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Palaeobiology > L5 > Flashcards

L5 Flashcards

1
Q

Time is sub-divided into a …?

A

Temporal framework

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2
Q

Temporal framework

A
  • Time is sub-divided in a temporal framework
    • Different periods of time were of unequal length
    • Subsequently dated by rock and ash analysis
    • Period, epoch, stage, sub-stage
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3
Q

Continental configuration

A
  • Varies due to continental drift
    • Iron minerals align towards the poles by studying these we can work out continental positions
    • Rocks from certain time slices can calculate palaeogeography

Steps:

- Work out continental position

- Plot sedimentary rocks

- Recreate paleogeographic maps
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4
Q

How can we work out continental positions?

A

Iron minerals aligning towards the poles

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5
Q

Sea level variation

A
  • Sea level and continental configuration have changed over time in both the long and short term, meaning that the extent of shelf seas and epicontinental seas (shallow seas on the continents) has varied considerably
    • Sea level curve
    • Little shelf if sea levels are low, as continents are exposed
    • Icehouse world causes shallow sea levels, greenhouse world causes much higher sea level
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6
Q

If sea levels are low, shelf cover is …?

A

Low - continents are exposed

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7
Q

Two schools of thought regarding reconstructing past environments

A

Catastrophists

Uniformitarians

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8
Q

Catastrophists (3)

A
  • Earth’s history was punctuated by catastrophic events
    • Guided by religious principles
    • Assumed Earth was young
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9
Q

Uniformitarians

A
  • Earth is constant
    • Assumed Earth processes are the same as in the past
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10
Q

We know surface processes are governed by physics however we also know: (facts about Earth)

A
  • Earth has been moulded by catastrophic events and is very old
    • Earth has been very different environmentally in the past
    • Natural change eg icehouse ages and human shaped change
    • Reconstructing fossil environments may provide good insight into past environments
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11
Q

Past environments may be interpreted using: (5)

A

1 The nature of sediments
2 The nature of fossil content
3 The distribution of climatically sensitive sediments and fossils
4 Environmentally discriminating isotopes
5 Environmentally influenced characteristics of organisms

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12
Q

The nature of sediments

A
  • Computer modelling
    • Wind deposits
    • Characteristics of sediment
    • Work out directions etc
    • Enable developed stories regarding eg sea level rise
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13
Q

The nature of fossil content

A
  • Identifying species eg marine species on land helps identify environments, therefore what was once marine
    • The distribution of climatically sensitive sediments and fossils show environment from tropical to cold etc
    • Certain fossils predispose themselves to certain temperatures
    • New environments don’t necessarily represent old environments
    • More sites for plotting, pull of the present so more of an accurate reading
    • Can draw where what shall occur
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14
Q

4 Environmentally discriminating isotopes

A
  • When organisms build shells or exoskeletons cuticles etc
    • Built from surrounding environment
    • Compounds that allow for synthesis preferentially uptakes certain types of carbon
    • Eg on temperature and acidity
    • Composition of shells etc means we can then work out past temperatures etc
    • Certain shells include boron hydroxide
    • -Isotopic composition of boron can be calculated
    • We can relate this to ocean acidity
    • Ocean acidity is governed by CO2

We can then calculate CO2 levels

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15
Q

Environmentally influenced characteristics of organisms

A
  • Many organisms have traits that vary depending on the environment
    • Wood is perfectly preserved
    • Know trees lived in seasonal environments
    • Ostrocod shape varies on salinity
    • Same species changes shell morphology
    • Can work out different environments eg salinity of environments
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16
Q

Modelling

A
  • Study Earth climate today and apply it to the past
    • Deeper in the past the less effective this modelling is due to more world differences
    • Useful comparisons to climatically sensitive organisms
    • Certain properties are apparent eg closer to poles is colder
17
Q

What was the environment in which the dinosaurs lived like?

A
  • Single continent of pangea
    • Super continent
    • Triassic
    • Once continents become separated so do dinosaurs
18
Q

Continental drift and the dinosaurs

A
  • Continents began to fall apart early Jurassic
    • Whole groups of dinosaurs split with continental drift
19
Q

Atmospheric composition the time of dinosaurs

A
  • Soil chemistry
    • Stomatal density of plants
    • Dinosaurs were in an area of higher CO2 greenhouse world
    • CO2 curves have a large range of error to be aware of
20
Q

Oxygen at the time of dinosaurs

A
  • Present O2 is high
    • O2 gets higher throughout dinosaur reign
    • Starts off low for dinosaurs
    • Important
    • Elevation thins out CO2
    • Therefore low O2 was tricky at low elevations eg peak district
21
Q

Temperature at the time of dinosaurs

A
  • Dinosaurs lived in a relatively warm world, high sea levels
    • Plotting climatically sensitive indicators can work out time slices of the type of world dinosaurs lived in throughout their reign
    • Most of history is a greenhouse world
    • We are currently in an ice- house world
22
Q

Polar dinosaurs

A
  • No ice sheet north or south pole
    • Winter and summer at the poles due to Earth tilt
    • Ice free but sixth months polar winter, then six months polar summer
    • Earth had a higher CO2 content so no ice
    • Was cold temperate at the poles in past time
23
Q

Plate tectonics and dinosaurs

A
  • Dinosaur remains found in artic
    • Many in siberia, alaska
    • Southern sites in new zealand, Australia
    • Many sites show dinosaurs existed in high latitude environments
    • Sediments shows the land did freeze in winter, however defrosted again in summer
    • This areas are associated with lots of plant fossils
    • Forests grew at high latitudes were inhabited by dinosaurs in winter areas
    • Plants were alive half the year then hibernated the other half
    • Just because a habitat doesn’t exist today, doesn’t mean plants cannot tolerate it
    • Plants benefitted from this method
24
Q

Did dinosaurs exist in high latitude environments?

A

Yes

25
Q

How did the dinosaurs survive in artic winter?

A
  • Cold (ice heave and polygon structures associated with bones)
    • Polar winter (moon helps)
    • Possible evidence for migration in the North out of cold forests in winter and back in, in summer but not possible in the south
    • Large eyes suggest dinosaurs adapted for polar winters to see in the moonlight
    • No evidence for burrowing (hibernation) No LAGs
    • Warm blooded? spectrum
    • Integumentary structures for warmth?

^ this is unknown

Palaeobiology (15 decks)

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