Describe the four types of fossils?

Types of fossils

Usually the remains of dead plants and animals quickly decay and are

destroyed. When the remains are protected from scavengers and

micro-organisms, however, they can become fossilized.

If a carcass is in water and sinks to the bottom, the body can be

buried by sediment. Soft parts, such as skin, muscle, or organs decay

rapidly and are rarely found as fossils. The hard parts (bones, shells,

or teeth) may be altered to become fossilized remains. When water

penetrates the bones of a dead animal, the water dissolves the calcium

carbonate in the bones. A deposit of another very hard mineral, silica

(quartz) remains, turning the bones into a petrified (rock-like) substance.

When an organism is buried under many layers of sediment,

pressure and heat may build up, leaving a thin film of carbon residue

on rock surfaces. The residue forms an outline of the organism. The

outline is called a carbonaceous film.