Lower Palaeozoic of the British Isles Flashcards
What periods are encompassed by the lower Palaeozoic?
Cambrian
Ordovician
Silurian
What occurred in the UK in the Lower Palaeozoic?
Increased influence of volcanoes on UK stratigraphy
Increased diversity of the fossil record
What occurs in terms of continents in the lower Palaeozoic?
Microcontinent Avalonia breaks from Gowanda starting the closure of the lapetus ocean bringing together the N and S of the UK
What does a regression in sea level to do temperature?
Causes a temperature increase as more land exposed
What transgression and regression occurred in the lower Palaeozoic? (young to old)
End Silurian regression
Late Ordovician cooling
Cambrian transgression
What parts of the UK have Cambrian age rocks?
Northwest Highlands
Wrekin
Nuneaton
Pembrokeshire
Harlech Dome
How can mapping show areas which were previously connected?
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)
Why cant coastline fit and palaeomagnetism be used for Lower Palaeozoic rocks?
As they have undergone multiple orogonies and seafloor can only be used to date 200 Mya
How are palaeogeographic maps constructed in ‘deep’ time in the absence of fit or palaeomagnetic stripes?
Fossil records i.e. Olenellus in the Northwest Highlands and Olenus In Pembrokeshire
What did Cocks and Fortey identify?
equatorial and higher latitude realms across Iapetus and also two faunal realms at temperate and high latitudes
What species did Cocks and Fortey identify in equatorial regions of the palaeozoic?
endemic bathyrid trilobites
finkelnburgiid brachiopods
leperditiid ostracods
What species did Cocks and Fortey identify in high latitude regions of the palaeozoic?
megalaspid trilobites
lycophoriid brachiopod
calymenacean trilobites
gondwanan inarticulates
What stratigraphy links to the Cambrian transgression shown in NW Highlands?
The Eriboll which overlies the Torridon Group with a Lewisian Gneiss base
What did the Moine thrust do to the stratigraphy of the NW Highlands?
Made Pre-Cambrian Overlie cambrian (Moine Schist)
Where can Ordovician outcrops be located in the UK?
Girvan (Ballantrae volcanic group)
Moffat
Pembrokeshire
What are the fossil fauna of the Ordovician like in the UK?
Exclusively marine
What are some examples of Ordovician fossils located in the UK?
Coral
Brachiopod
Ostracods
Graptolites
Trilobite
Conodonts
What were the dominant features of the Ordovician paleogeography? (middle Ordovician)
Gondwana supercontinent
Paleo-Tethys ocean
Iapetus ocean
Micro-continents (Baltica, Laurentia)
What were the continents of the early Ordovician?
Equatorial - Laurentia and Siberia
Higher latitude - Gondwana, Baltica and Avalonia
What is the Ballanytrae Volcanic Group (BVG) composed of?
pillow lavas (deep marine)
black shales (with graptolites)
Cherts (silica)
Spillites (Basalt and Na rich plagioclase)