The Polarstar Formation, a 1-km-thick argillite and sandstone unit, is the uppermost part of a thick Cambrian to Permian sedimentary sequence in the Ellsworth Mountains. The formation gradationally overlies the Whiteout Conglomerate, an Upper Carboniferous-Lower Permian glacial diamictite. The lower part of the Polarstar is mostly argillite, and the middle part consists of coarsening-upward cycles of argillite to sandstone. These cycles begin with lenticular bedding overlain by wavy and flaser bedding and end with ripple-laminated, fine-grained sandstone to cross-bedded, medium-grained sandstone. The upper part of the formation consists of fining-upward cycles of channel-form, cross-bedded, medium-grained sandstone overlain by fine-grained sandstone...