The Tethys/"Proto-Tethys" was the vast ocean which lay between the Gondwanan continents and Europe/Asia from about 300 million years ago. The structures resulting from its closure remain today as the Caspian, Aral and Black seas and the Alps, Atlas and Himalaya mountains.

Along the Dorset coast Triassic, Jurassic and Cretaceous rocks are exposed, stacked in that order, but in the Mesozoic they were tilted slightly so that you can "walk through time" as you travel eastward. At Pinhay Bay, (west of Lyme Regis) red Rhaetic rocks are exposed showing that desert conditions existed then. Near Lyme, sharks, plesiosaurs and ichyosaurs have been found, not least by the collector, Mary Anning (b. 1799) who, with Joseph Anning found the first Ichthyosaur and many other notable fossils which she supplied to the famous geologists of the day. At Monmouth Beach limestones are exposed and anoxic shales which are source rocks for the Wytch Farm oilfield. They are subject to spontaneous combustion as the oxidation of pyrite to sulphate releases heat and causes "volcanos" when parts of the cliff catch fire spectacularly.

At Charmouth the Black Ven Marls of the Jurassic L. Lias are famous for ammonites and host haematite nodules and are overlain by the Belemnite Marls. As you go east, Golden cap lives up to its name. Below the cap, Eype clay has yielded ammonites with pleisosaur teeth marks in them and a 19 armed sun-star. Fault Corner exposes the Junction bed (between the Lower and Middle Jurassic). Past West Bay the Bridport Sands indicate a receeding sea and are a reservoir rock for Wytch Farm. At the top of the cliffs, the Inferior Oolite is a shallow warm water deposit with calcium carbonate ooliths and a rich fauna with echinoids etc. Overlying the Inferior Oolite is an interesting Fullers Earth which contains an active clay mineral, montmorillonite used for filtration and refining.

Melanie's talk was well illustrated with her own drawings of Jurassic animals and there were examples of fossils from her own collection.