Dolomitic limestone platform. Expansion megapolygons in a marine platform formed from dolostone, a dolomitic form of calcium carbonate (limestone). This coastal marine platform has been formed by the action of waves from the sea, combined with the abrading effect of beach shingle. The polygonal shapes (expansion megapolygons) are thought to be due to the environment in which the rock formed. This formation, called the Flats, is in Kimmeridge Bay, Dorset, UK.