Try: BGS geology viewer Open viewer zoom in and at 1:50 000 a key appears. You may need to adjust the transparancy of the overlay to accurately match the key. This indicates surface geology to be London Clay over the vast majority (there are no overlying / superficial deposits indicated). To the north towards Bellenden Rd area the geology changes to Lambeth Group clay/silt/sand aka Woolwich & Reading beds, believe this is also known as brick earth; the combination of clay and sand being fundamental to brick manufacture (I think)
