 Crinoid fossils caked in a rock-solid pastry. |
Over the next 40 million years: Top up and drain off excess water several times. Add new ingredients as they evolve. Our sea-levels rise and fall repeatedly through the ages. Fresh ingredients come and go. The motion of the swilling seas helps seabed sand and mud ('sediment') to settle over their old bodies. As the years pass the bitty sediment hardens under pressure into a rock-solid pastry, preserving the remains beneath the sea-bed. The pastry is made up of Hornton Stone (ironstone) and Blue Lias (clay and limestone). |
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