ABSTRACT
Stratified rocks may stay horizontal or they may be folded. Sedimentary rocks that remain more or less horizontal once the sea has retreated or after they have been uplifted form characteristic landforms (Table 4.1). If the beds stay flat and are not dissected by river valleys, they form large sedimentary plains (sediplains). Many of the flat riverine plains of the Channel Country, south-western Queensland, Australia, are of this type. If the beds stay flat but are dissected by river valleys, they form plateaux, plains, and stepped topography (Colour Plate 1, inserted between pp. 210-11). In sedimentary terrain, plateaux are extensive areas of low relief
that sit above surrounding lower land, from which they are isolated by scarps (see Figure 4.4, p. 97). They are normally crowned by a bed of hard rock called caprock. A mesa or table is a small plateau, but there is no fine dividing line between a mesa and a plateau. A butte is a very small plateau, and a mesa becomes a butte when the maximum diameter of its flat top is less than its height above the encircling plain. When eventually the caprock is eroded away, a butte may become an isolated tower, a jagged peak, or a rounded hill, depending on the caprock thickness. In stepped topography, scarps display a sequence of structural benches, produced by harder beds, and steep bluffs where softer beds have been eaten away (see Colour Plate 10, inserted between pp. 210-11).
