Geology of Britain overview

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Geology of Great Britain
Precambrian
Southern Britain was mainly volcanoes (edge of Godwana) and Northern Britain was on
Laurentian plate. Britain was separated by a wide ocean (Iapetus oceon)
Example Lewisian complex found in an outcrop in the northwestern part of Scotland
Cambrian
In the early Cambrian period the volcanoes and mountains of England and Wales were
eroded as the land became flooded by a rise in sea level, and new layers of sediment
were laid down. The first animals with hard shells evolved at this time, consequently,
fossils become much more common in rocks formed during this and later periods.
Iapetus Ocean opens by crustal extension (shown by lack of andesitic volcanicity in any
of the marine sequences) creates a shallow marine environment
Example Sandstones were deposited in the north of Scotland
Ordovician
Iapetus ocean closing, Balticia merged with Avalonia at the end of the Ordovician.
Ordovician had lots of volcanoes, due to the closing of the Iapetus Ocean, the vast
quantities of ash, lava and debris sometimes created island arcs.
Example volcanic ash still found in the Lake District
Silurian
Volcanism was rare (only occurring on either Pembrokeshire; instead, deposition took
place and continued into the early part of the Silurian period, with mudstones and
sandstones being laid down, notably in Wales. In the end of the Silurian the southern
and northern halves of Great Britain join together.
Example Volcanic ashes and lavas deposited during the Silurian are still found in the
Mendip Hills and in Pembrokeshire.

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Caledonian Orogeny
Period of mountain building caused by the closure of Iapetus Ocean, all the Iapetus crust
was crust was subducted and destroyed at this time. Sedimentation and volcanism
resulted from the two plates moving together. During the Caledonian Orogeny, fold
mountain of Himalayan proportions were formed over Scotland and the Northwest
Britain. Many rocks in Scotland were metamorphosed such as high grade regional
metamorphism in Scotland (gneiss, migmatites).…read more

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Variscan Orogeny
The closing of the Rheic Ocean at the end of the Carboniferous had a big effect on
Britain, but mainly effected Devonian and Carboniferous rocks. Fold Mountains were
produced by collisions of Laurasia and Godwana in America and Africa, but none in
Britain. There were folds produced which had tight, vertical, even and overturned folds
with an EW trend (with slate grade metamorphism over the southwest of England) NO
FOLD MOUNTAINS FORMED.…read more

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The modern continents having formed, the Cretaceous saw the formation of the Atlantic
Ocean, gradually separating northern Scotland from North America. The land
underwent a series of uplifts to form a fertile plain.
the seas started to flood the land again until much of Great Britain were again below the
sea, there were lake and river deposits throughout England, very wet > lots of chalk
Example the white cliffs of Dover
KT Boundary
75% of death *(bye, bye dinosaurs) Meteor impact and volcanoes.…read more

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