Hertfordshire puddingstones at The Lee. They were brought here from Mobwell near Great Missenden. Hertfordshire puddingstone is a conglomerate of flint pebbles in a silica matrix at the base of the Reading Beds, which were deposited in the Eocene (56 million years ago). The pebbles were eroded from the chalk and rounded and sorted by water action (similar to modern pebble beaches). During a brief period when the sea retreated in a semi-arid climate, capillary action brought dissolved silica from underlying rocks. The water evaporated leaving the silica which hardened around the pebbles.
Author: G Patterson