Rare 55-million-year-old fossil discovered in Carshalton

EXCLUSIVE This incredible find reveals the small creatures fossilised beneath our feet — water dwellers that lived here millions of years ago. Carshalton’s oldest residents, if you like. The area on the corner of Butter Hill and Mill Lane was once an oyster bed, at a time when, incredibly, parts of Carshalton were submerged beneath the sea. The specimen shows oyster shells and water snails cemented together.

Ken Cole, who retired as a local councillor in 1990, has loved fossils since the age of nine. He came into possession of this beautiful reminder of Carshalton’s geological history as a child, when it was given to him by a neighbour who worked at the site where it was discovered.

Here he recounts for us how he came by it..

It was a routine day early in March 1968 at Sutton Council’s Technical Services offices in Denmark Road. A call comes in from a concerned contractor recently hired to dig drainage ditches in advance of the construction of a three story office block on the Vinyls site in Mill Lane.

Mike Hampson, former Director of Technical Services at the Council, described to me what happened next back in 1990. “It was expected to be a routine job, removing sand, clay and gravel with an excavator. However, the contractor (Token Construction Co) had hit solid rock which totally changed the nature of the work”.

The contractor had hit an unknown layer of rock in what today is known by geologists as the Lambeth Group (until recently, the Woolwich & Reading Beds). This is a series of clays and sands, about 10M thick dating from about 55 million years ago.

Carshalton then would have been about 12 degrees further south and would have been a warm, low-lying coastal plain, comprising a lagoonal and estuarine delta system.

Suddenly, Mill Lane was a centre of national attention. Both the Carshalton Times and Advertiser ran stories on it on 2nd and 14th March 1968 respectively. They reported that an expert, Dr F Cox, visited from what is now the British Geological Survey to assess the find, as did lots of amateur enthusiasts keen to get a piece of the excavated bedrock.

So what is the Lambeth Group? it is a series of clays and sands sandwiched between the Chalk and London Clay. This band follows roughly along the A232 to Croydon.

It is where these two meet that create springs, which provide the source of the River Wandle today. The mystery layer of rock is where freshwater shells in small lakes have cemented together to form what is now bands of hard limestone.

They are found in several places across South and South East London and are one of the reasons why the Jubilee Line extension didn’t happen until the late 20th Century as their presence caused insurmountable barriers for earlier tunnellers.

Apparently, the same band of rock was encountered in the early 1970s when the construction of the Westcroft Leisure Centre was started according to the Council’s Local Studies department.

No surface evidence remains of this discovery now. The Vinyl Office Block has since been demolished and replaced with flats.

Records from Sutton Council and the Geological Survey no longer exist and few people will remember the discovery, although it would be interesting to see whether any reader has a sample of the excavated limestone or indeed memories from 1968.

With thanks to Ken for writing and submitting this article