated beyond the oil and gas window, requires that enormous volumes of hydrocarbons were generated and transported through the ancient crust. However, the former passage of fluid hydrocarbons rarely leaves a trace, so evidence for this process in the early Precambrian rock record is sparse. Here, we report the widespread presence of solidified oil (pyrobitumen) in the iron formation of the 1.88...