The Craven Group is a

lithostratigraphical Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneo ...

term referring to the succession of mudstone 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 ...

rock

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...

which occur in certain parts of northern and central England and northeast Wales in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

within the Chadian to Yeadonian sub- Stages of the Carboniferous Period. Other

lithologies The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lith ...

including

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 ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

s and

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a ...

occur within the group. The Group is subdivided into numerous formations, some of which previously enjoyed group status. In

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostr ...

order (uppermost/youngest at top), these are: *Bowland Shale Formation (mudstone and siltstone) *Pendleside Limestone Formation (interbedded limestone and mudstone, conglomerate) *Hodderense Limestone Formation *Hodder Mudstone Formation (limestone and mudstone) The Craven Group unconformably overlies the Bowland High Group and elsewhere the

Clwyd Limestone Group The Clwyd Limestone Group is a stratigraphic unit (a defined sequence of rock layers) of Chadian to Brigantian age ( Lower Carboniferous) found in north Wales. It forms part of the Carboniferous Limestone Supergroup. Its most extensive outcrop ...

. It is succeeded (overlain) by the Millstone Grit GroupBritish Geological Survey 1:625,000 scale geological map ''Bedrock geology: UK South'' (5th edn) BGS, Keyworth, Notts

References

See also