FOSSILS Flashcards
1
Q
Factors that affect fossilisation
A
- original composition - hard parts will fossilise
- diagenisis - post depositional changes
- oxygen levels - eliminates bacteria and scavengers
- rapid burial - buried before broken or eaten
- sediment size - Fine sediment = more detail
- energy levels - high energy environment destroys organisms
- transport distance - less distance = better preserved
ODORSET
2
Q
trace and body fossils
A
- trace - evidence of behaviour or activity of an organism - e.g footprints
- body - all/part of an organism - e.g shell, bone
3
Q
Preservation - replacement
A
Original material is substituted by another
- aragonite by calcite
- wood by silica (silicification)
- anaerobic bacteria (pyritisation)
4
Q
Preservation - carbonisation
A
- volatile liquids and gas are removed, leaving a thin film of carbon
- part of diagenisis
- e.g plants, graptolites
5
Q
moulds and casts
A
moulds - made of mud
casts - copy of organism
- Deposition
- Burial
- Solution
- Precipitation of new mineral
- Discovery
6
Q
Assemblages
A
assemblage - fossils of different organisms found together
death assemblage
- broken
- disarticulated
- eroded
- sorted
- aligned by current
- mixed organisms that didn’t live together
- over 90% of fossils are like this
life assemblage
- in life position
- complete
- rare
7
Q
Derived fossils
A
- eroded out of original rock
- transported (often eroded)
- redeposited in a younger rock
- e.g jurassic belmnites in quaternary till
8
Q
Marine modes of life
A
pelagic - in the water column
benthonic - in/on the substrate
nektonic - free swimming
planktonic - drifting in currents
epifaunal - on sea bed
infaunal - in substrate
9
Q
Trace fossils types
A
tracks
- footprints
- low energy environment
trails
- moving body impression
- low energy environment
coprolites
- excrement
- low energy environment
burrows
- bioturbation if soft sediment
- any energy environment
borings
- excavation of hard material
- any energy environment
10
Q
Footprints can tell you:
A
- foot structure (toes, flat-footed)
- how animal walked (bipedal or quadrapedal)
- estimated body size (in bipeds, height of hip bone = 4x length of foot)
- speed of movement (walking, trotting, running)
- how the tail is carried
