Beacon Group sediments, consisting of approximately 1425 m of Permian-Triassic graywacke sandstones, siltstones, shales, and coals, are well exposed in the Shackleton Glacier area. The strata have a terrestrial origin and are subdivided into five formations. In ascending order, the formations are Pagoda Formation, Mackellar Formation, Mt. Butters Formation (new name), Buckley Formation, and Mt. Kenyon Formation (new name). Numerous Jurassic diabase sheets, individually as thick as 300 m, have an aggregate thickness about equal to that of the sedimentary section. The rock succession is similar to Beacon and diabase rocks in adjacent areas along 800 km of the Transantarctic Mountains and Gondwana rocks of other southern continents.