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Palaeobiology > L3 > Flashcards

L3 Flashcards

1
Q

Why is it important to understand the rock record?

A
  • We can then better interpret the fossil record
  • Provides more insightful window into fossil
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2
Q

What are the two types of extraordinary fossil occurrences, Lagerstatten?

A

Concentration deposits

Conservation deposits

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3
Q

Concentration deposits

A
  • Fossils occur in unusual concentrations
    • Examples include bone beds and mass kills eg ponds
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4
Q

Conservation deposits

A
  • Exceptional preservation
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5
Q

Three basic types of exceptional preservation in conservation deposits:

A
  1. Preservation of organisms that are not normally preserved
  2. Preservation of parts of organisms that are not usually preserved
  3. Organisms are preserved unusually articulated or in unusual configurations
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6
Q

Preservation of organisms that are not normally preserved

A
  • Perfectly preserved in phosphate (phosphatised)
    • Eg embryos
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7
Q

Preservation of parts of organisms that are not usually preserved

A
  • Eg skin
    • Unoxygenated zones
    • No life to destroy carcus
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8
Q

Organisms are preserved unusually articulated or in unusual configurations

A

Eg happens with quick burial

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9
Q

What permits exceptional preservation? (2)

A
  1. The exclusion of scavengers and bioturbators (anoxia, rapid burial, elevated salinity)
  2. Unusual chemical environments permitting exceptional preservation
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10
Q

Unusual chemical environments permitting exceptional preservation

A
  • Create microchemical environments when rotting
    • Promote crystal growth which can help exceptional preservation
    • In tandem with bacteria that produces gases etc
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11
Q

Exceptional preservation often results from…?

A

a catastrophic event such as rapid burial or deposition and/or in an unusual chemical environment. In the latter: nodule formation may be important:

- Microbial mats may be important forming a death mask (stabilise sediment and set up geochemical gradients that promote early mineralisation)
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12
Q

Exceptional preservation methods: (6)

A
  1. Amber
  2. Ice
  3. Tar pits
  4. Hot silicious springs
  5. Tufa
  6. Ash falls
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13
Q

Amber

A
  • Sticky resin catches insects, plants, hairs etc
    • Incorporates organism
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14
Q

Ice

A
  • Preserved
    • Record not that old
    • DNA is preserved, helps with taxonomy to certain elephant species
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15
Q

Tar pits

A
  • La brea
    • Water rests on tar
    • Animals go in and get trapped
    • Only bones (no skin)
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16
Q

Hot silicious springs

A
  • Silica precipitates out and forms sheets trapping plants etc
17
Q

Tufa

A
  • Acidity of water dissolves limestone
    • This drips down and preserves
18
Q

Ash falls

A
  • Deposits explode and move down volcanoes at speed
    • Perfect preservation
19
Q

The actual process of preservation

A
  • Fossils becomes saturated with water
    • Water gets expelled and the minerals within it precipitate in the void between sediment gluing it together
    • Fusion points of pressure in the sediment
    • Shell can either in water or leave a mold
    • Shell forms in precipitated crystals
    • Play-off of precipitation of minerals along with actual fossil being preserved/replaced
    • Occasionally loads of mineral precipitates to form a nodule protecting the fossil eg chalk
    • Living aspect of animal rots away and area around the fossil has a sealed chemical environment
20
Q

Recalcitrant is on a spectrum from:

A

Teeth, bones to labile (muscle, eyes)

21
Q

Decay prone tissues are only preserved when they are replicated … ?

A

Rapidly by authigenic materials, these are:

1. Bacteria replace tissue and precipitate fossils entombing and mineralising themselves

2. Microbes mineralise themselves 

3. Microbes can form a 'death' mask
22
Q

What is the best mineral for preservation?

A

Apatite (phosphate)

- Good for preservation
- Comes from organisms when they die
- Natural precipitation fills in gaps
23
Q

Does exceptional preservation have to happen quickly or slowly?

A

Quickly

24
Q

Where do clay minerals occur?

A
  • In cold and glacial locations
  • Low pH environments
25
Q

Some periods of high phosphate in deep past:

A
  • Phosphate built up and not used in the past as it is in shortage
    • Structures can be perfectly preserved by replacement of phosphate
    • Phosphate rich environments do not form today
26
Q

Exceptional preservation may also result from:

A
  1. Iron pyrite
    - can replace organs
  2. Other metal sulphides
  3. Silica
    - Often forms nodules
    - Good for wood
  4. Calcite
    - Coal balls precipitate out and perfectly preserve
27
Q

What often accumulates around an organisms nucleation point?

A

Concretians - these are very important in exceptional preservation

28
Q

How can fossil lagerstatten confuse us/ be biased? (3)

A
  • False biodiversity peaks
    • Preferentially occur during certain periods of geological time (eg Cambrian)
    • Eg no bioturbators at certain periods etc
    • Certain unusual environments are over represented
    • Eg bias as they happen to preserve very well
29
Q

Messel (Cenozoic: Germany)

A
  • Lake formed by volcanic activity
    • Plooms of CO2 build-up, kills anything nearby due to carbon monoxide poisoning
    • Animals flying over etc then die and get preserved
    • Different tissues preserving in different ways, this happen in close proximity
    • This happens because of the micro-environments and chemical compositions
30
Q

Hunsruck slate

A
  • Shallow sea anaerobic
    • Iron pyrite preservation
31
Q

Jehol biota: Cretaceous, China

A
  • Large series of lakes
    • Rock accumulates in lake and causes ash beds upon eruption
    • Ash beds cause micro environments below causing exceptional preservation
    • In between ash layers there is normal preservation of animals
    • Internal organ preservation at bottom of the ash layers
    • Pushed down due to volcanoes

Greater knowledge acquisition due to detail

32
Q

What can the Jehol biota tell us about Behaviour?

A
  • Behaviour can be observed from preservation
  • Eg swimming with young
33
Q

Ptesours have…?

A
  • Feathers with integuments on wings
34
Q

Feathers

A
  • Birds were taken out of the sky
    • Feathers don’t have a great fossil record but are preserved here by ash
    • Dinosaurs were found, providing evidence that some dinosaurs have feathers
    • Feather colour can also be revealed using an SEM

Palaeobiology (15 decks)

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