What sedimentary rocks have plant fossils?

Answer 1

Although any sedimentary rock can contain plant fossils, the fossils themselves are likely to be coal. Coal itself is a sedimentary rock, and this is entirely composed of plant fossil, but for the physical evidence of the existence of a plant, you would be lucky to find an intact sample, as after the death of the plant it crumples and wilts, and then sedimentary processes crush it. It is estimated that for every metre of coal measure, there was 20 metres of plant material. Any rock can contain a plant fossil, but it is rare to find a plant fossil outside of a coal measure.

An example of a plant fossil outside of a coal measure would be a bed of shale with a root-like structure in it. This could be in-filled with any soluble mineral. The history would be that the shale was uncovered by natural processes, it had a crack in it, a seed fell into the crack and the tree grew inside the crack, spreading its roots. Later, after the tree died and rotted away, the impression was in-filled and thus preserved.