Methods of Fossilization

Fossils are the remains of the past. During the process of fossilization, the protoplasmic contents of the cells first disappear. Then, softer parenchymatous cells begin to disintegrate, but harder sclerenchymatous or cutinized tissues try to withstand this disintegration. The growing pressure of heavy sedimentary rocks forces water and other organic substances--such as marsh gas or humic acids--to come out. The fossils are highly compressed and the final result depends upon the environmental conditions.

Compression in Sediment

• Oceans are ideal for fossil formation. When organisms die, the hard parts of their bodies settle at the bottom of the sea floor and are covered by sediment. The process of depositing sediment goes on continually and fossils are formed.

Infiltration

• The concept of infiltration suggests that the precipitation of minerals takes place, which later on infiltrate the cell walls. This process is brought about by several mineral elements such as silica, calcium carbonate and magnesium carbonate.

Natural Molds

• Organisms make impressions on mud or on sand. These impressions harden and transform into stone; these solidified impressions are known as molds.

Mummified Plants

• Plants or plant fragments are compressed by means of vertical pressure. These are called compactions, or mummified plants.

Preserved Bodies

• Sometimes the whole body of an organism is preserved. Amber, ice and tar can act as a preservative. The fossils of mammoths and saber-toothed tigers were found in Siberia preserved under ice.

Unaltered Preservation of Hard Parts

• In a few circumstances, the pores of the bones fill up with minerals, so parts of the bone remain intact. The cell walls or hard materials are replaced by silica or calcium carbonate.