Griff Hill Quarry

Also within

Warwickshire County

Condition (Natural England)

Geology & landscape

Mining / Industrial: Quarry · Geological Period: Cambrian, Carboniferous, Ordovician, Triassic

Landscape processes: Volcanic / Igneous

Description

Description Griff Hill Quarry is an active quarry located one kilometre north of Bedworth. The site boundary encompasses the working faces and an area of proposed quarry extension which is of key importance to facilitate further study at the site. Griff Hill Quarry exposes a complex and unique igneous sequence present in a sill 20 to 30 metres thick. The sill, of Ordovician age, is mostly of camptonite and syenite, but shows a black ultramafic cumulate facies of kaersutite – pyroxenite in the lower part of the sill. The sill dips at about 20 degrees to the southwest and the site shows a cross section through these variations. Many features are present which provide evidence towards understanding the nature of theintrusion, such as enclaves of ultramafic rock within the camptonites and late stage pink segregation veins of analcime syenite. The rocks are beautifully fresh and the transitions from ultramafic to basic to intermediate varieties are well displayed in the quarry, as well as under the microscope. The origin of the different igneous rock types is not yet fully understood, with scientific opinion divided as to whether the various facies represent a differentiation sequence or a multiple intrusion. Further research is needed to resolve this question. The sill intrudes Cambrian Stockingford Shales, which close to the sill are contact metamorphosed to cordierite and alusite hornfels. Rafts of the shales are found within the sill. The sill has been unroofed by erosion and regionally important small remnants of Carboniferous Coal Measures are preserved in fossil channel deposits. These deposits have been planed off by Triassic red marls, which lie unconformably over the bulk of the sill.