The reserves of Oil shale and Limestone are geographically distributed all over the world. Oil shale and Limestone reserves play an important role in a country’s economic growth. Rocks are deposited according to the topography of the area. Some oldest rocks can be found in the Canadian Shield, Australia, Africa and in a few other old regions around the world. The ages of these felsic rocks are around 2.5 and 3.8 billion years. Learn about the countries with Oil shale and Limestone reserves here.