The Rock of Gibraltar is a monolithic promontory. The Main Ridge has a sharp crest with peaks over 400 m above sea level, formed by Early Jurassic limestones and dolomites.[5] It is a deeply eroded and highly faulted limb of an overturned fold. The sedimentary strata comprising the Rock of Gibraltar are overturned, with the oldest strata overlying the youngest strata. These strata are the Catalan Bay Shale Formation (youngest), Gibraltar Limestone, Little Bay Shale Formation (oldest), and Dockyard Shale Formation (age unknown). These strata are noticeably faulted and deformed.[6]