Cumnor

Also within

Oxfordshire County

Condition (Natural England)

Geology & landscape

Geological Period: Jurassic

Description

Area, 0.2 hectares 0.5 ac Description This Late Jurassic locality exposes an attenuated Corallian succession spanning the complex Lower and Middle Oxfordian cordatum tenuiserratum Zone time interval. The sequence exposes the Lower Calcareous Grit and the Natica Band, which are overlain non sequentially by the Osmington Oolite including the Pebble Bed, Third Trigonia Bed and Coral Rag. This site is remarkable for the absence of any part of the Highworth Formation and consequently shows the greatest observed attenuation of that formation Lower Trigonia Bed Highworth Grit anywhere in south west Oxfordshire. The locality is also of key palaeogeographic value as one of the few remaining outcrops in the tenuiserratum Zone Coral Rag of the Cumnor Reef. A rich ammonite fauna has been collected here, especially from the Natica Band and condensed Pebble Bed. A total of seven ammonite species of the genera Perisphinctes, Aspidoceras, Goliathiceras and Cardioceras have been recorded here including the Middle Oxfordian zonal index Cardioceras densiplicatum and the holotypes of Perisphinctes cumnorensis and Goliathiceras titan. This is an outstanding site demonstrating the complex biostratigraphy and palaeogeography of the Oxfordshire Corallian.