The cliff sections of the World Heritage coast expose the most complete succession through the terrestrial facies of the Trias in Europe. It includes muds deposited it in ephemeral playa lakes, sands deposited in shallow braided rivers and coarse pebble beds deposited by torrents that flowed northwards from the Variscan Mountains of northern France. The succession culminates in brackish-water lagoonal deposits that herald the transition to the marine environments of the Jurassic.
The original definition of the Kimmeridgian Stage included the whole of the Kimmeridge Clay Formation, but was based on incorrect ammonite identifications. The upper part of the formation, characterised by species of Pectinatites and Pavlovia, is now correlated with the Tithonian of the Mediterranean province and the Volgian of the Boreal province. The sections adjacent to the Kimmeridgian-Tithonian and Kimmeridgian-Volgian boundaries at Kimmeridge Bay are the most complete recorded to date in Europe.