GLA 14: Gilbert’s Pit, Charlton SSSI

GLA 14: Gilbert’s Pit, Charlton SSSI
Royal Borough of Greenwich, TQ 418 786
Ownership: Local Authority

Gilbert’s Pit was one of a number in the Charlton area and a nearby pit now contains the football stadium for Charlton Athletic. Gilbert’s Pit holds SSSI status as it is the type section of the Woolwich Beds, part of the Early Eocene Lambeth Group. Quarrying operations in Gilbert’s Pit ceased in 1938 but when quarried it displayed the full succession from the top of the Chalk, through the Thanet Formation (a very pure Paleocene sand) and the variable Lambeth Group to the Blackheath pebble beds at the top. The main quarrying interests were Chalk for lime and Thanet Sand for use in the foundries of the adjacent Woolwich Arsenal and glass for making bottles. A full description and further reading can be found in GA Guide 68, pp. 85-94.

The Thanet Sand Formation and Upnor Formation are now covered by scree as shown in the section diagram, and the Late Cretaceous White Chalk below is now completely buried by 10m of wartime bomb damage rubble.

All that can now be seen of the former workings is the top of the section. The rest is covered by scree. Nevertheless it is the finest and scientifically most important pre-London Clay Palaeogene site in the London area*. For this reason it has been designated an SSSI. It gives engineers and geologists a rare view of these sediments that underlie London, helping them understand some of the difficulties they may encounter when working through the Lambeth Group, notorious for its changing and ‘unexpected’ lithology, for the many building and tunnelling projects in London. It is for this reason that is designated a Site of Special Scientific Interest.

gla14

Blackheath Beds at top of eastern
face. Photo: Laurie Baker

Information sign in front of slumped material. Source: London’s Foundations, page 143

The variable Lambeth Group displays a variety of lithologies. The sands and fossiliferous shelly clays of the Woolwich Formation, named after this area. Occasional shells can be found at the bottom of the slope where they have rolled down. This sequence is evidence of a transition from marine conditions to mud flats similar to modern mangrove swamps and lagoons, with varying amounts of fresh water. The Blackheath Beds are the highest, and therefore youngest, part of the sequence seen in the pit. They are composed of black well-rounded pebbles of flint in a sandy matrix with occasional seams of shells and were deposited in marine channels that were cut into the underlying Woolwich Beds. Some pebbles have rolled down the slope and piled up behind the fence.

In winter, when the trees are bare, on the steep face on the south side of the old quarry, alternating layers of clay and sand can often be seen more clearly than on the east face. The exposure extends down through the Blackheath Beds, Woolwich Formation to expose the top of the Upnor Formation, and on rare occasions, even the Thanet Sand.

Access
The nearest station is at Charlton, which is a 10-minute walk from Gilbert’s Pit. There are six trains an hour from London Bridge (four of them from Charing Cross and Waterloo East). Walk along Floyd Road/Charlton Lane to entrance near level crossing. The nearest underground station is North Greenwich (Jubilee Line), thence by one of three bus routes: 161. 188 or 472 (alight at Eastmoor Street bus stop). Route 380 travels along Thorntree Road. Parking is available in Thorntree Road. To gain access to the sections Greenwich Parks & Open Spaces must be contacted on 020 8921 2937 or parks@royalgreenwich.gov.uk. The South-east London Green Chain Walk (http://greenchain.com/downloads/file/1/green_chain_geo_trail_guide) goes through Gilbert’s Pit and the Capital Ring passes through Maryon Park nearby.

*Daley, B. & Balson, P.S. 1999: British Tertiary Stratigraphy. Geological Conservation Review Series No. 15, Joint Nature Conservation Committee, Peterborough, pp. 56-59

Site Map OS Topography © Crown Copyright
Source: London’s foundations, page 142

gla14 map

 

 

 

 

Click here to return to the site list

Click here to download the complete Guide to Important Geological sites in London