Raygill Quarry Grid Reference [SD 940451] is in Lothersdale, North Yorkshire. The quarry exposes Embsay (Carboniferous) limestone, the mineral barytes and a view of the crest of the Lothersdale Anticline. It also demonstrates one elegant solution to reclaiming disused quarries by converting it to a Trout Fishery. This has the advantage of preserving the quarry faces for geologists to view.
The quarry has a lot to offer the geologist. In the SW corner of the quarry the complex anticlinal structure can be observed. Here the limestone is overlain conformably by a predominantly calcisiltite and mudstone bed (Hodder Mudstone) the top of the quarry face on the north side of the crest. The limestone, once thought to be Chatburn Limestone (Earp et al), is now considered to be Embsay Limestone, as Riley (1990) records the first entry of the primitive archaediscid foraminifers of the Eoparastaffella Cf4β Subzone occurs at the type locality near Skipton some 9.7 m above the base of the member. This indicates that the limestone spans late Chadian to early Arundian. Other highlights to be seen in Raygill Delf include evidence of barytes mining and a sequence of fissures which have been excavated for mammalian remains.
Grid Reference [SD 940451]
The tectonic structures of the district are of two ages: those formed during late Palaeozoic times (Hercynian) and those formed in post-Triassic times (Alpine). The local effects of the Hercynian orogeny are large-scale complex compressional structures of which the Ribblesdale Fold Belt is a classic example. Here in the Craven Basin a complex series of anticlines and synclines which trend WSW - ENE can be seen. The Lothersdale Anticline is one of the main components of the Ribblesdale Fold Belt.
The outcrop of the axis of the Lothersdale anticline passes through the SW corner of Raygill Quarry (and Dowshaw Delf nearby which incidently is very much overgrown). The core appears to be faulted with minor folding running through the outcrop. The limestone is seen to be dipping between 20o and 90o. The trend of the anticline is consistent with the trend WSW - NEN of the Ribblesdale Fold Belt.
Grid Reference [SD 940451].
The dominating outcrop of Embsay Limestone represents the flank of the Lothersdale Anticline. This deposit is sourced from the Central Lancashire High (CLH) and is of Arundian age.
The limestones are ooliths produced in a turbidite-fronted sequence on the southern edge of the basin.
Grid Reference [SD 941452].
In 1880, on the south side of Raygill Delf, a fissure was excavated and mammalian bones and teeth were found. The fissures (as shown in the photograph to the right) are Ice Age potholes and are between 2 to 5 metres wide. The mammalian fissure is commonly known as the Hippopotamus Bone Bed and was overlain by boulder clay. Earp et al suggests the origin of the deposits to be part of an interglacial phase (Saale - Weichsel of N. Germany). L.C. Miall (1880) and J.W. Davis (1881 and 1887) first described the fissures and gave the following faunal list:
Elephas antiquus, Rhinoceras leptorhinus, Cervus capreolus, Felis leo var. spelaea, Bear, Bison, Hyaena, Hippopotamus, Roebuck.
The specimens were placed in the Leeds City Museum and unfortunately were subjected to bombing during the war. Subsequently however, Dr. D.E. Owens has confirmed the identification of R. leptorhinus, F. leo var. spelaea, Hippopotamus and Hippopotamus.
Grid Reference [SD 941452].
In Raygill Delf there are numerous mineral veins located along the many faults. Their thickness varies from 10cm to about 2m. The two most common minerals are calcite and barytes and it is the barytes that was first mined as early as 1876. The northern east-west vein or Main Vein, is the one that has been extensively worked. Other minerals found include fluorite and dialogite ( a carbonate of manganese).
The mine closed in 1895 since when only a small quantity of barytes has been produced during the limestone quarrying. Between 1876 and 1895 Raygill produced 35 000 tons of barytes.
Barytes (Barites) is a sulphate of Barium (BaSO4). It belongs in the orthorhombic crystal system. The crystals are usually tabular; it also found as globular concretions as shown in the photo to the right. It is colourless to white, often yellow, blue, green, red, or brown (colours as a result of contained impurities of iron minerals). It can be transparent to translucent; with vitreous lustre and a streak of white. It occurs as a gangue mineral in metalliferous hydrothermal veins associated with the ores of lead, copper, zinc, silver and iron. Other gangue minerals found alongside barytes include quartz, fluorite and dolomite. It has a hardness of 3 - 3½, has a perfect basal cleavage and uneven fracture. About 20,000 tonnes of barytes is processed each year at Cavendish Mill (Peak District) and used as a lubricant in oil and gas drilling, in paint manufacture and in other industrial products.