Redistribution of uranium by physical processes during weathering and implications for radon production.

Erosion of the Edale shales of Derbyshire during the Tertiary and Quaternary has resulted in sediment deposits in and on the underlying karstified limestones. Sorting during sedimentation has generated clay-rich sediments which are uranium enriched due to a clay association of uranium in the shales. Radon production in these sediments is at or close to equilibrium with their uranium content, and their fine grain-size ensures efficient radon release. Such sediments are therefore potent local sources of environmental radon.