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Stratigraphy + palaeo > Stratigraphy Yr 1 > Flashcards

Stratigraphy Yr 1 Flashcards

1
Q

In 1729- 1797 James Hutton discovered what?

A
  • Deep Time ~75000 yrs
  • Using first principals saw breaks in rocks history (angular unconformity) - huttons unconformity
  • After strata are deposited they are eroded, then deposition carries on atop the strata.
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2
Q

what did james hutton think of the idea of intrusions?

A

He knew you must melt rock to make large crystals (except salt which would dissolve in water)

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3
Q

Whats the first form of intrusions

A

Invented by james hutton, the idea magma rose to the surface pushing strata aside

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4
Q

When was the rock cycle invented

A

James Hutton 1729 - 1797

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5
Q

Who came up with the extinction theory and what date?

A

Baron Cuvier in 1769 - 1832

- using elephant jaws compared to mammoths anatomy

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6
Q

What date and who was the fossil collector in lyme regis of the first what?

A

Mary Anning 1799 - 1847

- Ichthyosaurs, pleiosaurs and pterosaurs

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7
Q

Who invented the gradualism theory?

A

Charles Lyell in 1797-1875

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8
Q

What did william ‘strata’ smith create?

A

Invented lithostratigraphy and biostratigraphy

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9
Q

Who went round mapping Britain’s geology on horse back?

A

William smith 1799-1815

  • characteristic sediments with specific fossils
  • first cross sections
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10
Q

Arthur holmes is famous for?

A

Attempting to date all of geological time with radioactive decay dating.
- roughly accurate

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11
Q

Who came up with the theory of continental drift and convection currents in the mantle?

A

Arthur Holmes

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12
Q

How old is the earth?

A

~4560Ma

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13
Q

How to date what is older or younger but no actual age (relative dating)?

A
  • Fossils in each strata
  • Cross cutting relationships
  • magnetic data
  • radiometric
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14
Q

Methods of absolute dating?

A
  • Varves
  • Glacial deposits (ice)
  • Ice cores
  • Radiometric (Zircons)
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15
Q

Where can zircons be found?

A

granite or volcanic ash layers and can form round each other or be much older than the rock surrounding it.

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16
Q

Name radioactive decay:

A
  • Uranium to lead
  • K to Pb
  • Rb to Sr
  • Carbon-14 on wood/bone/charcoal
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17
Q

The lithostratigraphic hierarchy:

A
  • Supergroup
  • Group
  • Formation
  • Member
  • Bed
    Boundary is defined at the BASE of the bed.
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18
Q

Whats the name given to beds of the same age across their full geographic extent?

A

Synchronous bed

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19
Q

What is the opposite to synchronus?

A

Diachronous

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20
Q

A good fossil is common and widespread name some other factors and give examples. (biomarker)

A
  • small
  • easily preserved
  • rapidly evolving
  • distinctive
  • Forminifera (benthic and planktonic)
  • Ostrocods (tiny arthropods)
  • spores and pollen
  • acritarchs
  • conodonts
  • coccoliths
  • graptolite
  • ammonites
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21
Q

What is a biozone?

A

A geological area named after a specific fossils key characteristics. Where they begin and end

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22
Q

Name the 5 sections of geochronology:

A
  • Eon
  • Era
  • Period
  • Epoch
  • Age
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23
Q

Name the 5 sections of chronostratigraphy:

A
  • Eonothem
  • Erathem
  • System
  • Series
  • Stage
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24
Q

Whats a golden spike?

A

The point in the worlds stratigraphy where the boundary between time periods is located.

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25
Q

How did the earth moon system form?

A

Telus (primal earth) impacted a planetoid the size of mars.

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26
Q

What occurred during the Hadean?

A
  • Post impact solidifying of magma ocean a few km deep
  • New moon
  • the late heavy bombardment
  • Steam condensed in atmosphere - oceans formed
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27
Q

what does the worlds oldest zircon suggest?

A

4.37Ga continent structures and oxygen in crystal suggests water.

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28
Q

The Archean saw the beginning of what?

A
  • Rock formation (sedimentary in the oceans)

- The first single celled organisms - stromatolites

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29
Q

Describe the Archean.

A

Sun was 80% as hot, no oxygen so pyrite preserved at land surface and possible plate tectonics.
- Lewisian Gneiss formed 3Ga mountain belt 50km deep

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30
Q

What occurred in the Proterozoic?

A
  1. 5Ga - free oxygen from cyanobacteria
    - took 0.1 Ga to create atmosphere
    - Lewisian surfaced at 1 Ga followed by unconformity - torrodonian red sandstones (fluvial deposits)
    - Dalradian drop stones (Namibia) - snowballearth
    - Avalonia forming/ formed
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31
Q

What happened during the first snowball earth?

A
  • world covered in ice
  • drop stones in Namibia
  • 800-700 Ma deglaciation was rapid (glacial till covered in cap carbonates)
  • Avalonia forming/formed
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32
Q

Within 20Ma all metazoan groups appeared, name them:

A

Annelids, Arthropods, Mollusca, Brachiopods, Vertebrates

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33
Q

Why did the metazoan groups appear?

A

Oxygen levels, climate and biological grade

34
Q

What is bioturbation?

A

When burrows and disturbed sediments are fossilised

  • dont get them in anoxic condition
  • fine lamination
35
Q

The first skeletons were formed from?

A

CaCO3, phosphorous and silca

- Cloudina

36
Q

In Cambrian the first what cleaned the sea water?

A

Filter feeders, possibly more oxygen.

37
Q

During most of the palaeozoic the Iapetus ocean separated what? Closed?

A

North and south britain. It closed from the ordovician to the silurian (caladonian orogeny)

38
Q

The southern uplands accreationary prism is evidence of what?

A

In early palaeozoic ocean closure 60km thick succession of near vertical rocks (grey wache + graptolite evidence)

39
Q

In the southern uplands accreationary prism NW-SE mudstone - greywache transition becomes younger by:

A

1Ma with each thrust slice.

40
Q

The southern uplands accreationary prism thust faults were overlain by what?

A

Sandstones from the laurentian mountains.

Southern uplands eventually destroyed due to thrust faults.

41
Q

Climate change in the early palaeozoic led to:

A

Alternating beds of anoxic (warm) to oxic (cold).

- no bioturbation or benthic fauna in anoxic conditions

42
Q

The Caladonian orogeny formed mounatins in:

A

North Wales, Lake Distict and across Scotland (Especially the highlands)

43
Q

The Laurentian eroded mountains formed what continents?

A

~416Ma The ORS continent at the equator and Gondwana to the south separated by the Rheic ocean.

44
Q

The rhynie chert occured when?

A

The devonian, a bog of the first plants (sporophyte and byrophytes) and insects that collonised land.

45
Q

Devonian river deposits can include:

A

Burrows made by crustaceans and other organisms. Deposits are usually cross bedded and oxidised, overbanking muds and bogs etc.

46
Q

where to find a good example of Devonian fish bones

A

Ludlow bone bed

47
Q

Name iconic devonian fauna:

A 
Euryptends (Sea Scorpions), Armoured fish, lung fish, tetrapod ancestors.
Other fauna:
- Jawless fish
- Trilobites
- brachiopods
- Tabula/rugose corals
-Crinoids
48
Q

What occurred at the beginning of the Carboniferous

A

Marine transgression so most of UK = shallow subtropical sea.
Then major river delta came from north = millstone grit
Large tropical forests and peat bogs to create coal measures.

49
Q

Where can u find evidence for carboniferous glaciation

A

Falkland isle -boulder clays and striations

~50Ma old. - this caused cyclothems

50
Q

When did Pangaea form?

A

Permian as Gondwana moved north, closing the rheic ocean (Variscan orogeny)

51
Q

What caused the Pennines and south Wales?

A

Hercynian/Variscan orogeny during the Permian

52
Q

Due to the fact Britain was located in the center of Pangaea:

A

Very hot and arid, creation of the NRS, Salt deposits (zechstein sea) and dolomitic limestone.

53
Q

What happened during the P/T extinction?

A
  • Siberian trapps
  • chemistry of oceans changed
  • ocean anoxia
  • global warming
  • 95% species died out 50% of families
  • Trees died out an ferns colonised land in their place
  • Not alot of evidence in the UK as we are in the NRS
54
Q

Where is the Permian - Triassic boundary?

A

Meishan china, Lots of fossils of both fauna and flora to mark evidently.
- such few fossils in the UK as its all wadi conglomerate and braided rivers (mudstone, sandstone, breccia etc)

55
Q

End of Triassic there was what?

A

a marine transgression. global sea levels show it wasn’t an Isostatic change in the UK but eustatic, there was a change from NRS to shales.

56
Q

why are there varying types of ammonites found in the uk

A

in the Jurassic the UK had warm and cold water therefore we can use ammonites to bring down to 0.1Ma

57
Q

Why is there a high resolution of biostratigraphy in the jurassic

A

The ammonites evolved rapidly so speciation is very easy

58
Q

What can you find east of leicester?

A

Jurassic Oolitic limestone

59
Q

The Yorkshire coast is home to what?

A

Lias - many Jurassic fossils. Jet Rock is very carbon rich, more C-13/C-12 so indicates ocean anoxia.

60
Q

What is the name of the jurassic global ocean anoxia event that can be seen on the yorkshire coast?

A

Toarcian hyperthermal

  • very finely laminated
  • no bioturbation
  • plenty of fossils preserved
  • due to release of methane into atmosphere increasing weathering on world wide scale.
61
Q

What was in the south east (UK) in the cretaceous

A

large delta top and alluvial fan from mountains

- open antiforms and synforms

62
Q

What occurred toward the end of the cretaceous?

A
  • Sea level rose gradually, until the land was flooded - no sediment washing into the sea - chalk deposits form as deep sea ooze of coccoliths = biogenic.
  • CO2 increase poles melted
  • Chalk is white as no sediment, all CaCO3
  • flint bands of pure silica
63
Q

Give evidence for the K/T extinction

A
  • Iridium layer
  • glass spherules as rock vapourized on impact and condensed in atmosphere
  • shocked quartz - laminae in quartz (Australia)
  • Gravity anomaly
  • impact melts and huge glass layer
  • Deccan Trapps, India.
64
Q

Name and date the 3 epochs in the Palaeogene

A
  • Palaeocene 65Ma
  • Eocene 55Ma
  • Oligocene 35Ma
65
Q

Name and date the 2 epochs in the Neogene

A
  • Milocene 25Ma

- Pliocene 5Ma

66
Q

Describe the tertiary ecosystem?

A

The land is covered in mammals from all sizes and angiosperms, the sea is full of bivalves and gastropods. Giant formanifera and more of a modern ocean floor.

67
Q

What name and size are the giant tertiary formanifera?

A

Nummulites and size of 1p

68
Q

What occurred around 34Ma

A

A huge climate change as antartica changed from climate like New Zealand to what it is today over ~200000yrs.

69
Q

What happened geographically in the early Cenozoic?

A

Antartica broke away from australia and south america.
- resulting in circular cold polar current.
Closure of the tethys ocean and later the panama isthmus.
- stopping warm current at equatorial latitude.
- overall sea level drop of 300m

70
Q

What was the magnitude of the drop in CO2 levels during the Palaeogene and when did it occur?

A

Eocene and Oligocene boundary there was a drop from 800 ppm to 400 ppm

71
Q

At 55Ma what happened in the north sea?

A

The North Sea triple point formed leading to the north west Scotland Tertiary igneous province.

  • flood basalts
  • Gabbroic intrusions
  • Granite intrusions
  • Dyke swarms
72
Q

Erosion in the Northern mountains meant:

A

As the UK tilted to the SE deposition occurred in the North Sea basin.

73
Q

Where is there strong evidence for the Alpine orogeny?

A

Isle of wight, Near vertical folded succession.

74
Q

What evidence is there of the late Neogene 3Ma environment?

A
  • London clay indicates subtropical climate.
  • Crag deposits 1/2km thick in east anglia indicative of a shallow sea. (rich in bryozoan fossils, shells indicate similar temp to today.
  • Cross bedded sediments, like tidal dunes. suggests N.Sea a few km inland from today.
75
Q

How long is the Quaternary?

A

2.6Ma

76
Q

What was the initial idea for the quaternary geology formation and when did it change?

A
  • Idea of a deluge ~200yrs ago.
  • Ice theory in 1820-1830 but controversial
  • Evidence like striations and u-shaped valley after studying the Alps.
  • Accepted by end of 1800’s.
77
Q

What was suggested in the 1950’s?

A

4 glaciations separated by warm interglacials, it was clear from till differences.

  • Land deposits were patchy and incomplete so drilled into ocean floor for O2 isotope data.
  • This gave evidence for temperature and global ice volume
  • 50 major glaciations in quaternary
78
Q

What are the three processes of the Milankovitch cycles? Describe them.

A

Eccentricity - change from near circular orbit to elliptical , 100000yrs
Obliquity - variation of the tilt of the earths axiz through the planet, 40000yrs
Precession - movement of the axis in a circular motion (like a wobbling spinning top), 20000yr cycle.

79
Q

What are some problematic factors for the Milankovitch cycle?

A
  • Changes in the amount of sunlight are very small, not enough to cause such big changes
  • An Amplifying factor - represented by greenhouse gases
  • Ice core record indicates amplification of milankovitch signal via G.gases
80
Q

Describe the Pleistocene epoch.

A

Almost all of Quaternary made up of this,
- Bipolar ice ages across north and south hemisphere
- Deposits like till + outwash gravel/sand show two different advances of the ice
(straightline S.UK 400ka) and (humpback further north 20ka)

81
Q

Describe the Holocene epoch.

A

The last 11.6ka

  • time of stability (allowing us to develop)
  • Transitions
    • sudden warming for 2000yrs
    • abrupt cooling 1000yrs
    • Abrupt warming
    • sea level rise by 130m
  • deposits from present day (soils flood deposits, deltas)
82
Q

What factors do we consider when contemplating the Anthropocene?

A

Chemistry change in oceans and atmosphere, concrete levels, temperature, sea ice, Extinctions.

Stratigraphy + palaeo (3 decks)

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