The Craven Basin is a

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...

in northern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

, having the shape of a southerly-tilted

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

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

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...

s. The basin trends roughly east–west and is bounded by the Lake District block to the northwest, the

Askrigg Block 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 ...

to the northeast and the Central Lancashire High to the south. One distinct section of the basin is a

half graben A half-graben is a geological structure bounded by a fault along one side of its boundaries, unlike a full graben where a depressed block of land is bordered by parallel faults. Rift and fault structure A rift is a region where the lithosphere ...

which contains over 3km thickness of late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...

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.

Fill

The proven sedimentary fill in the Craven Basin starts with Courceyan age mudstones and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

s of the Chatburn Limestone Group, followed by the similar sediments deposited from Chadian to Asbian times and assigned to the Worston Shale Group. The basal part of this group is the Clitheroe Limestone which is

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the Hodder Mudstone. Completing the group are the Hodderense Limestone and Pendleside Limestone. The basin fill is completed by the Brigantian age Bowland Shale Group which comprises the Pendleside

Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s within what is otherwise a mudstone succession.

Craven Fault System

The boundary between the Craven Basin and the Askrigg Block is defined by the

Craven Fault System The Craven Fault System is the name applied by geologists to the group of crustal faults in the Pennines that form the southern edge of the Askrigg Block and which partly bounds the Craven Basin. Sections of the system's component faults whic ...

which comprises the North, Middle and South Craven faults. The last-named actually extends into the basin. There is a reef belt which runs along the line of the Middle Craven Fault between

Settle Settle or SETTLE may refer to: Places * Settle, Kentucky, United States * Settle, North Yorkshire, a town in England ** Settle Rural District, a historical administrative district Music * Settle (band), an indie rock band from Pennsylvania * ''S ...

and

Cracoe Cracoe is a small village and civil parish in the Craven district of North Yorkshire, England. It is situated near to Rylstone and about 6 miles south-west of Grassington. Cracoe has an estimated population of 160 residents, measured at 17 ...

References

{{Reflist Geology of England Sedimentary basins of Europe Paleozoic rifts and grabens