Key Sites - City of Oxford

This is the Oxford Geology Group gazette of  the geological Sites of Special Scientific Interest to be found within the civil administrative boundaries of Oxford City Council. 

 

Two of the three sites in the City of Oxford are accessible to the public, all year round.

 

Please consider your own and the safety of others when visiting these sites.

 

No geological hammering is allowed at these nationally important sites.  It is an offence to damage or vandalise these protected sites.

Magdalen Grove                                                                                         SP 520065

Fossiliferous sediments underlying the Summertown-Radley Terrace of the Upper Thames have been exploited by shallow workings in the north-western corner of Magdalen Grove. These form part of an important and controversial stratigraphy recognised in the deposits of this terrace, which has been claimed to provide evidence for the existence of a formerly unrecognised inter-glacial stage in the British Late Middle Pleistocene. The sediments at Magdalen Grove are richly fossiliferous, yielding mammal bones, mollusca and pollen. Although probably representing the tributary Cherwell, they have been correlated with deposits at Stanton Harcourt, in the valley of the main river. The fossil assemblage from the Eynsham Gravel indicates that it was deposited during the penultimate interglacial (correlated with Oxygen Isotope Stage 7 of the 'deep sea' record). This interglacial is a recently identified episode midway between the Hoxnian and Ipswichian Interglacials of the traditional Pleistocene record.

 

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  • The deposits at Magdalen Grove are not accessible to the public.

  • The site is owned and within the grounds of Magdalen College, Oxford.

Magdalen (Workhouse) Quarry                                                                SP 552071

The classic geological site exposes three important rock units (Beckley Sand, Shell Pebble Bed and the Wheatley Limestone) approximately 145 million years old (Upper Jurassic age). The study of the rock sequence at Magdalen Quarry has provided valuable information which has enabled geologists to partially reconstruct the geography of Upper Jurassic times, when much of the area that is now Oxfordshire was covered by a warm, shallow sea. Similar conditions to those found in the Bahama Banks today are believed to have existed at the time. Most importantly, the rock units at this site indicate the presence of a reef structure in this area, formed by growth on the sea bed of an upstanding mound of lime-secreting, marine organisms, such as corals. The proximity of the reef is indicated by the rapid changes in thickness and composition of some of the rock layers, reflecting the importance of the reef as an active source of sedimentary debris. The uppermost unit, the Wheatley limestone, represents a deposit accumulating along the northern flank of the reef. The site is therefore of major importance in the geographical reconstruction of this ancient sea. Furthermore, the presence of fossil ammonites, and more specifically Cardioceras densiplicatum, is important in enabling the deposits to be accurately placed within the Upper Jurassic rock succession.

 

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A special page about Magdalen Quarry, in our new 'Focus on...' series, will be online Spring 2015, featuring images, video, logs and sections.

  • Magdalen Quarry is accessible to the public.

  • The site is managed by Oxford City Council and a reasonable expanse of the exposure is free of vegetation. 

  • Field trip leaders should consider visiting this site in conjunction with Rock Edge Quarry, Lye Hill Quarry and Wheatley Recreation Ground.

Rock Edge Quarry (Cross Roads Quarry)                                             SP 550064

This 1.8 ha geologically important site exposes an Upper Jurassic coral-rich limestone known as the Coral Rag, believed to be approximately 145 million years old. The study of the rock sequence at Rock Edge (or Cross Roads) Quarry has provided valuable information which has enabled geologists to partially reconstruct the geography of 145 million years ago, when much of the area that is now Oxfordshire was covered by a warm, shallow sea. Similar conditions to those found in the Bahama Banks today are believed to have existed at the time. At Rock Edge the Coral Rag is rich in fossil remains, derived from corals reefs that formed in the ancient shelf sea. Close examination reveals the presence of two types of limestone, reflecting the close proximity of the reef margin. One variety consists primarily of coarse fragments broken off the reef, whilst the other is finer grained, representing the lime sand accumulating on the sea bed a short distance from the reef. Actual in situ reefs were previously visible in quarries located a few metres to the south. The study of this crucial site has helped to demonstrate the existence of the so-called Headington reef in this area during Upper Jurassic times. Rock Edge has been cited as a SSSI since 1972.

 

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A special page about Rock Edge Quarry, in our new 'Focus on...' series, will be online Spring 2015, featuring images, video, logs and sections.

  • Rock Edge Quarry is accessible to the public.

  • The site is managed by Oxford City Council and a reasonable expanse of the exposure is free of vegetation.

  • Field trip leaders should consider visiting this site in conjunction with Magdalen Quarry, Lye Hill Quarry and Wheatley Recreation Ground.