Geological Guide to Burton Bradstock

Geological succession of Burton Bradstock

Burton Cliff is similar to East Cliff at West Bay but in its middle part the Bridport Sands are succeeded by the full thickness (3.7m) of Upper, Middle and Lower Inferior Oolite and a little of the Fuller's Earth. The Inferior Oolite is not safely accessible in the cliff, but large fallen blocks are present on shore, in these almost the full thickness of the unit can be studied. There is access to the beach near to the stream, the River Bride or Bredy, and 155m east of this point a fault down throwing eastwards cuts the cliff, dropping the Inferior Oolite capping sufficiently to bring in Fuller's Earth in a cliff top outcrop. Beyond the fault are the large fallen blocks of Inferior Oolite.

Inferior Oolite

The sandstone is blue-grey when unweathered but has a think weathered surface layer of yellow. Here, fine-grained pyrite is oxidised to limonite or goethite. The sands contain Belemnites and trace fossils and occasional moulds of Ammonites . Aragonite shells have been dissolved away.

Bridport sands

There is a smaller cliff just after these high cliffs at Burton, which is made of Forest Marble and Frome Clay, but it is much degraded at its base, as it is protected by a stretch of shingle, part of the Chesil beach. In this cliff, 200m east of the car park the Boueti Bed can be traced in eroded ground between the footpath and the cliff top. It yields the brachiopods Goniorhynchia boueti, Avonothyris, Digonella with bivalve and other fossils. In the cliffs below the Frome clay can be examined and it crops out in the low cliffs at Burton Common and Cliff end.

Frome clay