Modes of Preservation

• Replacement


  Original material dissolved atom by atom and substituted by another
• Pyritisation


  When original material is replaced by pyrite. Only happens in anoxic environments

  Forms due to the action of Sulphur Bacteria
• Silicification


  Occurs when percolating groundwaters are rich in sulfur dioxide
• Carbonisation


  Common method of preservation of plants. Compaction squeeze's out Hydrogen, Oxygen and Nitrogen to leave a residual carbon film
• Entombment in Amber


  Emptied by certain types of Conifers

  Leads to near perfect preservation of organisms covered by it

  Mainly important for preserving insects, but also small vertebrates
• Entombment in Peat Bogs and Tar Pits

  Slow the rate of natural decay

  Anaerobic, cold conditions preserve great detail

  Pollen Grains, seeds and spores are common
• Tar Pits


  Trap animals which attract more predators and scavengers.