Upper Palaeozoic in the British isles Flashcards

1
Q

What orogeny occurred in the Devonian to the Carboniferous?

A

Variscan (rheic ocean closing)

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2
Q

What had an influence on the shape and geometry of the variscan orogeny?

A

The Caledonian orogeny

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3
Q

What is the chronology of the Devonian?

A

416-359 Ma

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4
Q

What rock formation was established in the devonian?

A

Old Red Sandstone (ORS)

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5
Q

What was the paleoenvironment of Britain in the Devonian?

A

Largely non-marine
Marine in South/ South West

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6
Q

What was the continental configuration of the Devonian?

A

Great southern continent (Gondwana)
With large continental area of South pole

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7
Q

What are some non-marine basins of the UK Devonian outcrop?

A

Anglo-Welsh Basin
Caledonian Basin
Orcadian Basin

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7
Q

What present day continents made up Gondwana?

A

South America
East Antarctica
NW, NE and S Africa
India
Arabia

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8
Q

How can the thickness of the Devonian successions in the UK be described?

A

Extremely thick (South wales basin ~7000m)

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9
Q

What are the characteristics of the Devonian basins in the UK?

A

Fluvial and alluvial sediments
Sandstones, conglomerates and mudstones
Abundant calcretes
Some lavas
Middle Old Red Sandstone

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10
Q

What are calcretes?

A

Soils with carbonate concretions- evaporating conditions

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11
Q

What is the oldest part of the black mountains in Pembrokeshire?

A

Brownstones (mainly sandstones and conglomerates)

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12
Q

What is the Devonian deposition at freshwater west Pembrokeshire like?

A

Red sandstones, Conglomerates, Calcretes
Beaconite trace fossils

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13
Q

Where is the Orcadian basin in the UK?

A

NE Scotland

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14
Q

What does Orcadian basin show evidence of?

A

Cyclicity

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15
Q

What is the upper devonian stratigraphy like in the Orcadian basin?

A

breccias, volcanics at base, fluvial sandstones,
conglomerates & calcretes above

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16
Q

What is the Middle devonian stratigraphy like in the Orcadian basin?

A

fluvial & then lake sediments
* sun-cracked mudstones
* sandstone
* impure limestone, with freshwater fish

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17
Q

What evidence can be gathered for the Orcadian basin?

A

Well preserved fish
Arid varves indicating seasonal variability

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18
Q

What is the marine devonian basin in SW England called?

A

Culm basin

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19
Q

What extinction events occurred in the Devonian?

A

Kellwasser (Frasnian)
Hangenberg (Famennian)

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20
Q

What was the cause of the Kellwasser and Hagenberg extinctions?

A

widespread anoxia

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21
Q

What lifestyle was most affected by the kellwasser extinction?

A

Benthic (seafloor organism)

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22
Q

What are some examples of fauna affected by kellwasser?

A

Reefs (stromatoporoids, tabulate and
rugose corals);
Trilobites,
Brachiopods,
Ammonoids
Graptoloids go extinct

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23
Q

Where environments did extinction occur for the Hangenberg event?

A

Marine and freshwater

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24
Q

What distinct change occurred to fish populations in the Hangenberg event?

A

Placodermi extinction allowing space for present day fish species

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25
Q

What rock type was implaced during the Variscan orogeny?

A

Granites

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26
Q

What series is the Carboniferous split into?

A

Mississippian
Pennsylvanian

27
Q

What onshore outcrops of the Carboniferous are there in the UK?

A

Midland Valley Scotland
NE and Pennines
S Wales and Devon

28
Q

What was the global position of the UK in the Mississippian?

A

Britain is found near the equator

29
Q

What are Goniatites?

A

A type of molluscs which is a key indicator of marine conditions as it acts as a biostratigraphical marker

30
Q

What are some examples of shallow marine macrofossils from the Mississippian?

A

Crinoids
Brachiopods
Lithostrontian (colonial coral)
EKvasophyllum (solitary coral)

31
Q

How can the pre-Carboniferous topography be described?

A

Block and Basin

32
Q

How does the block structure affect thickness of sediment?

A

High relief = erosional
Low relief = depositional

33
Q

What affect does underlying granite have on rocks?

A

Granite it buoyant so will “push” up overlying rocks

34
Q

What does block and basin topography control the nature of?

A

Sedimentation

35
Q

What are the characteristics of the Mississippian limestone facies?

A

Shallow marine reefs and crinoidal banks, shelly coral biostromes
Platform carbonates on flanks of landmasses

36
Q

What is the name of the end Mississippian (Namurian) facies?

A

Millstone grit facies

37
Q

How was the millstone grit produced?

A

Pulsed marine transgression making sediment more uniform
Coarse siliclastic sediments

38
Q

What occurred in the late Carboniferous?

A

Culmination of the Variscan orogeny
Creation of Pangea (UK equatorial)

39
Q

What are potential analogues for the depositional environments of the late carboniferous?

A

Large modern deltas (Ganges, Mississippi and Okavango)

40
Q

What will happen within the sequence of a delta is there is a recession?

A

Channels will cut into the rock sequence

41
Q

What is the transition of rock type from marine to deltaic/ shelf in the late Carboniferous?

A

Carbonate (marine) to Clastic

42
Q

What is the Yoredale?

A

Sedimentary cycle of the mid to late Carboniferous

43
Q

What are the characteristics of the Yoredale?

A

Generally north of the Craven Fault
Essentially marine.
Coals rare. High frequency, low amplitude

44
Q

What are the characteristics of the millstone grit?

A

lower parts - deep-water turbidites,
upper parts - shallow-water,
sheet-like delta deposits,
thin coals.
Marine influence progressively rare

45
Q

What are the characteristics of the coal measures?

A

Fluvio-lacustrine, humid, water-logged depositional setting. Marine influence all but absent. Driven by autocyclic processes
(e.g. lobe or channel switching) and local tectonics

46
Q

What environment developed in the Pennsylvanian in Europe and North America and what is the problem and benefit for the UK?

A

Coal swamps
Benefit provided power for development
Negative is enhanced green house effect

47
Q

Where was Britain located globally in the Permian?

A

Britain to N of Central Pangean Mountains - influence rainfall and sediment supply

48
Q

Where are the main deposits of the Permian in the UK?

A

SW midlands and NE England

49
Q

What type of deposit is linked to the Permian?

A

New Red Sandstone

50
Q

How many stages are there in the Permian and do they link to the UK?

A

9 but largely redundant in the UK

51
Q

What occurred from the transition from the Carboniferous to the Permian?

A

From ice house to greenhouse

52
Q

How can the Permian be identified in the East UK?

A

Earlier Rotliegend (red & yellow sediments), succeeded by Zechstein (evaporites and carbonates)

53
Q

How can the base of the Permian be identified?

A

Base often identified using (rare) plant
assemblages or by dating volcanics

54
Q

How is the top of the Permian generally identified?

A

Taken below the first pebble bed in the Triassic Sherwood SST

55
Q

What processes would have dominated the end of the early Permian?

A

Aeolian deposits - creating Sabkhas (like those of modern day Qatar)

56
Q

What in the Permian acts as an important reservoir for oil and gas?

A

Early Permian SST

57
Q

What names are given to the Early to Mid Permian sequence?

A

Cisuralian (early Permian) to early
Guadalupian (mid Permian)

58
Q

What are the names given from the Mid to Late Permian sequence?

A

Late Guadalupian to Wuchaipingian
(late Permian)

59
Q

What marine transgression occurred in the late Permian?

A

Zechstein

60
Q

Why are so many faults appear to be present in the Carboniferous?

A

Due to the economic importance of coals, oils and gases in these rocks

61
Q

What economic deposit can be found in the late Permian?

A

Salt deposits

62
Q

What are the 2 stages of the zechstein?

A

First - carbonate rich shale throughout North Sea.
Succeeded by carbonate units in NE England - the Magnesian Limestone

63
Q

How do the Zechstein deposits occur in east England?

A

series of cycles, 4 main lower, 1 minor upper cycle

64
Q

What are the zechstein cycles dominated by?

A

evaporites or carbonates or a mix of detrital and evaporates

65
Q

What are the zechstein cycles underlain by?

A

Marl slate

66
Q

What might have been the 2 reasons for the termination of a zechstein cycle?

A

Flood (Highstand)
or
Drying out (Evaporites/hypersaline phase)