| Lambeth Group | |
|---|---|
| Stratigraphic range: Thanetian-Ypresian | |
 Exposure in Gilbert's Pit. Dark grey clays, and light grey shelly clays of the Woolwich Formation overlying yellow-brown weathering sands of the Upnor Formation | |
| Type | Group |
| Sub-units | Upnor Formation, Reading Formation, Woolwich Formation |
| Underlies | Thames Group |
| Overlies | Thanet Sand, Chalk Group |
| Thickness | Up to 39 m |
| Lithology | |
| Primary | Clay |
| Other | Sand, Gravel, Limestone, Lignite, Sandstone, Conglomerate |
| Location | |
| Region | southern England |
| Country |  UK |
| Extent | London Basin and Hampshire Basin |
The Lambeth Group is a stratigraphic group, a set of geological rock strata in the London and Hampshire Basins of southern England. It comprises a complex of vertically and laterally varying gravels, sands, silts and clays deposited between 56-55 million years before present during the Ypresian age (lower Eocene). It is found throughout the London Basin with a thickness between 10m and 30m, and the Hampshire Basin with a thickness between 50m and less than 25m. Although this sequence only crops out in these basins, the fact that it underlies 25% of London at a depth of less than 30m means the formation is of engineering interest for tunnelling and foundations.