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Gault Clay
The Gault Clay was formed during the Lower Cretaceous period about 100 million years ago. It rests on top of the Lower Greensand and so can be seen in Bedfordshire in the numerous sand quarries on the Greensand Ridge. When freshly quarried the clay appears to contain no fossils but as it weathers a diverse and rich fauna is slowly revealed.
The fossils of the Gault Clay include many of the groups familiar in the Jurassic. Ammonites are still common but some have now started to grow straight shells. These straight ammonites are called heteromorphs. As different ammonites lived at different times their fossil shells can be used to divide the clay into zones of different ages.
The Gault Clay contains layers of small phosphatic nodules. These were formed during times when sediment deposition was slow. The clay is used for the manufacture of pipes and tiles.
