the Brushy Canyon Formation. Rapid subsidence of the basin started in the middle Guadalupian. Patch reefs responded by rapid (mostly vertical) growth, resulting in the Goat Seep Reef. Three facies developed: Sediments deposited in a lagoon, forming the sandstones and dolomites of the Queen and Grayburg Formations. Sponge and algae skeletons accumulated near the Goat Seep Reef to become the Getaway Bank. Quartz sand laid down further in the basin became the Cherry Canyon Formation. Subsidence of the basin stopped for good by the later part of the Guadalupian. Capitan Reef was the largest in the basin, and it rapidly grew 350 miles (560 km) around it. The facies were: Fine-grained sand and carbonates deposited near the shore became the dolomites and sandstone of the Artesia Group. Offshore accumulations of sand and limey ooze in the basin were lithified into sandstone and limestone belonging to the Bell Canyon Formation. The Capitan Formation consists of Capitan Reef and is made of reef limestone. Capitan Reef was built primarily from calcareous sponges, encrusting algae such as stromatolites, and directly from seawater as a limey mud. In stark contrast, Cenozoic (current era), Mesozoic (age of the dinosaurs), and even middle Paleozoic (well before the Permian) reefs are mainly composed of corals. Sea level dropped as the late Permian glaciation intensified and locked increasing amounts of water in distant ice caps. Sedimentation continued to fill the Delaware Basin into the Ochoan Epoch of the upper Permian, periodically cutting the basin off from its source of seawater. Part of the resulting brine became the deep-water evaporites of the Castile Formation. The Castile consists of 1/16 inch (1.6 mm) thick laminae of alternating gray anhydrite and gypsum, brown calcite, and halite. As the salt concentration increased, halite and potassium-rich salt precipitated from the briny body of water on its margin and on nearshore areas. This salt layer covered an increasingly large area as the water level dropped, forming the Salado Formation. The Delaware Basin was filled at least to the top of Capitan Reef and mostly covered by dry land before the end of the Ochoan Epoch. Rivers migrated over its surface and deposited the red silt and sand that now constitute the siltstone and sandstone of the Rustler and Dewey Lake Formations. A karst topography developed as groundwater circulated in the buried limestone formations, dissolving away caverns which were later destroyed by infill and erosion.