The Geology of Highgate Wood and Queen’s Wood by Diana Clements
Highgate Wood and Queen’s Wood have been designated a RIGS (Regionally Important Geological Site) by the London Geodiversity Partnership. A glance at the BGS 1:50,000 North London map may cause you to wonder why; the only rock-type mentioned is London Clay and it is adjacent to Hampstead Heath where geology is much more in evidence.
Why then was there a Romano-British pottery site on the highest point of Highgate Wood? London
Clay is not a particularly good potting clay whereas the overlying Claygate Member at the top of the London Clay Formation has provided most of the traditional yellow London Stock bricks for the 19th century housing in the area. Exposures circle Hampstead Heath and many of the brick pits are labelled on the 1920s 6 inch maps of the area. Tell-tale contorted, blackened and welded bricks in garden walls indicate brickmaking in the close vicinity; the bricks were not of sufficient quality to travel far and were made more or less where the clay was dug and stacked into large clamps for firing. The over-burnt bricks came from the centre of the clamp. The Claygate Beds are a more sandy facies than the underlying London Clay and indicate a shallowing-up sequence of alternating silt and fine-grained sand, becoming progressively sandier towards the top. It is the coarser nature of these beds that make them suitable for brickmaking and potting generally which points to the probable reason why the Romano-British pottery site is situated here.