Oxford Clay

The story of the Bedfordshire brick industry began at the bottom of a relatively shallow warm sea 160 million years ago.  This is where the clay formed that is now used to make Fletton bricks.

If you examine a piece of clay you can easily see its marine origins, because it contains the fossilised remains of sea creatures.  Some are very similar to modern marine animals, other stranger fossils are those of extinct animals.

The fine Oxford Clay preserves them in exquisite detail but often their delicate shells are crushed by the weight of the clay.  Even hard bones can be crushed in this way.

Some layers of the clay contain hard limestone nodules.  In the older Lower Jurassic clays nodules often contain uncrushed fossils.  This unfortunately is rarely the case in the Oxford Clay.  The clay also contains shell beds.  These formed when sediment was only falling slowly to the sea bed and large numbers of shells, especially Gryphaea could grow undisturbed.  These beds often contain the golden coloured mineral iron pyrites often called fool’s gold.  Some fossils can be preserved in this mineral.  Such fossils are very pretty when first collected but soon decay unless kept dry.

Back