Geology Site Account
Nags Head Lane M25 motorway cutting , HAROLD WOOD, London Borough of Havering, TQ572915, Historical site only
Historical information only
In 1981, during construction of the M25 motorway, a deep cutting was excavated in the London Clay and the overlying Claygate Beds just south of the point where Nags Head Lane crosses the motorway. Over a kilometre in length, the cutting exposed brown weathered clay overlying blue-grey clay containing a wealth of marine fossils such as bivalves and gastropods. Also present was the pearly nautilus – a clear indication that the seas some 50 million years ago were subtropical. More fossils were probably collected from here than from any other temporary London Clay exposure in Britain. A large collection of the fossils from this site went to the former Passmore Edwards Museum in Stratford.
Due to the need to maintain a stable slope in unstable London Clay, the shallow angle of the banks required one of the largest motorway cuttings in the country but this had the advantage of exposing a considerable area of clay for collecting. On completion of the motorway the exposure was covered with topsoil and grass but the cutting is still an impressive sight.
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Reference: Ward 1987, Ellison 2004 (p.48)
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