Hunstanton cliffs,Norfolk,England. This cliff has three distinct layers of sedimentary rock. Lowest and nearest the beach is a sandstone known as carstone (brown,several metres thick),a coarse and gritty rock from the Lower Cretaceous. It contains large quantities of iron. Next is a thin layer of Hunstanton Red Rock (red,1.2 metres thick),a pink ferruginous (iron) limestone layer from the Lower Cretaceous. The topmost layer is Cenomanian chalk (white,several metres thick),from the Upper Cretaceous,contaning fine crystals of calcite (calcium carbonate). The Cretaceous Period lasted from 145 to 65 million years ago. Hunstanton is on the north Norfolk coast |