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You are here: Story of the Jurassic Coast > Geology > Discover by Area > The Isle of Portland
The steep rise up to Portland from Chesil beach and the gentle slope downhill across Portland towards Portland Bill give a distinctive wedge shape to this wild and industrial island landscape. Portland’s wedge shape is the result of being situated on the southern side of the Weymouth anticline, which serves as a prime example of the global influence of plate tectonics.
The geology here is late Jurassic (150-145 million years old), recording a fall in sea levels and the transition from tropical seas to the swamps, forests, lagoons and salt flats that persist into the Early Cretaceous. Marine fossils are prominent from the Kimmeridge Clay and Portland Stone but the fossil forest is also exposed on the cliff top and within the Portland quarries. Dinosaur footprints have also been found exposed in blocks of quarried stone.
Portland Stone is an internationally important source of marine reptile fossils as well as an internationally important building resource.
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