fossilisation Flashcards
what are the 2 types of fossils?
body fossils
trace fossils
what are the 4 types of fossilisation
silicification
replacement
carbonisation
pyritisation
percolating groundwater rich in silica dioxide moves through rock
minerals dissolved in the rock crystallise out into pores in the rock
silicification
what is 1st stage of pyritisation (1 of 3)
takes place in anaerobic environment where only alive organisms are sulphur bacteria
what is 2ndstage of pyritisation (2 of 3)
bacteria use sulphur to respire, reducing sulphur to bisulfide
what is 2nd stage of pyritisation (2 of 3)
bacteria use sulphur to respire, reducing sulphur to bisulfide
where does pyritisation occur
deep sea anoxic sea bed
shallow swamp anoxic
what is a body fossil
hard part e.g. shell
what is pyritisation
replacement of the original material with iron pyrite
what is a trace fossil
fossil of movement e.g. track
what is silicification
percolating groundwater rich in silica dioxide moves through rock
minerals dissolved in the rock crystallise out into pores in the rock
original material is dissolved atom by atom and replaced by another material
replacement
what does less stable aragonite change to
less stable calcite
why does aragonite change to calcite in replacement
because they are polymorphs
what is a polymorph
same composition minerals* (double check)
