A geotrail
guide giving more information about the Cleveland Dyke at Cliff Rigg
Quarry, Great Ayton, North Yorkshire can be downloaded by clicking on
the website below:
http://tvrigs.org.uk/wp-content/uploads/2008/03/cliff-rigg-final.pdf
(You will need
adobe acrobat reader which you can download HERE)
if you wish to print the geotrail.
This period
began with another major lowering of sea-level together with uplift,
and nearly all of Britain, apart from the south-east emerged as land.
Because of this, it is most likely that no Tertiary sediments were
deposited in Northern England, although thick sequences are known
offshore beneath the North sea.
The western
side of the British Isles was affected by the opening of the North
Atlantic since, by the early Tertiary, the spreading North
Atlantic ridge had developed far enough north to begin splitting
Northern Europe from Greenland. Separation of Greenland
from Western Scotland and Ireland was preceded by igneous
activity, viz. volcanic eruptions and the intrusion of dykes, e.g. in
Skye, Mull, Staffa (Fingal's Cave) and Northern Ireland (the Giant's Causeway).
Uplift and the
development of the constructive plate margin on the western side of
the British Isles were responsible for the general tilting of Britain
towards the south-east as well as the renewed activation of major
faults, e.g. those surrounding the Alston Block.
The
rising western and northern areas of Britain consequently underwent a
great deal of erosion thus exposing much older rocks below, while
progressively younger rocks crop out as one travels south-east. It is
believed that it was Tertiary earth movements which raised the Lake
District area into a dome from which thousands of metres of rocks
were eroded away to reveal the underlying Palaeozoic rocks.
It was during
this period of separation resulting in crustal tension that a number
of linear igneous rocks known as dykes, e.g. the Cleveland, Tynemouth
and Acklington Dykes composed of a type of basalt, were
intruded. These are the only tertiary rocks to be seen in Northern
England. The Cleveland Dyke and the sites where it was quarried for
roadstone can be seen in several places, e.g. at Great Ayton, and at
Castleton. In fact, from the the vantage point of Roseberry Topping
the dyke, being a more resistant rock, can be seen to form a distinct
ridge running in a WNW-ESE direction.
A general trend
in global cooling began during the Tertiary, and this was to
culminate in the sequence of cold and temperate climates which have
affected Britain in the last 2 million years.
