Fern House Gravel Pit SSSI

Bucks County Council administration area: Wycombe District Council, Bucks County Council.

Grid reference: SU 883 885

Area of site: 1.3 ha; 3.2 acres

Access, location and parking: Access from the A4155 Marlow to Bourne End Road . Parking is at the entrance to the quarry, along the roadside. A track leads to the quarry. Permission is required from the owner.

Site description: Disused gravel pit. Slumping and vegetation growth has obscured some of the lower faces; a section has been cleared in the past to reveal a 5 m high face for study.

Geological interpretation: The SSSI notification is for the Quaternary sequence of gravels. These are the Taplow Gravel Formation and they are important for the stratigraphy and understanding of the Quaternary history of the Thames . It has yielded a number of contemporaneous fossils including a number of mammoth teeth as well as reworked Jurassic fossils (such as the robust oyster Gryphaea). The sands and gravels show a number of sedimentary structures including current bedding, pebble imbrication, ripples and solifluction deposits. The gravels are also a significant geomorphological feature of the area, forming distinct terraces. Evidence for the relative dating of the Thames Terraces is rare and this is a key site for an important and controversial period of the Quaternary (immediately post-Anglian, the Saalian Stage). Previously it was thought that the Saalian Stage was a single cold (glacial) interval between the Anglian (when the Thames was diverted by ice) and the last glacial (the Devensian) which ended 10,000 years ago. However, it is now recognised that there were a number of cold intervals. Views by Quaternary geologists vary at present and sites such as Fernhouse are crucial in providing evidence for further research.

Current and potential educational  use (geology, ecology, archaeology, industrial archaeology): No current use is intended of the site for educational groups, except for Quaternary specialists undertaking geological research. However, it has great potential for the training of geologists (at all levels) and would have appeal for geological site visits if the clear face is maintained. However, due to the importance of the site as an SSSI numerous group visits would not be appropriate.

Conservation interest: To maintain the integrity of the Taplow Gravels by preventing vegetation re-growth on the slopes.

Threats to site (present and future): Vegetation is the main threat to the gravel structure and also to access of the face. Sedimentary structures would be damaged by tree root or other root penetration. Infill would be a major threat without SSSI protection.

Constraints (basic risk assessment): Low gradient and slumped slopes make access easy and safe, although not always good exposures as the slumped material obscures the lower face. Parking and a trackway make a safe entry to the site.

Reference list/bibliography:

Bridgland, D. R. 1993. Fern House Gravel Pit. In: The Pleistocene Quaternary of the Thames . Chapman and Hall.

Bromehead, C. E. 1912. On diversions of the Bourne near Chertsey. Summary of progress, Geological Survey of Great Britain, for 1911, 74-7.

Gibbard, P. L. 1985. The Pleistocene History of the Middle Thames Valley ,     Cambridge University Press, 155 pp.

Sherlock, R. L. and Noble, A. H. 1922. The Geology of the country around Beaconsfield. Memoir of the Geological Survey of Great Britain , 59 pp.

Treacher, L. 1916. Excursion to Bourne End. Proceedings of the Geologists’    Association, 45, 107-8.

Wymer, J. J. 1968. Lower Palaeolithic Archaeology in Britain, as represented by the Thames Valley . John Baker, London , 429 pp.