Fyfield Down (SSSI)
Location and Access Information
Grid Reference: SU 136709
Sarsen stones at Fyfield Down
Fyfield Down National Nature Reserve (NNR) is located 5km to the west of Marlborough. The site can be accessed by foot from a number of points, but is probably best approached from the small car park at Grid Reference SU 159699 (just off the A4). From the car park a marked path and sign posted way leads to the NNR and the valley bottom.
Further information on the NNR can be obtained from the Fyfield Down NNR page.
View the site map on Nature on the Map
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Geological Interest
Fyfield Down is a high plateau of chalk downland dissected by a system of dry valleys which contain one of the highest concentrations of sarsen stones in Britain. Trains (long lines) of the stones occur, lying in the position that they were transported to by processes of freezing and thawing of the ground during the Ice Age. Sarsen stones are the isolated remnant blocks of weathered Tertiary sandstone, probably from within the Reading Formation and indicate that these Tertiary sediments formerly extended well beyond their present outcrop.
Cementation of the sands probably occurred just below the ground surface under an arid or semi-arid climate, perhaps 5-10 million years ago, and the surrounding uncemented sediments have long since been washed away. The sarsens have been used in the construction of the nearby monument of Avebury. The stones also represent one of the most substantial natural exposures of hard rock in lowland Britain and provide a substrate for the growth of a diverse relict lichen flora of considerable note. Some lichens are typical of highland Britain and are rare in the lowlands while others are characteristic of rocky sea coasts.
