Geologic map of the Casius Quadrangle of Mars

The Casius quadrangle (30 degrees N to 65 degrees N lat; 240 degrees W to 300 degrees W long) is one of the northern tier of Lambert conformal sheets of the Mars Atlas. It consists of four distinctive physiographic regions: 1) part of the northern cratered plain which forms an incomplete annulus around the north polar region, 2) smooth lowland plains of Utopia Planitia across the central and southwestern part of the map, 3) mountainous terrain, in the Nilosyrtis Mensae region south of the lowland plains, consisting of distinct mountains with hummocky surfaces, and 4) cratered plateau in the southwest part of the map, forming the northern part of a large complex cratered region in the mid-latitudes of Mars. In the Casius quadrangle, the cratered plateau is broken by a set of linear to curved parallel-sided canyons on its northern margin.