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Earth history and life - 29202 > Lower Palaeozoic of the British Isles > Flashcards

Lower Palaeozoic of the British Isles Flashcards

1
Q

What periods are encompassed by the lower Palaeozoic?

A

Cambrian
Ordovician
Silurian

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2
Q

What occurred in the UK in the Lower Palaeozoic?

A

Increased influence of volcanoes on UK stratigraphy
Increased diversity of the fossil record

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3
Q

What occurs in terms of continents in the lower Palaeozoic?

A

Microcontinent Avalonia breaks from Gowanda starting the closure of the lapetus ocean bringing together the N and S of the UK

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4
Q

What does a regression in sea level to do temperature?

A

Causes a temperature increase as more land exposed

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5
Q

What transgression and regression occurred in the lower Palaeozoic? (young to old)

A

End Silurian regression
Late Ordovician cooling
Cambrian transgression

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6
Q

What parts of the UK have Cambrian age rocks?

A

Northwest Highlands
Wrekin
Nuneaton
Pembrokeshire
Harlech Dome

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7
Q

How can mapping show areas which were previously connected?

A

Overlaps, gaps and continental shelf areas can be mapped (i.e. The Niger delta overlaps with south America and gaps between west North America and Northeast Africa)

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8
Q

Why cant coastline fit and palaeomagnetism be used for Lower Palaeozoic rocks?

A

As they have undergone multiple orogonies and seafloor can only be used to date 200 Mya

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9
Q

How are palaeogeographic maps constructed in ‘deep’ time in the absence of fit or palaeomagnetic stripes?

A

Fossil records i.e. Olenellus in the Northwest Highlands and Olenus In Pembrokeshire

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10
Q

What did Cocks and Fortey identify?

A

equatorial and higher latitude realms across Iapetus and also two faunal realms at temperate and high latitudes

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11
Q

What species did Cocks and Fortey identify in equatorial regions of the palaeozoic?

A

endemic bathyrid trilobites
finkelnburgiid brachiopods
leperditiid ostracods

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12
Q

What species did Cocks and Fortey identify in high latitude regions of the palaeozoic?

A

megalaspid trilobites
lycophoriid brachiopod
calymenacean trilobites
gondwanan inarticulates

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13
Q

What stratigraphy links to the Cambrian transgression shown in NW Highlands?

A

The Eriboll which overlies the Torridon Group with a Lewisian Gneiss base

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14
Q

What did the Moine thrust do to the stratigraphy of the NW Highlands?

A

Made Pre-Cambrian Overlie cambrian (Moine Schist)

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15
Q

Where can Ordovician outcrops be located in the UK?

A

Girvan (Ballantrae volcanic group)
Moffat
Pembrokeshire

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16
Q

What are the fossil fauna of the Ordovician like in the UK?

A

Exclusively marine

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17
Q

What are some examples of Ordovician fossils located in the UK?

A

Coral
Brachiopod
Ostracods
Graptolites
Trilobite
Conodonts

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18
Q

What were the dominant features of the Ordovician paleogeography? (middle Ordovician)

A

Gondwana supercontinent
Paleo-Tethys ocean
Iapetus ocean
Micro-continents (Baltica, Laurentia)

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19
Q

What were the continents of the early Ordovician?

A

Equatorial - Laurentia and Siberia
Higher latitude - Gondwana, Baltica and Avalonia

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20
Q

What is the Ballanytrae Volcanic Group (BVG) composed of?

A

pillow lavas (deep marine)
black shales (with graptolites)
Cherts (silica)
Spillites (Basalt and Na rich plagioclase)

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21
Q

What is the age of BVG?

A

Early to Mid-Ordovician

22
Q

What is the BVG considered to be?

A

Fragment of ophiolite complex

23
Q

What happened to the BVG after formation?

A

It was eroded and faulted creating an irregular topography with impure limestones on topographic highs and coarse clastics

24
Q

What process is responsible in part for the production of ophiolites?

A

Obduction (sedimentation occurs on the scraped material of the oceanic plate)

25
Q

What is Bentonite?

A

Clay formed from weathering of feldspars
Volcanic ash horizons

26
Q

What is the chronology of the Silurian?

A

444 Ma to 416 Ma

27
Q

What geographical events occurred within the Silurian?

A

Final closure of Iapetus Ocean
Caledonian Orogeny

28
Q

What is the Silurian stratigraphy like in the Welsh basin and the Midlands?

A

Welsh basin - deep-water
Midlands- Sub-tropical reefs

29
Q

What is the Silurian Biotas like in general?

A

Marine while showing traces of initial land colonisation

30
Q

What are some examples of Silurian biota?

A

Crinoids
Trilobites
Rugose corals
Tabulate corals
Bryozoa
Graptolites
Cooksonia (early land plant)

31
Q

What are the 4 epochs of the Silurian?

A

Přídolí
Ludlow
Wenlock
Llandovery

32
Q

What event Silurian occurred in Přídolí
in the welsh basin?

A

Bone bed

33
Q

What event Silurian occurred in Ludlow
in the welsh basin?

A

Deepening and shallowing of the basin

34
Q

What event Silurian occurred in Wenlock
in the welsh basin?

A

Deepening and shallowing of basin

35
Q

What event Silurian occurred in Llandovery
in the welsh basin?

A

Submergence

36
Q

What is an orogenic event?

A

Ocean basin closure and continental collision creates new mountain range

37
Q

What is mountain building from an orogeny followed by?

A

Erosion and regional unconformities

38
Q

What orogonies occurred to the British Isles during the Phanerozoic?

A

Alpine orogeny (Aplides)
Variscan orogeny (Variscides)
Caledonian orogeny (Caledonides)

39
Q

What is the age of rock for the Alpine orogeny?

A

Mesozoic-Cenozoic

40
Q

What is the age of rock for the Variscan orogeny?

A

Mid-Late Palaeozoic

41
Q

What is the age of rock for the Caledonian orogeny?

A

Early Palaeozoic

42
Q

What is the cause of the Alpine orogeny?

A

Closing of the Tethys ocean

43
Q

What is the cause of the Variscan orogeny?

A

Rheic ocean closure

44
Q

What is the cause of the Caledonian orogeny?

A

Iapetus ocean closure

45
Q

What was the cause of the Grampian mountains within the British isles?

A

Main phase of the Caledonian orogeny

46
Q

How did the tectonic framework change between Laurentia and Avalonia?

A

Late Cambrian - early Ordo = subduction at Lauren
Mid-Ordo = subduction at Lauren and Ava
Late-Ordo to early Silurian = subduct at Lauren
Mid to late Silurian = Orogenic as Ava and Lauren contact

47
Q

Where did the Iapetus suture occur in the British Isles?

A

At boundary between Avalonia and Laurentia (around Scottish border)

48
Q

When did the final phase of the Caledonian Orogeny take place?

A

In the Devonian

49
Q

What deformation phase and formation is the final phase of the Caledonian orogeny?

A

Acadian phase of deformation
Laurussia formation

50
Q

What is much of the volcanism in the late Silurian and Devonian associated with?

A

Caledonian orogeny

51
Q

What are the Younger Granites?

A

Significant granitic intrusions in Scotland and North England

Earth history and life - 29202 (29 decks)

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