These were formed from sedimentary rocks of sandstone, limestone, and shale in uplifted seabeds. The interior is mostly limestone and Aquia Creek sandstone. The buildings are covered with thick white limestone or sandstone. Limestone, dolomite and bauxite are abundant. These valleys are underlain by limestone or dolomite. The landmark is a conical outcrop composed of interbedded Permian marine limestone and volcanic rocks. They are built of limestone, granite, and Rosendale cement. Cotswold stone is a yellow oolitic Jurassic limestone. Other areas saw extensive use of limestone, granite and flint. It was constructed of limestone and Aswan granite. The islands are composed of low coral limestone and sand. There are also reserves of limestone, marble and salt. Carbonation occurs on rocks which contain calcium carbonate, such as limestone and chalk. Such rivers are frequently found in regions with limestone geologic formations. Between the areas of chalk and limestone downland are clay valleys and vales.