Craven Fault System

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The Craven Fault System is the name applied by geologists to the group of crustal faults in the Pennines [1] that form the southern edge of the Askrigg Block and which partly bounds the Craven Basin. Sections of the system's component faults which include the North, Middle and South Craven faults and the Feizor Fault [2] are evident at the surface in the form of degraded faults scarps where Carboniferous Limestone abuts millstone grit. The fault system is approximately coincident with the southwestern edge of the Yorkshire Dales National Park and the northeastern edge of the Bowland Fells.

Contents

Malham Cove cliff face may have formed as a fault scarp on the Middle Craven Fault but has since retreated ca. 600 m Malham Cove.jpg
Malham Cove cliff face may have formed as a fault scarp on the Middle Craven Fault but has since retreated ca. 600 m

Location

The Craven Faults define the north edge of the Craven Basin and the Aire Gap Map-Aire Gap England.png
The Craven Faults define the north edge of the Craven Basin and the Aire Gap

The Craven Faults are major crustal fractures across the Pennines. These faults constitute a zone crossing the backbone of England from west to east commencing near Leck, Lancashire at 54°11′26″N2°31′38″W / 54.190507°N 2.527339°W / 54.190507; -2.527339 then branching three ways:

The Craven Gap is sometimes called the Aire Gap, but to do so necessitates including the Aire Fault; that runs from the south end of the South Craven Fault: from Gargrave towards Leeds. Although of less amplitude than the three Craven faults the course of the Aire Fault is made more apparent by the River Aire. The broad Aire Gap separates the Yorkshire Dales from the Bowland Fells and the Millstone Grit plateaux of the South Pennines. [5]

Geological age

The strata along the River Twiss, Ingleton, below Quaternary terminal moraine at Raven Ray Ingleton WTL.svg
The strata along the River Twiss, Ingleton, below Quaternary terminal moraine at Raven Ray

The fault system comprises the North Craven Fault, Middle Craven Fault, South Craven Fault and Feizor Fault along with various other unnamed faults. The Middle Craven Fault moved mainly during Carboniferous times and marks the southern limit of the Askrigg Block. However the North and South Craven faults continued to be active into post-Triassic times. [4] :16 The Great Scar Limestone is exposed north of the Middle Craven Fault at Malham Cove and at Gordale Scar [5] and along the South Craven Fault at Giggleswick Scar.

Erosion

A. Upthrown fault block; B. Downthrown fault block; 1. Fault zone; 2. Steep face; 3. Gentle slope; 4. Valley filled with eroded surface runoff; 5. Sedimentary rock layers; 6. Bedrock; 7. Sedimentary rock layers worn away; these matched layers 5. Thrown fault blocks.jpg
A. Upthrown fault block; B. Downthrown fault block; 1. Fault zone; 2. Steep face; 3. Gentle slope; 4. Valley filled with eroded surface runoff; 5. Sedimentary rock layers; 6. Bedrock; 7. Sedimentary rock layers worn away; these matched layers 5.
Here the central hill is of sandstone whereas that on the right is of limestone. On the fault line^ - geograph.org.uk - 1175269.jpg
Here the central hill is of sandstone whereas that on the right is of limestone.

The Great Scar Limestone is over 200 metres thick and the overlying Yoredale Series was over 300 metres thick before weathering. [7] :12 The vertical throw of the fault zone is up to 1,800 m (5,906 ft).

Near Ingleton, North Yorkshire the North Craven Fault has a downthrow of about 200 metres (660 ft), and a few hundred yards away the South Craven Fault has a downthrow of about 1,200 metres (3,900 ft). [8] The fault plane of the North Craven Fault is exposed in Swilla Glen. [9]

Charles Darwin used the Craven Fault to illustrate how nature can so well conceal dramatic events: "The Craven Fault, for instance, extends for upwards of 30 miles, and along this line the vertical displacement of strata has varied from 600 to 3000 feet." [10]

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White Scar Caves cave in United Kingdom

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River Twiss river in the United Kingdom

The River Twiss is a river in the county of Yorkshire, England. The source of the river is Kingsdale Beck which rises at Kingsdale Head at the confluence of Back Gill and Long Gill in the Yorkshire Dales. Beneath Keld Head, it changes its name to the River Twiss. It has two notable waterfalls, Thornton Force and Pecca Falls, and its course follows part of the Ingleton Waterfalls Walk, then through Swilla Glen to Thornton in Lonsdale and down to Ingleton, where it meets the River Doe to form the River Greta.

Ingleton Waterfalls Trail

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Mountains and hills of England

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South Pennines

The South Pennines is a region of moorland and hill country in northern England lying towards the southern end of the Pennines. In the west it includes the Rossendale Valley and the West Pennine Moors. It is bounded by the Greater Manchester conurbation in the west and the Bowland Fells and Yorkshire Dales to the north. To the east it is fringed by the towns of West Yorkshire whilst to the south it is bounded by the Peak District. The rural South Pennine Moors constitutes both a Site of Special Scientific Interest and Special Area of Conservation.

Geology of Yorkshire

The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages. The strata become gradually younger from west to east.

The Askrigg Block is the name applied by geologists to the crustal block forming a part of the Pennines of northern England and which is essentially coincident with the Yorkshire Dales. It is defined by the Dent Fault to the west and the Craven Fault System to the south whilst to the north it is separated from the Alston Block by the Stainmore Trough. It originated as a geological structure during the Carboniferous Period as a major element in the Pennine Block & Basin Province.

Dent Fault

The Dent Fault is a major fault zone on the boundary between the counties of Cumbria and North Yorkshire in northern England. It is named after the village of Dent in Dentdale, on the western margin of the Yorkshire Dales.

Aire Gap

Aire Gap is a pass through the Pennines in England formed by geologic faults and carved out by glaciers. The term is used to describe a geological division, a travel route, or a location that is an entry into the Aire river valley.

Feizor Hamlet in North Yorkshire, England

Feizor is a hamlet in the Yorkshire Dales National Park, England. The name means "Fech's summer pasture" probably in reference to a prominent local landowner whose name was recorded at the time of the Norman conquest.

Kingsdale valley in UK

Kingsdale is a valley on the western edge of the Yorkshire Dales National Park in northern England. The name Kingsdale derives from a combination of Old Norse and Old English which means The valley where the cows were kept. Humans were active in Kingsdale from 6,700 BC onwards. Evidence of fire-pits used by hunter-gatherers have been found in the dale.

The geology of Lancashire in northwest England consists in the main of Carboniferous age rocks but with Triassic sandstones and mudstones at or near the surface of the lowlands bordering the Irish Sea though these are largely obscured by Quaternary deposits.

The Craven Basin is a sedimentary basin in northern England, having the shape of a southerly-tilted graben which was active during the Carboniferous period. It is one of a series of such basins which developed across northern England in this period separating upstanding blocks which were typically underlain by buoyant granites. The basin trends roughly east–west and is bounded by the Lake District block to the northwest, the Askrigg Block to the northeast and the Central Lancashire High to the south. One distinct section of the basin is a half graben which contains over 3km thickness of late Devonian to Courceyan strata and is referred to as the Bowland Sub-basin. These basins resulted from the crust of the region being subjected to a north–south lateral tension regime which began in the late Devonian and lasted through until the Visean.

References

  1. ↑ Aitkenhead, N. et al 2002 British Regional geology: the Pennines and adjacent areas (4th Edn) British Geological Survey, Nottingham
  2. ↑ British Geological Survey 1:50,000 scale geological map (England and Wales) sheet 60 Settle
  3. ↑ British Geological Survey, Geology of England and IOM, DiGMapGB625, data NERC 2008
  4. 1 2 Wilson, Alfred (1992). Geology of the Yorkshire Dales National Park. Grassington: Yorkshire Dales National Park Committee. p. 2. ISBN   0-905455-34-7.
  5. 1 2 Donkin, Kevin (2006). Circular Walks Along the Pennine Way. London: Frances Lincoln Ltd. ISBN   978-0-7112-2665-4.
  6. ↑ CPGS 2003, p. 8.
  7. ↑ Kelsall, Dennis; Kelsall, Jan (2008). The Yorkshire Dales: South and West. Milnthorpe: Cicerone. ISBN   978-1-85284-485-1.
  8. ↑ Waltham 2007, pp. 54–57.
  9. ↑ Waltham 2007, p. 91.
  10. ↑ Darwin, Charles. "On the Imperfection of the Geological Record" [XIV]. On the Origin of Species.

Bibliography

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