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PART 1B > QUATERNARY > Flashcards

QUATERNARY Flashcards

1
Q

When is the quaternary

A

the last 2.58 Ma

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2
Q

what epochs make up the quaternary

A

holocene and pleistocene

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3
Q

when was the last glacial maximum

A

29-17 ka BP

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4
Q

which ice sheets covered the N hemisphere in the last glacial maximum

A

Laurentide and Fennoscandian

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5
Q

what was doggerland

A

he connection of Britain and Europe

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6
Q

what were megafauna

A

large animals (over 40kg) that went extinct during the Pleistocene

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7
Q

what are the sawtooth of the quaternary

A

the oscillation of temp as the globe moves from glacial to interglacial

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8
Q

what was the younger dryas

A

a brief (1ka) cooling period as climate began to warm before the holocene

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9
Q

advantages of marine sediment core

A
  • deep ocean is very stable environment with undisturbed sediment accumulation over very long periods
  • deep ocean sediment cores are the longest
  • near global coverage
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10
Q

what microscopic fossil organisms are biogenic marine sediment

A

foraminifera, coccotihofores, diatoms and radiolaria

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11
Q

how do biogenic marine sediments indicate climate

A

changes in type and physiochemical composition through time. this indicates temp, salinity, nutrient availability and ice cover

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12
Q

what sort of temporal coverage do ice cores have

A

over 100ka

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13
Q

how do lake archives work and what do they indicate

A

in wash of materials through time, leading to the accumulation of sediment, biogenic components, pollen remains etc.

this indicates ecology, vegetation, landscape dynamics, hydrology, climate etc

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14
Q

define autochthonous

A

indigenous to a location rather than descended from migrants or colonists.

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15
Q

define allochthonous

A

a deposit or formation having originated at a distance from its present position

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16
Q

outline the formation of a raised bog

A
  1. shallow open lake within woodland
  2. steady infilling of the lake margins by wetland vegetation
  3. extensive colonisation of the lake by peat forming vegetation. peat now fills large parts of the original shallow basin
  4. almost complete infilling of the lake by peat forming fen vegetation. parts in the centre are waterlogged but nutrient poor because nutrients are taken by plants closer to edge
  5. low moss hummocks dominate the centre
  6. dome of peat rising as much as 10m above surrounding land has formed across the former lake, which only survives as a lag fen
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17
Q

what are the 3 types of dating methods

A
  • techniques that give relative ages
  • techniques that provide age estimates
  • techniques that give age equivalence
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18
Q

outline some radiometric dating

A

radiocarbon
potassium argon/argon argon
uranium series
lead 210
ceasium 137
luminescence
electron spin resonance
fission track

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19
Q

list annual increment dating techniques

A

dendrochronology
varve chronology
lichenometry
speleothems

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20
Q

outline some age equivalence dating methods

A

delta 18O stratigraphy
tephrochronology
palaeomagnetism
palaeosols

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21
Q

what is the law of superposition

A

in an undeformed sequence of sedimentary rock layers, the youngest layer is at the top and the oldest layer is at the bottom

22
Q

what is a proxy

A

preserved physical characteristics of the past that stand in for direct meteorological measurements

23
Q

what is a climate archive

A

a collection of data that can be used to reconstruct past climate conditions.

24
Q

what are the two main types of archive

A

marine and terrestrial (inc. ice cores) records

25
Q

what is the most difficult archive to work with and why

A

marine, sediment cores are very logistical and expensive

26
Q

+ives of marine sediment cores

A
  • gave us first detailed pic of Quaternary climate change
  • deep ocean is very stable environment with undisturbed sediment accumulation over very long periods
  • deep ocean sediment core records are the longest
  • near global coverage
27
Q

4 microscopic fossil organisms found in biogenic marine sediment

A

foraminifera, coccolithofores, diatoms, radiolaria

28
Q

abundance of O16 and O18

A

O16 - 99.8%
O18 - 0.2%

29
Q

define isotopic fractionation

A

natural processes that preferentially take up one isotope, and leave behind the other. Includes, evaporation, condensation, freezing.

30
Q

outline the spatial gradient of surface water delta18O

A

towards the high latitudes, there is reduced precipitation. this means there is more 16O but at the low altitudes there is more rainfall, so greater abundance of 18O

31
Q

how did 18O change during glacial climate

A

glaciers expand and form a new reservoir of isotopically light water on the continents, while the sea levels drop and become isotopically heavy

32
Q

drawbacks of marine isotope records

A
  • ocean temps are not globally constant
  • slow sedimentation rates mean ocean cores can reach far, but with limited temporal resolution
  • temporal resolution further limited by bioturbation
  • dating is not easy
  • individual cores can be affected by local factors
33
Q

typical sedimentation rate of deep sea sediment

A

less than 3cm/1ka

34
Q

what proxies do we get from an ice core

A
  • delta18O ratio
  • bubbles of gas allow direct measurement of GHGs like CO2 and CH4
35
Q

how are ice cores linked to geologic time

A

stratigraphical tie points

methane synchronisation

Volcanic SO4 spikes or tephra layers

Geomagnetic excursions/cosmogenic isotopes

36
Q

3 significant ice cores and their temporal coverage

A

Vostok - 420ka

Dome C/EPICA - 800ka

NGRIP - 100-123ka

37
Q

difference between lake and wetland

A

lakes are deeper and open, with no vegetation growing on surface, unlike wetland

38
Q

outline what can be used from lake and wetland archives

A
  • accumulating organic/inorganic sediments: in washed/blown materials like sediments, pollen dust
  • biogenic material living in the area like diatoms, vegetation
    *proxies for local to regional ecology, vegetation, landscape dynamics, hydrology, climate
39
Q

why are long lake and wetland records rare

A
  • high latitudes/altitudes were glaciated
  • shallow lakes fill overtime
  • challenging to date
  • challenging to retrieve cores
40
Q

online what is loess

A

wind blown silt sized sediment,
about 10% of earths surface

persistent accumulation (Ma) - long term climate signal

41
Q

what proxies are found in loess

A

magnetic susceptibility,
O and C isotopes,
pollen, charcoal, biomarkers

42
Q

how is loess commonly dated

A

luminescence, determining the last time it was exposed to sunlight

43
Q

outline magnetic susceptibility of loess during glacial periods

A

during glacial times, the landscape was dominated by erosion of bedrock and grinding of minerals by glaciers. This produces finer sediments that enhance magnetic susceptibility.

Glacial periods can introduce magnetically enhanced minerals like magnetite which are concentrated in loess

cold dry conditions lead to less biological activity, resulting in lower organic content and different magnetic properties

44
Q

outline magnetic susceptibility of loess during interglacial periods

A

warmer and wetter conditions promote increased vegetation and biological activity. This leads to the development of soil horizons and the incorporation of organic matter, which typically reduces magnetic susceptibility.

45
Q

what dating method is used for speleothems

A

U-Th

46
Q

what are speleothems

A

mineral formations found in caves, created by the deposition of minerals from dripping water.

includes stalactites, stalagmites and flowstones

47
Q

What are the main controls on the δ18O composition of forams used to create the LR04 stack? Thus, what part(s) of the climate system does the data provide a proxy for?

A

dependent upon that of the ocean water within which a foram inhabits.

ocean water isotopic composition reflects the enrichment and depletion of δ18O due to global temperature variability that drives changes in the volume of water stored on land as ice

48
Q

why does marine oxygen isoptope stack use only data from benthic forams (rather than include planktonic forams)?

A

Benthic forams live in deep-water environments (contrasting to surface-dwelling planktonic forams) and their compositions are therefore not subject to local sea surface temperature changes, but respond instead to the overall changing ocean composition driven by the oxygen isotope cycle and global ice volume.

49
Q

. Which term is commonly used to describe the shape of the glacial-interglacial cycles,

A

sawtooth

50
Q

what casts doubt on the idea of a 100kyr world

A

the length of glacial-interglacial cycles actually appears to vary between ~80-120 kyrs BP, casting doubt on the concept of a “100 kyr world” being driven by the regular 100 kyr eccentricity cycle.

51
Q
A

PART 1B (4 decks)

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