Shale gas and oil
Gas and oil-bearing black shale formed in Ordovician and Silurian sea approx. 485 – 420 million years ago. Predominantly argillaceous mudstone sediments were deposited at the sea bottom with an admixture of organic matter. The sediments were transformed into shale rocks (shales). Under specific conditions of high pressure and temperature, the organic matter first turned into crude oil and then into natural gas.