Fossils

Fossils...
Formed from plant and animal bodies
The plant or animal must be covered quickly after death by sediments such as mud and sand

Fossil formation

• Replacement – tissues of the dead body are dissolved and washed away by water passing through a rock.

    A cavity forms and minerals in the water passing through it come out of the solution and form a solid,      which makes a rocky shape of the body

• Petrification – water containing dissolved minerals seeps into the tissues, and minerals come out of the solution and strengthen the tissues into rock

- Georgius Agricola – German doctor, first used the word “fossil”. He used the word to describe anything that was dug out of the ground. He included ancient pottery

- Fossil was used to describe any stony animal-shaped object

Nicolaus Steno – Danish geologist, observed and compared that tongue stones are similar to a shark’s teeth.

- Index fossils – useful where sedimentary rocks have formed in the same time period but in different ways

If the same index fossil is found in both types rock, geologist can be certain that they formed at the same time and belong to the same period.

	Index fossil	Other index fossils
Quaternary	Pecten gibbus (scallop)	Argopecten gibbus
Tertiary	Calyptraphorus velatus (sea snail)
Cretaceous	Scaphites hippocrepis (ammonite)
Jurassic	Perisphinctes tiziani (ammonite)	Nerinea trinodosa
Triassic	Tropites subbullatus (ammonite)
Permian	Leptodus americanus (brachiopod)
Carboniferous	Lophophyllidium proliferum (coral)	Dictyoclostus americanus
Devonian	Mucrospirifer mucronatus (brachiopod)
Silurian	Cystiphyllum niagarense (coral)
Ordovician	Bathyurus extans (trilobite)
Cambrian	Paradoxides pinus  (trilobite)	Billingselia corrugata

 - Fossil records - Fossils also reveals different habitats, climate and conditions of the Earth that time. 

Example:

Carboniferous – damp conditions (swamps)

Permian - deserts