Radholme quarry near Whitewell is an important geological site being in part a Carboniferous reef knoll rich in fossil crinoids. It also has a superb limekiln. 2011. BGS: Clitheroe Limestone Formation (knoll-reef) - Limestone. Sedimentary Bedrock formed approximately 343 to 352 million years ago in the Carboniferous Period. Local environment previously dominated by shallow carbonate seas. Setting: shallow carbonate seas. These rocks were formed in warm shallow seas with carbonate deposited on platform, shelf and slope areas; often rich in corals and shelly faunas. May include evaporites where seawater was trapped and salts concentrated by evaporation.