In dinosaur fossils, bones have been mineralized.
By miracles of chance and circumstance, some plants and animals from earth's past have been preserved as fossils. From tiny bacteria 5 billion years old to giant dinosaurs, fossils give a glimpse back into time and give clues to plant and animal relationships.
Types of Fossils
Fossils are defined as any evidence of a once-living being. Besides body fossils such as skeletons, there are casts, molds, footprints, trackways and feeding traces.
First Steps in Fossilization
The remains of an animal or plant had to be quickly deposited in an area of underwater sediment or ooze where oxygen couldn't reach. Soft parts decomposed. Hard parts were protected and held in place.
Later Steps in Fossilization
Layers of sediments accumulated over enclosed organisms. Pressure cemented sediments together to become layers of rock. Fossils were infused with minerals carried by water from surrounding rocks, becoming rocks themselves. Most fossils are mineralized. Exceptions are insects and plants preserved in amber and remains preserved in permafrost, desert caves or peat bogs.
Mineralization Processes
The ways minerals can preserve fossils include recrystallization, replacement, permineralization, carbonization, impressions, casts and internal molds. Recrystallization doesn't save fine details but replacement and permineralization or petrification do.
Substances Involved in Fossilization
Fossils are commonly altered by these minerals: aragonite or calcium carbonate; calcite, a common form of calcium carbonate; silica or silicon dioxide; pyrite or fools' gold; and then the organic element carbon, as in coal.
Tags: calcium carbonate, have been, replacement permineralization, Steps Fossilization
