Fossil Preservartion Types

Question 1

Replacement

Answer 1

Occurs when original material is dissolved atom by atom and substituted with another material

Question 2

Silicification

Answer 2

Silica minerals dissolved in groundwater percolating through the rock crystallise out of solution and fill any pores or voids in the rock

Question 3

Carbonisation

Answer 3

Overlying mass of rock increases the temperature and pressure causing volatiles to be driven off, increasing overall carbon content

Question 4

Pyritization

Answer 4

Replacement of original material by iron pyrites. Takes place in anaerobic environments where bacteria use sulphur to respire, reducing sulphur to bisulphate which reacts with iron in the environment to form iron pyrites which replaces the fossil material

Question 5

Mould and cast formation

Answer 5

Moulds are formed when fossils are dissolved out of the rock they are in, leaving a void in the rock. A cast is formed when the mould is in filled with another mineral