Fossils Flashcards
How are fossils formed?
Body survives long enough after death to undergo fossilisation
Remains must become buried in sediment at the bottom of a water column
types of fossils
Igneous- form in volcanoes
Sedimentary- form under water
Metamorphic- form under ground
where are fossils found?
in sedimentary rocks
what does fossils quality depend on?
State of body at start of process and geological factors
what is relative fossil dating?
comparing with fossils of a known age
Radio-carbon dating
5730 years after death ½ the C14–> N14
Can work out date of death by examining ratio
Only for fossils up to 40,000 years old
volcanic ash detection
Many sediments contain volcanic ash (‘tephra’)
Potassium and argon
Decay more slowly than C14- fossils older than 100,000 years
paleomagnetic dating
Currents in Earth’s core change direction of magnetic field ‘Normal’ / ’Reversed’
Determines alignment of magnetic particles when rocks form
Age rocks by comparing the polarity of sediments to cores of rock from sea bed
fossil butterflies
65 myr bp
mammals diversify
65 myr bp
cretaceous period
65-144 myr bp
jurassic period
144- 206 myr bp
triassic period
206-251 myr bp
permian period
251- 290 myr bp
carboniferous period
290- 354 myr bp
Devonian period
354- 417 myr bp
extinction of most dinosaurs
cretaceous period
melanosomes
contain the pigment in hair and feathers
‘quarry dinosaurs’ lived in this period
Jurassic period
triassic period known for
“age of reptiles”
ammonites
molluscs with a hard shell
fusulinids
protists with a hard shell
permian period known for
terrestral tetrapods, arthropods, plants and fungi
carboniferous period known for
“giant insects”
when was atmospheric oxygen 80% higher than today
Carboniferous period
“age of fishes”
Devonian period
silurian period
417- 443 myr bp
ordovician period
443- 490 myr bp
Cambrian ‘explosion’
490- 543 myr bp
when did fish evolve and diversify
Silurian period
