Preserved leaf — — thick coal layer such as in Wyoming (see car?)
Origin of Black Coal
http://unconventionalgeology.blogspot.com/2012/01/origin-of-black-coal.html
Many people think that the process of coal formation is fully understood. The paradigm is that coal is essentially a product formed through the burial of plants and, according to this conventional view, the common presence of plant fossils associated with coal deposits therefore would explain intrinsically throught biogenic origin. However, there are much evidences related to the coal origin that are not yet understood.
“The coal we dig is hard, brittle stuff [but] it was once a liquid, because we find embedded in the middle of a six-foot seam of coal such things as a delicate wing of some animal or a leaf of a plant. They are undestroyed, absolutely preserved, with every cell in that fossil filled with exactly the same coal as all the coal on the outside… The fact that coal contains fossils does not prove that it is a fossil fuel; it proves exactly the opposite. Those fossils you find in coal prove that coal is not made from those fossils. How could you take a forest and much it all up so that it is a completely featureless big black substance and then find one leaf in it that is perfectly preserved? That is absolute nonsense.”