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Earth history and life - 29202 > Modes of preservation (lecture) > Flashcards

Modes of preservation (lecture) Flashcards

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1
Q

What is an example of fossils providing hidden links in evolution?

A

Archaeopteryx- (Bird with teeth or Lizard with feathers)

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2
Q

What puzzle was linked to the burgess shales?

A

That of Anomalocaris thought to be a worm/centipede until linked to Peytoia (thought jellyfish) which was the mouth and tentacle was raptoral appendages of apex predator

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3
Q

What is an example of how fossils can be important for paleoenvironmental and paleoecological studies?

A

Footprint marks of a bird found in miocene rock in the Pyrenees which shifted the idea of deep marine to shallow lacustrine

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4
Q

How can fossils be used to distinguish divergence time?

A

If A taxon group found in record followed by B we can suggest A is common ancestor but if C isn’t found to later we have to estimate using ‘ghost range’ to suggest link

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5
Q

How can fossils be used to age geological strata?

A

Can see the different fossils with their known ranges and see where they overlap to give age

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6
Q

What is the use of fossil assemblage to age geological strata called?

A

Biostratigraphic ageing

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7
Q

What are the benefits of biostratigraphic ageing?

A

Cheap, quick, accurate

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8
Q

What is needed for biostartigraphic ageing?

A

1) preservation allows identification
2) ranges are adequately known
3) fossils have not been redeposited or reworked

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9
Q

What are the 2 groups of fossils?

A

Body
Trace

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10
Q

What are body fossils?

A

partial or complete remains of plants or animals

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11
Q

What are trace fossils?

A

remains of the activityof ancient organisms such as burrows or tracks

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12
Q

What are body fossils usually like?

A

The hard parts (shells, bones, woody tissue)

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13
Q

What are the 3 common compounds of body fossils?

A

CaCO3 - calcium carbonate
SiO2 - Silica
CaPO4 - Apatite

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14
Q

What is calcium carbonate usually used to preserve?

A

corals, bryozoans, brachiopods, molluscs
many arthropods and echinoderms

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15
Q

What are echinoderms?

A

Sea urchins

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16
Q

What is usually preserved in silica?

A

Most sponges and spines of echinoderms

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17
Q

What is usually preserved in Apatite?

A

Some brachiopods and some worms

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18
Q

What are some examples of organic hard tissue that can be preserved in fossils?

A

Chitin
Collagen
Keratin

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19
Q

How can organic hard tissues exist?

A

In isolation or association with mineralised tissues

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20
Q

What is the name of the fossilisation process?

A

Taphonomic

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21
Q

What is needed for a trace of an organism to be seen in fossil?

A

the decay process needs to be arrested or inhibited

22
Q

What factors are important for decay?

A

Supply of oxygen
Temperature
pH

23
Q

What will happen to organic material in aerobic conditons?

A

microbes breakdown organic carbon by converting C and O to CO and water

24
Q

What will high temp and neutral pH do to decay rate?

A

Increase the rate of decay

25
Q

What can cause a slow of decay?

A

Unusual pH (acidity of peat bogs)
Anaerobic conditions

26
Q

What physical processes can affect fossil preservation?

A

Breakage & Diagenesis
fragmentation
in situ decay/transport/scavenging
abrasion (rolling)
disarticulation

27
Q

Why might bioerosion of fossils occur?

A

Bioerosion (borings) might occur in fossils rich in calcium carbonate which might be harvested by other organisms

28
Q

What does corrosion and dissolution of fossils lead to?

A

moulds and casts (imprint of internal and external rock structure)

29
Q

What can cause the flattening of fossils?

A

The weight of the overlying of sediment on top

30
Q

How can recrystallisation affect fossils?

A

Calcite and aragonite both CaCO3 with different minerology Calcite is more stable so the change from calcite to aragonite can destroy the internal structure

31
Q

What has recrystallisation from calcite to aragonite done to the fossil record?

A

Created a bias of calcite mineralised fossils

32
Q

What process occurs at high organic content low rate of burial for fossils?

A

Phosphatization

33
Q

What process occurs at high organic content high rate of burial for fossils?

A

preservation in carbonate

34
Q

What process occurs at low organic content high rate of burial for fossils?

A

Pyritization

35
Q

What is exceptional preservation?

A

When soft tissue of an organism is preserved in the fossil record?

36
Q

What is an example of phosphatization of exceptional preservation?

A

Preservation of arthropods (to gill filaments) in Orsten Sweden upper Cambrian

37
Q

What is an example of exceptional preservation by pyritization?

A

In Hunsruck slate, early Devonian Germany

38
Q

What is an example of exceptional preservation in carbonate?

A

Tully monster - Mason Creek , Carboniferous Illinois

39
Q

What is an example of carbonate and phosphate exceptional preservation?

A

Eel and shrimps in Granton Shrimp Bed, Carboniferous, Scotland

40
Q

What is important with exceptional preservation?

A

Some decay must occur before being removed from normal decay conditions as bacterial film act as preserving medium

41
Q

What conditions will carcasses need to be transported to for exceptional preservation?

A

Anaerobic

42
Q

What does anaerobic conditions to for fossil preservation?

A

1) Lack of oxygen means no animals on sea floor- carcasses not scavenged or damaged
2) Anaerobic environment slows decay
3) Anaerobic environment enhances growth of early diagenetic minerals

43
Q

What is an extreme example of an organism being placed in anaerobic conditions?

A

Fly in amber from tree sap (but amber only been around for 150 million years)

44
Q

What is the name of sites of exceptional preservation?

A

konservat lagerstatten

45
Q

What would the burgess shale paleoenvironment been like if konservat lagerstatten didn’t occur?

A

would be significantly less organisms to re-piece fauna

46
Q

What are the types of konservat lagerstatte?

A

Stagnation
Obrution
Traps

47
Q

What is obrution lagerstatte?

A

rapid burial

48
Q

What is traps lagerstatte?

A

instant preservation in restricted situation

49
Q

What is stagnation lagerstatte?

A

anoxic or hypersaline conditions

50
Q
A

Earth history and life - 29202 (29 decks)

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