Abstract
X-ray analyses of Kimmeridgian clays recovered from the Warlingham Number 1 Borehole indicate that illite and kaolinite are the dominant clay minerals present. Illite, chlorite, and kaolinite, are present in the Devonian clays recovered from the Willesden Number 1 Borehole. The relationships between the clay minerals of the Kimmeridgian and Devonian clays and the clay mineral assemblage of the English Wealden is discussed.