Alum Bay (part of Headon Warren and West High Down SSSI)
Location and Access Information
Grid Reference: SZ 316852
Cliff exposure of Eocene sands in Alum Bay.
Alum Bay is located at the far western tip of the Isle of Wight. Access to the cliff top and the large car park at the Needles Pleasure Park is gained by the B3322 from Totland. There are a series of steps down the cliff or a chair lift from the Pleasure Park.
View the site map on Nature on the Map
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Geological Interest
The coastal section from Alum Bay to Totland Bay on the west coast of the Isle of Wight is one of the most well-known geological localities in Britain and has been studied by geologists for over 170 years. Within the site, the vertically inclined beds of rock provide a complete sequence from the Upper Cretaceous (142-65 million years ago) Chalk to the Bembridge Limestone of Oligocene age (30 million years old), and contain important fossil mammals, reptiles and floras.
The rock sequence provides a complete section from the Reading Clay, which rests unconformably upon the Chalk, up through the Oldhaven Formation, London Clay, Bracklesham Group, Barton Clay, Barton Sand, Headon Hill Formation and into the Bembridge Limestone Formation. Study of these sediments reveals the continually changing sequence of environments which existed in the western Isle of Wight during Eocene times, and significant environmental differences between this section and sections of similar age at Whitecliff Bay and Hordle can be recognised. The famous coloured sands of Alum Bay are largely found within the outcrop of the Bracklesham Group in the central part of Alum Bay.
