Engineering geology of British rocks and soils : Gault Clay

The Gault is a sequence of clays, mudstones and thin siltstones with bands of phosphatic nodules of Middle and Upper Albian age. Its outcrop stretches south-westward fron1 East Anglia through Wessex to west Dorset and surrounds the Weald in an arc from North East Kent westwards through Surrey to Hampshire where it turns south and returns· eastward through west and east Sussex. The Gault clay thickens to the south and reaches its maximum developlnent of over 100 m in the Weald and thins to the west as it passes into Hampshire and Dorset. The Gault clay contains both clay and non-clay mineralso The major non-clay minerals are quartz and calcite. Quartz usually makes up about 20% or more of the Gault and its distribution is fairly uniform. Calcite is present as fossil debris and as a cementing agent. The Gault is more calcareous in the north east than the south and west.