The decomposition of plant and animal remains in marine and non marine environments and the alteration of this debris during subsequent geologic periods by numerous reactions, produced a wide variety of carbonaceous materials. Source material and conditions of deposition were major factors influencing the types of final products formed, which range from anthracite coal to petroleum. Between these two extreme types are numerous other carbonaceous substances of different compositions and properties. Oil shales, kukersite, and torbanite represent types of carbonaceous material that contain various amounts of organic matter, commonly called kerogen, from which high yields of oil can be produced at elevated temperatures, even though the constitutions of the kerogens differ.