Chiltern Society PhotoGroup

Puddingstones on the north side of the Common. Puddingstone is a conglomerate of flint pebbles in a silica matrix 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