The Table Mountain Sandstone (TMS) is a group of rock formations within the Cape Supergroup sequence of rocks. Although still widely used in common parlance, the term TMS is no longer formally recognized; the correct name is the "Table Mountain Group" (TMG). The sequence is dominated by quartzites of very low metamorphic grade and Ordovician age. The formation accumulated in a marine delta environment exposed to wave action on the margins of pre-Pangaean South Africa. The massive beds of sand have hardened to become an extremely weather-resistant sedimentary rock that is some two thousand metres thick in places. The rock forms tall crags that are a great favourite with local climbers.
The Cape Supergroup lies above an unconformity that separates it from the shales and hornfelses of the Malmesbury Formation and the intrusive Cape Granite, both of late Precambrian age. Many of the mountain ranges of the Western Cape are composed in the main of sandstones of the TMG. The old name, Table Mountain Sandstone, is derived from the famous landmark in Cape Town, Table Mountain. Formally-named formations within the TMG include the Graafwater Formation (sandstone, siltstone, shale), Peninsula Formation (quartizitic sandstone) and Pakhuis Formation (tillite).