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The following points highlight the top ten methods of fossilization. The methods are: 1. Petrifaction or Premineralization 2. Mold and Cast 3. Carbonization 4. Trace Fossils 5. Coprolites 6. Preservation 7. Compression 8. Natural Molds 9. Mummified Plants 10. Infiltration or Replacement.
Method # 1. Petrifaction or Premineralization:
Rock like minerals seep in slowly and replace the original organic tissue.Silica calcite or pyrite, forming a rock like fossil. This method of fossilization can preserve hard and soft parts. Most bone and wood fossils are premineralised.
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Method # 2. Mold and Cast:
A replica of a plant or animal is preserved in sedimentary rocks. An organism is buried in sediment and then dissolved by underground water leaving a hollow depression is called a mold. The mold shows only the original shape and marking of the organisms. It does not reveal the internal structure. Minerals or sediment fills the hollow depression and forms a cast.
Method # 3. Carbonization:
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Fine sediments enclose a delicate matter such as leaves in an oxygen poor environment. As time passes, pressure squeezes out the liquid and gaseous components of the organism leaving behind a thin residue of carbon. Other elements like oxygen, hydrogen and nitrogen are removed.
Method # 4. Trace Fossils:
Fossils are formed by the traces left in the rock by an animal such as:
(i) Tracks:
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Animal foot print made in soft sediment that later formed solid sedimentary rock.
(ii) Burrows:
Animal trails made in soft sediment that later formed solid sedimentary rock.
Method # 5. Coprolites:
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Fossil dung (feces) and stomach contents in soft sediment that later form solid sedimentary rocks. Fossilized drooping, can give an insight into the feeding behavior of animals and can therefore be of great importance.
Method # 6. Preservation:
Original remains can be preserved in ice or in amber (tree sap). Both ice and amber protect the organisms from decay (oxygen free environment). The entire animal has been preserved, even the soft parts when usually decay and disappear.
Method # 7. Compression:
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When organism dies, the hard parts of their bodies settle at the bottom of the sea floors and are covered by sediment. The process of sedimentation goes on continually and fossils are formed.
Method # 8. Natural Molds:
Organisms make impressions on mud or on sand. These impressions harden and transform into stone. These solidified impressions are known as natural molds.
Method # 9. Mummified Plants:
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Plants or plant fragments are compressed by means of vertical pressure. These are called mummified plants.
Method # 10. Infiltration or Replacement:
The precipitation of minerals take place which later on infiltrate the cell wall. The process is brought about by several mineral elements such as silica, calcium carbonate and magnesium carbonate. Hard parts are dissolved and replaced by these minerals.
