Kata Tjuta, sometimes written Tjuṯa (Kata Joota), and also known as Mount Olga (or colloquially as The Olgas), are a group of large domed rock formations or bornhardts located about 365 km (227 mi) southwest of Alice Springs, in the southern part of the Northern Territory, central Australia. Uluru, 25 km (16 mi) to the east, and Kata Tjuta form the two major landmarks within the Uluru-Kata Tjuta National Park.
The 36 domes that make up Kata Tjuta cover an area of 21.68 km2 (8.37 sq mi), are composed of conglomerate, a sedimentary rock consisting of cobbles and boulders of varying rock types including granite and basalt, cemented by a matrix of sandstone.
The highest point, Mount Olga, is 1,066 m (3,497 ft) above sea level, or approximately 546 m (1,791 ft) above the surrounding plain (198 m (650 ft) higher than Uluru). Kata Tjuta is located at the eastern end of the Docker River Road.
The region surrounding Kata Tjuta lies in the Amadeus Basin, an intracratonic basin formed during the Adelaidian, roughly 850-800 mya. During the Petermann Orogeny, approximately 550 mya, an event known as the Woodroff Thrust, thrust granulite facies rocks northward over low-grade metamorphic rocks. The eventual erosion of the formation resulted in a molasse facies, or deposition in front of rising mountains, in this case the Petermann Orogeny, to create the deposit known as the Mount Currie Conglomerate. The Mount Currie Conglomerate is made predominately of basalt, porphyry, granite, gneiss and volcanic rock fragments with a matrix composed of angular quartz, microcline and orthoclase among other minerals.
Both Uluru and the Kata Tjuta are made of sediment originating in this Mount Currie Conglomerate and both have a chemical composition similar to granite. Scientists using Rb/Sr dating techniques to accurately date the rock have given it an age of 600 mya, matching the date of the Woodroof Thrust event. The actual fresh rock that makes up the Olgas and Uluru is medium to dark gray with green or pink hues in some laminae. The bright orange-red hue, for which the structures are noted, is due to a patina over finely divided feldspar coated in iron oxide.