Adding a little to the article, peat is dead plant material that has accumulated in a wet, anoxic (oxygen-poor) environment. Buried deeply by sediments, it is converted to coal by heat and pressure.
A lignitic coal is the next stage; the fuel has been used in several states, including Texas. There is a bed in Arctic Canada that caught fire and has been burning for many years; it was laid down when the earth's axis was at an inclination permitting much higher temperatures (think the Carolinas) in the Arctic.
Peat beds may vary in thickness, up to many feet. When buried by succeeding sediments, they are compressed and feet of thickness become inches.