Skiddaw slate is an early
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...
metamorphosed
sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
, as first identified on the slopes of
Skiddaw
Skiddaw is a mountain in the Lake District National Park in England. Its summit is traditionally considered to be the List of Wainwrights, fourth-highest peak but depending on what topographic prominence is thought to be significant is also ...
in the
English Lake District
The Lake District, also known as ''the Lakes'' or ''Lakeland'', is a mountainous region and National parks of the United Kingdom, national park in Cumbria, North West England. It is famous for its landscape, including its lakes, coast, and mou ...
.
The base of this series is unknown. The thickness could, therefore, amount to several thousand feet of sediment. These sediments were formed about 500 mya by deposition in a shallow sea,
low-energy environment. The series contains differing grain sizes and comprises
grits
Grits (stylized as GRITS) is an American Christian hip hop group from Nashville, Tennessee. Their name is an acronym, which stands for "Grammatical Revolution In the Spirit". GRITS is made up of Stacey "Coffee" Jones and Teron "Bonafide" Carter ...
,
flag
A flag is a piece of textile, fabric (most often rectangular) with distinctive colours and design. It is used as a symbol, a signalling device, or for decoration. The term ''flag'' is also used to refer to the graphic design employed, and fla ...
s,
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...
s and
mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...
s.
In some places, there is evidence of
intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
of Skiddaw Granite into the Skiddaw Slates, close to the anticlinal axis of the Lake District.
Skiddaw slate has a grey hue (as opposed to Honister slate which has a green hue) and is used for building, in the Lake District. The traditional buildings of
Keswick and other settlements are almost entirely of Skiddaw slate. The slate is also used for making souvenirs, monuments, ornaments etc. Smaller fragments are used for gravels or for ornamental pathways.
References
Geologic formations of England
Ordovician System of Europe
Ordovician England
Lower Ordovician Series
Shale formations
Slate industry in the United Kingdom
Mining in Cumbria
Geology of Cumbria
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