| Harwich Formation | |
|---|---|
| Stratigraphic range: Ypresian | |
| Type | Formation |
| Unit of | Thames Group |
| Sub-units | Swanscombe Member, Tilehurst Member, Harwich Member, Oldhaven Beds, Blackheath Member, Hales Clay |
| Underlies | London Clay Formation |
| Overlies | Lambeth Group |
| Thickness | <2-24 m |
| Lithology | |
| Primary | sand, silt & clay |
| Other | gravel |
| Location | |
| Region | southeastern England |
| Country | United Kingdom |
| Extent | London Basin |
| Type section | |
| Named for | Harwich |
The Harwich Formation is a geological formation found in the London Basin of southeastern England. It is Ypresian (early Eocene) in age. It lies unconformably on the Lambeth Group over most of its extent, but may overlie either the Thanet Formation or the Chalk Group to the south. It is overlain by the London Clay Formation.[1][2]